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KCSE CHEMISTRY PAST QUESTIONS

K.C.S.E
CHEMISTRY
PAST PAPERS & MAKING SCHEME
PAPER 233/1, 233/2

Chemistry paper 233/1
K.C.S.E 1995 QUESTIONS

  1. The electron arrangement ions X3- and Y2- are 2, 8, and 2, 8, 8 respectively.
    (a) Write the electronic arrangement of the elements X and Y. (2 mks)
    (b) Write the formula of the compound that would be formed between X and
    Y.
  2. When bromine gas reacts with aqueous sodium hydroxide, the equilibrium represented by the equation: Br2 (aq) +2OH-(aq) Br-(aq) + OBR- (aq) + H2O is established.
    What observations would be made if a few drops of sulphuric acid were added to the equilibrium mixture? Explain.
    3 Calculate the amount of calcium carbonate that would remain if 15.0g of calcium carbonate were reacted with 0.2 moles of hydrochloric acid.
    The equation for the reaction is CaCO3 (g) + 2HCl CaCl2 (aq) + CO2 (g) + H2O (g) (C = 12.0 = 1.60, Ca = 40.0)
  3. In an experiment, soap solution was added to three separate samples of water. The table below shows the volumes of soap solution required to form lather with 1000cm3 of each sample of water before and after boiling.
    Sample I Sample II Sample III
    Volume of soap before water is boiled (cm3) 27.0 3.0 10.6
    Volume of soap after water is boiled 27.0 3.0 3.0 a) Which water sample is likely to be soft? Explain. (2mks)
    c) Name the change in the volume of soap solution used in sample III (1mk)
  4. a) Name one natural fibre.
    b) Give one advantage of synthetic fibres over natural fibres. (1mk)
  5. The table below gives some properties of gases D and E.
    Gas Density Effects of H2SO4(aq) Effects of NaOH(aq)
    D Lighter than air Reacts to form a salt Dissolves without reacting
    E Heavier than air Not affected Not affected.
    a) Describe how you would obtain a sample of E from a mixture of gases D
    and E. (2mks)
    b) Suggest a possible identity of gas D. Give a reason for your answer. (1mk)
  6. The curve below represents the variation of temperature with time when pure and impure samples of a solid were heated separately. Which curve sows the variation in temperature for the pure solid? Explain (2mks)
  7. The diagram below represents a set – up that can be used to prepare and collect oxygen. a) Write an equation for the reaction that takes place (1mk)
    b) What property of oxygen makes it possible for its collection as indicated
    by the diagram (1mk)
    c) Explain why it is important not to collect any gas for the first few. Seconds of the experiment. (1mk)
  8. Study the set – up below and answer the question that follows.

State and explain the observations that would be made when the circuit is completed.

  1. In an experiment, rods of metals P, Q and R were cleaned with sand paper and placed in a beaker containing water. Another set of rods was also cleaned and placed in a beaker containing dilute acid. After placing the rods in the two liquids bubbles of gas were seen around some of the rods as shown in the diagrams below.

a) Why is it necessary to clean the rods with sand paper before dipping them into the liquids. (1mk)
b) Arrange the three metals in order of their reactivity starting with the most reactive.

  1. A Solution of chlorine in tetra chloromethane turns colourless when propene gas is bubble though it.
    a) What type of reaction takes place? (1mk)
    b) Write an equation for the above reaction (1mk)
  2. With reference to atomic number of one, explain why hydrogen can be placed in either group I and VII of the periodic table. (2mks)
  3. a) Explain why it is not advisable to use wood ash for cleaning aluminium
    Utensils (2mks)
    b) Duralumin is an alloy of aluminium. What is the advantage of using duralumin in place of aluminium for manufacture of aeroplane parts. (1mk)
  4. A compound has an empirical formula, C3H6O and a relative formula mass of 16. Determine its molecular formula (H + 1.0, C = 12.0, O = 165.0) (2mk)
  5. Explain how you would separate mixture of nitrogen and oxygen gases given that their boiling points are – 196oC and 183OC respectively (2mks)
  6. Study the table below and answer the questions that follow.
    Alkane Formula Heat of combustion (Hc) kJmol -1
    Methane
    Ethane
    Propane
    Butane CH4
    C2H6
    C3H6
    C4H10 890
    1560
    2220
    a) Predict the heat of combustion of butane and write it on the space provided in the table above? (1mk)
    b) What does the sign of Hc value indicate about combustion of alkenes? (1mk)
  7. The diagram below represents the extraction of sulphur by Frasch process a) Name the substance that passes through tube;
    I
    II
    b) What is the purpose of hot compressed air in this process? (1mk)
  8. Study the diagram below and answer the questions that follow.

Write an equation for each of the two reactions that take, place in the experiment represented by the diagram above (2mks)

  1. A mixture containing equal volumes of hydrogen and carbon dioxide was introduced one end of a tube as shown below. Which gas would be detected at appoint C in first? Explain (2mks)
  2. The table below gives three experiments on the reaction of excess sulphuric acid and 0.5g of zinc done under different conditions. In each the volume of gas was recorded at different time intervals.
    Experiment Form of Zinc Sulphuric acid solution
    I Power 0.8m
    II Power 1.0m
    III Granules 0.8m
    On the axis below draw and label the three curves that could be obtained from such results.
  3. The table shows how solubility of some substances in water varies with temperature.
    Substance Change of OoC Solubility 20o C With temperature 40oC (g/100cm3 of water) 60oC
    W
    X
    Y 0.334
    27.60
    35.70 0.16
    34.0
    36.0 0.097
    40.0
    36.6 0.0058
    45.5
    37.3
    Which of the above substances is likely to be a gas? Explain (2mks)
  4. Dilute nitric acid reacts with copper according to the equation;
    3CU(s) + 8H + (aq) + 2N-3 3Cu2+ (aq) + 2NO (g) + 4H2O (l)
    a) What is the oxidation number of nitrogen in?
    i) 2N-3
    ii) NO
    b) With respect to nitrogen, explain whether the above reaction is an oxidation or reduction process. (1mk)
  5. Explain the following observation. A chloride dissolves in water to form an electrolyte while the same chloride dissolves in methylbenzene to for a non – electrolyte. (1mk)
  6. State what would be observed when dilute hydrochloric acid is added to the products formed when a mixture of iron fillings and sulphur? (1mk)
  7. Describe how the following reagents can be used to prepare lead sulphate solid potassium sulphate, solid lead carbonate, dilute nitric acid and distilled water.
  8. Explain why the enthalpy of neutralization of ethanoic acid with sodium hydroxide is different from that of hydrochloric acid with sodium hydroxide. (2mks)
  9. Give a reason why calcium hydroxide solution is used to detect the presence of carbon dioxide gas while sodium hydroxide in NOT?
    28 a compound C4H10O_ is oxidized by excess acidified potassium permanganate to form another compound C4H8O2. The same compound C4H10O reacts with potassium to produce hydrogen gas.
    a) Draw the structural formula and name the compound CaH10O (1mk)
    b) Write an equation for the reaction between potassium and compound
    C4H10O.
  10. During the production of hydrogen iodide, hydrogen reacts with iodine according to the equation: H2 (g) + I2 (g) 2HI (g); 52.0 kJ
    Explain how the following would affect the yield of hydrogen iodide:
    a) Increase in temperature
    b) Increase in pressure. (2mks)
  11. a) 100gm of radioactive 233 Pa was reduced to 12.5g after 81 days.
    91
    Determine the half-life of Pa. (2mks)
    b) 233 Pa decays by beta emission. What is the mass number and
    91
    Atomic number of the element formed? (1mk)

CHEMISTRY K.C.S.E 1995 PAPER 233/2
QUESTIONS

  1. The table below gives information on four elements by letters K, L, M and N. Study it and answer the questions that follow. The letters do not represent the actual symbols of the elements.

Element Electron arrangement Atomic radius (nm) Ionic radius(nm)
K
L
M
N 2, 8, 2
2, 8, 7
2, 8, 8, 1
2, 8, 8, 2 0.136
0.099
0.203
0.174 0.065
0.181
0.133
0.099

a) Which two elements have two similar properties? Explain (2mks)
b) What is most likely formula of oxide of L? (1mk)
C) Which element is a non-metal? Explain (1 mk)
d) Which one of elements is the strongest reducing agent? Explain (2mks)
e) Explain why ionic radius of N is less than that of M (2mks)
f) Explain why the ionic radius of L is bigger than its atomic radius (2mks)
2 a) IN an experiment hydrogen chloride gas was prepared and reacted with
aluminium turnings to form a solid q and gas R as shown in the diagram below.

(i) Name: Liquid P
: Solid Q (1mk)
: Gas R (1mk)

(ii) Name another substance that could serve the same purpose as the concentrated sulphuric acid. (1mk)

(iii) Explain the following observation. When blue litmus paper was dipped into the water in the beaker at the end of the experiment it turned red.
Explain why solid Q collects farther away from the heated aluminium (2mks)
(b) (i) Write an equation for the reaction that takes place between ammonia gas
and hydrogen gas (1mk)
(ii) Calculate the mass of the product that would be formed when 2000cm3 of
hydrogen chloride gas reacts completely with excess ammonia gas
(H=1, O; N= 14.0, C1 = 35.5, one mole of gas occupied 24 litres at room temperature and pressure.) (3mks)

  1. In an experiment to determine the heat of combustion of methanol, CH2OH a student used a set up like the one shown in the diagram below. Volume of water = 500cm3
    Final temperature of water= 27.00C
    Initial temperature of water = 20.00C
    Final mass of lamp + methanol = 22.11g
    Initial mass of lamp+ methanol= 22.98g
    Density of water = 1.0g cm3 a) Write an equation for the combustion of methanol
    b) Calculate:
    (i) The number of moles of methanol used in this experiment
    (C = 12; O = 16; H = 1)
    (ii) The heat of combustion per mole of methanol. (1mk)
    (iii) The heat of combustion per mole of methanol (2mks)
    (c) Explain why the value of the molar heat of combustion for methanol obtained in this experiment is different from the theoretical value.
    (d) On the axis below draw an energy level diagram for the combustion of methanol.
  2. a) The flow chart below outlines some of the process involved during
    extraction of copper from copper pyrites. Study it and answer the questions that follow.

(i) Name gas K (1mk)
(ii) Write an equation for the reaction that takes place in the 1st roasting furnace. (1mk)
(iii) Write the formula of the cation present in slag M (1mk)
(iv) Identify gas p (1mk)
(v) What name is given to the reaction that takes place in chamber N? Give a reason for the answer. (1mk)
(b) The copper obtained from chamber N is not pure. Draw a labeled diagram to show the set up you would use to refine the copper by electrolysis. (3mks)
(c) Given that the mass of copper obtained from above extraction was 210kg, determine the percentage purity of the ore(copper pyrites) if 810kg of it was fed to the 1st roasting furnace. (Cu = 63.5, Fe = 56.0, s=32.0) (3mks)
(d) Give two effects that this process could have on the environment (2mks)

  1. The flow charts below show an analysis of a mixture R that contains two salts. Study the analysis and answer the questions that follow. (a) (i) What condition is necessary for the process in step I to take place? (1mk)
    (ii) Draw a labeled diagram for the set-up that could be used to separate the mixture formed in step II (2mks)
    (iii) Write ionic equation for the reaction between the cation in filtrate X and aqueous ammonia. (1mk)
    (iv) What observation would indicate the presence of NO2 (g) in step I
    (v) State how water vapour, in step I could be identified. (1mk)
    (b)

(i) What conclusion can be drawn from step iV only? Explain? (2mks)
(ii) Write the formula of an anion present in the residue U. Explain (2mks)
(iii) Suggest the identity of the cation present in solution z. (1mk)

(c) Name the two salts present in the mixture R. (2mks)

  1. (a) The table below gives information about the major constituents of crude
    oil. Study it and answer the questions that follow.
    Constituent Boiling point (0C)
    Gases
    Petrol
    Kerosene
    Diesel oil
    Lubricating oil
    Bitumen. Below 40
    40-175
    175-250
    250-350
    350-400
    Above 400

(i) Which one of the constituents or crude oil has molecules with the highest number of carbon atoms? (2mks)
(ii) Name the process you would use to separate a mixture of petrol and diesel and explain how the separation takes place. (2mks)
(iii) Explain why the constituent of crude oil and write its formula (1mk)
(iv) Name one gas that is likely to be a constituent of crude oil and write its formula. (1mk)
(b) What condition could cause a poisonous gas to be formed when Kerosene is burnt? Explain (2mks)
(c) Give one use of bitumen (1mk)

  1. (a) The diagram below shows a set-up that can be used to obtain nitrogen gas
    in an experiment. (i) Name liquid L (1mk)
    (ii) What observation would be made in tube K after heating for some time? (1mk)
    (iii) Write an equation for the reaction that took place in tube K. (1 mk)
    If 320 cm3 of ammonia gas reacted completely with the copper?
    Calculate:
    I Volume of nitrogen gas produced. (1mk)
    II the mass of copper oxide that reacted (3mks)
    (Cu = 63.5, O=16.O, one mole of gas occupies 24 liters at room temperature and pressure)
    (v) At the end of experiment the PH of the water in the beaker was found to be about
    1) Explain (2mks)
    (b) In another experiment a gas jar containing ammonia was inverted over a burning splint. What observation would be made? (1mk)
    (c) Why is it advisable to obtain nitrogen from air instead ammonia? (1mk)

KCSE 1996 CHEMISTRY PAPER 233/1
QUESTIONS

  1. In an experiment to study the diffusion of gases, a student set up the apparatus shown in diagram 1. After sometime the student noticed a change in the water level as shown in the diagram Give an explanation for the change in water level (2mks)
  2. A fixed mass of a gas has a volume of 250cm3 at a temperature of 270C and 750mm Hg pressure. Calculate the volume the gas would occupy at 420C (2mks)
  3. Zinc metal and hydrochloric acid reacts according to the following equation
    Zn(s) + 2HCI (aq) ZnCI2 (aq) + H2 (g)
    1.96 g of zinc were reacted with 100cm3of 0.2M hydrochloric acid
    (a) Determine the reagent that was in excess
    (b) Calculate the total volume of hydrogen gas was liberated S.T.P
    (Zn= 65.4 Molar gas volume = 22.4 litres at S.T.P (1mk)
  4. Ammonia can be converted to nitrogen monoxide as shown in the equation below
    4NM3 (g) + 5O2 (g) 4NO (g) + 6H2O (I) (a) Explain how an increase in temperature would affect the yield of nitrogen
    monoxide (2mks)
    b) On the energy level diagram above sketch, the energy level diagram that would be
    obtained if the reaction is carried out in the presence of platinum catalyst. (1 mk)
  5. a) Using dots(.) and crosses (x) to represent electrons draw diagram to represent the
    bonding in:
    (i) NH3 (ii) NH4+ (1mk)
    b) State why an ammonia molecule (NH3) can combine with H+ to form NH4+ (Atomic numbers: N=7 and H=1) (1mk)
  6. The table below shows some properties of substances E, F, G and H
    Substance Action with water Melting point Thermal conductivity
    E
    F
    G
    H Un reactive
    Reactive
    Unreactive
    Unreactive High
    High
    High
    Low Poor
    Poor
    Good
    Good
    Select the substance that would be most suitable
    a) For making a cooking pot (1mk)
    b) As a thermal insulator (1 mk)
  7. The reaction of propane with chlorine gas gave a compound of formula C3H7Cl.
    a) What condition is necessary for the above reaction to take place? (1mk)
    b) Draw two structural formulae of the compound C3H7Cl (2mks)
  8. A sample of air contaminated with carbon monoxide and sulphur dioxide was passed
    through the apparatus shown in the diagram below. Which contaminant was removed by passing the contaminated air through the apparatus
    Explain . (2mks)
  9. Explain how a sample of CH3CH2CH2OH, could be distinguished from a sample of
    CH3COOH by means of a chemical reaction (2mks)
  10. a compound whose structure is shown below is found in a detergent.

With reference to the structure, explain how the detergent removes grease during washing.
(2mks)

  1. Complete the table below.
    Species Number of neutrons Electrons
    H
  2. When magnesium metal is burnt in air, it reacts with both oxygen and nitrogen gases
    giving a white ash. Write two equations for the reactions that take place. (2mks)
  3. Methane reacts with oxygen as shown by the equations I and II below:
    I CH4(g) + 2O2(g) CO2(g) + 2H2O(l)
    II 2CH4(g) + 302(g) 2CO(g) + 4H2O(l)
    Which one of the two reactions represents the complete combustion of methane? Explain
    (2mks)
  4. The decomposition of calcium carbonate can be represented by the equation:
    CaCO3(s) __ CaO(s) + CO2 (g)
    Explain how an increase in pressure would affect the equilibrium position (2mks)
  5. The table below gives the atomic numbers of elements W, X, Y, and Z. The letters do
    not represent the actual symbols of the elements.

Element W X Y Z
Atomic Number 9 10 11 12

a) Which one of the elements is least reactive? Explain (1mk)
b) i) Which two elements would react most vigorously with each other? (1mk)
ii) Give the formula of the compound formed when the elements in b(i) react
(1mk)

  1. On strong heating, sodium nitrate oxygen gas. In the spaces provided below, draw a
    labeled diagram of a set-up that could be used for heating sodium nitrate and collecting the oxygen gas liberated. (3mks)
  2. Oxygen reacts with the elements phosphorous, sulphur and chlorine to from oxides oxide
    of sulphur and its highest oxidation number. Complete the table for phosphorus and chlorine. (Atomic numbers: P=15, S= 16 Cl = 17)

Element Oxide Highest oxidation number
P
S
Cl _
SO3


_________
     46

  1. Explain why it is not advisable to use aqueous chloride solution as the salt bridge in the
    electrochemical cell formed between half cells, Pb2-(aq)/pb(s) E0 = 0.13V and
    CU2 + (aq) + (aq)/CU2+(aq)/Cu2(s) E0=0.34V (2mks)
  2. Use the information below to answer the questions that follow:
    Equation Enthalpy of formation
    H2 (g) + ½ O2 (g)  H2O (l) H1= -286 kjmol-1
    C(s) + O2 (g) CO2 (g) H2= 394kjmol
    2C(s) + 3H2 (g) ½ O2 +  C2H5OH (i); H3=277kjmol-1
    a) Define the term “enthalpy of formation of a compound (1mk)
    b) Calculate the molar enthalpy of combustion,  H3 of ethanol:
    C2H5OH (l) + 302(g) 2CO2 (g) +3H2O (l) (2mks)
  3. Complete the diagram below to show how  and  particles from a radioactive source
    can be distinguished from each other. Label your diagram clearly (3mks)
  4. Chlorine and iodine are elements in the same group in the periodic table. Chlorine gas is
    yellow white aqueous, iodine; I2(aq) is brown.
    a) What observation would be made if chlorine gas is bubbled through aqueous
    sodium iodide? Explain using and ionic equation. (2mks)
    b) Under certain conditions chlorine and iodine react to give iodine chloride, ICl3(s)-
    What type of bonding would you expect to exist in iodine trichloride? Explain (1mk)
  5. The diagram below represents a set-up that was used to react lithium with water study it
    and answer the questions that follow:

a) Write an equation for the reaction that takes place; given that the atomic number of lithium is 3. (1 mk)
b) Why would it not be advisable to use potassium in place of lithium in the above set-up? (1mk)

  1. Explain how you would obtain solid carbonate from a mixture of lead carbonate and sodium carbonate powders. (3mks)
  2. In an experiment, 2.4g of sulphur was obtained by reacting hydrogen sulphide and chorine as shown by the equation below:
    H2S (g) + Cl2 (g)  S(s) + 2HCl (g)
    (a) Which of the reactants acts as a reducing agent in the above reaction? Explain.
    (1 mk)
    (b) Given that the yield of sulphur in the above reaction is 75%, calculate the number
    Of moles of H2S (g) used in the reaction (S=32.0)
  3. A polymer has the following structure:
    -CH2 – CH-CH2-CH-CH2 –CH CN CN CN

A sample of this polymer if found to have a molecular mass of 5194. Determine the number of monomers on the polymer (H=1.0, C= 12.0, N = 14.0)

  1. Study the chart below and a answer the questions that follow: a) Identify i) The metal ions in solution K (1mks)
    ii) The white precipitate L (1mk)
  2. Study the flow chart below and answer the questions that follow a) Name i) Compound T (1mk)
    ii) Gas U (1mk)
    b) Give a chemical test that you could use to identify gas U (1mk)
  3. A mixture of pentane and pentanoic acid was shaken with 0.1M sodium hydroxide solution and let to separate as shown in the diagram below: Name the main component in layer W.Give a reason for the answer (2mks)
  4. Write an equation for the reaction that takes place when carbon monoxide gas is passed over heated lead (II) oxide. (1mks)

K.C.S.E 1996 CHEMISTRY PAPER 233/2
QUESTIONS

  1. Sodium thiosulphate solution reacts with dilute hydrochloric acid according to the following equation.
    S2O32- (aq) + 2H+ (aq) H2O (l) + SO2 + S(s)
    In an experiment to study how the rate of reaction varies with concentration,
    10cm3 of 0.4M sodium thiosulphate was mixed with 10cm3. Of 2M hydrochloric acid in a flask. The flask was placed in a white paper marked with across X.The time taken for the cross X become invisible when viewed from above was noted and recorded in the table below. The experiment was repeated three times as the temperature using the volumes in the table and the results recorded as shown in the table below.
    Experiment Volume of 0.4M thiosulphate (cm3) Volume of
    water (cm3) Volume of 2M HCl(cm3) Time (Sec)
    1 10 0 10 16
    2 7.5 2.5 10 23
    3 5.0 5.0 10 32
    4 2.5 7.5 10 72
    a) i) On the grid below, plot a graph of the volume of thiosulphate (Vertical
    axis) against time taken for the cross (X) to become invisible)
    ii) From the graph determine how long it would take for the cross to become invisible if the experiment was done. (3mks)
    i) Using 6cm3 of the 0.4M thiosulphate (1mk)
    ii) Using 6cm3 of 0.2M thiosulphate solution (1mk)
    b) i) Using values for experiment I.Calculate
    i) Moles of thiosulphate used (1mk)
    ii) Moles of hydrochloric acid used (1mk)
    ii) Explain which of the two reactants in experiment I controlled the rate of the reaction? Explain (1mk)
    c) Give two precautions which should be taken in experiment I controlled the rate of the reaction? Explain (2mk)
  2. a) The diagram below shows incomplete set – up of the laboratory and
    preparation collection of chlorine gas. Study it and answer the questions that follow. i) Complete the set – up to show how dry chloride gas may be collected. ii) The equation for the redox reaction that takes place is MnO2(s) + 4 HCl (aq) MnCl2 (aq) + 2H2O (l) + Cl2 (g) Explain, using oxidation numbers, which species is reduced (2mks) iii) What is the purpose of water in flask L? (1mk) b) Study the diagram below and answer the questions that follow.

When some hydrogen chlorides gas is allowed into water and the mixture stirred, the bulb lights and gases X and Y are formed.
i) Name: Gas X
Gas Y
ii) Explain why the bulb does not light before the hydrogen chloride
gas is let into water. (2mks)
iii) Explain using equations why the volume of gas X is less than that of gas (2mks)

  1. The extraction of a luminium from it s ore takes place in two stages, purification stage and electrolysis stage. The diagram below shows the set – up for the electrolysis stage. a) i) Name the ore from which aluminium extracted. (1mk)
    ii) Name one impurity, which is removed at the purification stage.(1mk)
    b) i) Label on the diagram each of the following
    i) Anode
    ii) Cathode
    iii) Region containing the electrolyte.
    ii) The melting point aluminium oxide is 2054oC, but electrolysis is carried out between 800 – 900oC.
    i) Why is the electrolysis not carried out at 2054oC (1mk)
    ii) What is done lower the temperatures? (1mk)
    iii) The aluminium which is produced is tapped off as aliquid. What does this suggest about it smelting point? (1mk)
    c) A typical electrolysis cell uses current of 40,000 amperes.Calulate the mass (in kilograms) of aluminium produced in one hour) (3mks)
  2. Study the table below and answer the questions that follow:

Element Atomic number Relative atomic mass Melting point (oC)
Aluminium
Calcium
Carbon
Hydrogen
Magnesium
Neon
Phosphorous
Sodium 13
20

12
10
15 27.0
40.0
12.0
1.0
24.3

31.0
23
850
3730
-259
650
-249
44.2 (white)
590 (red)

a) Complete the table by filling in this missing atomic numbers and atomic mass.
(2mks)
b) Write the electron arrangement for the following ions (2mks)
Ca+
P3+
c) What is the melting point of hydrogen in degrees Kelvin? (1mk)
d) Which of the allotropes of phosphorous ha a higher density? Explain (2mks)
e) The mass numbers of three isotopes of magnesium are 24, 25 and 26.
What is the mass number of the most abundant isotope of magnesium? Explain
(2mks)
f) Give the formula of the compound formed between aluminium and carbon.(1mks)
g) Explain the difference in the melting points of magnesium and sodium.(2mks)

  1. a) Study the table below and answer the questions that follow.
    Compound Melting point(oC) Boiling point (oC)
    C2H4O2
    C3H6
    C3H8O
    C5H12
    C6H14 16.6
    -185
    -127
    -130
    -95.3 118
    -47.7
    97.2
    36.3
    68.7

i) Which of the compounds is a solid at 10.0oC? Explain (1mk)
ii) Choose two compounds which are members of the same homologous series and explain the difference in their melting points. (3mks)
iii) The compound C3H8O is an alcohol. How does its solubility in water differ from the solubility of C5H12 in water? Explain. (2mks)
b) Complete combustion of one mole of a hydrocarbon produced four moles of carbon dioxide and four moles of water only.
i) Write formula of the hydrocarbon (1mk)
ii) Write the equation for the combustion reaction: (1mk)
c) In a reaction, an alcohol J was converted to a hex- 1 – ene.
i) Give the structural formula of the alcohol J
ii) Name the reagent and conditions necessary for the reaction in c (i) above
d) Compound K reacts with sodium hydroxide as shown below? (1mk)

i)  What type of reaction is represented by the equation above?         (1mk)
ii) To what class of organic compounds does K belong?           (1mk)
  1. a) Give the name of each of the processes described below which takes place when
    salts are exposed to air for sometime.
    i) Anhydrous copper sulphate becomes wet (1mk)
    ii) Magnesium chloride forms an aqueous solution (1mk)
    iii) Fresh crystals of sodium carbonate, Na2CO3. 10H2O (1mk)
    b) Write the formula of the complex ion formed in each of the reactions described
    below.
    (i) Zinc metal dissolves in hot alkaline solution (1mk)
    (ii) Copper hydroxide dissolves in excess ammonia solution. (1 mk)
    (c) A hydrated salt has the following composition by mass. Iron 20.2% Oxygen
    23.0%, sulphur 11.5%, water 45.3 %. Its relative formula mass is 278.
    (i) Determine the formula of the hydrated salt.. (3mks)
    (Fe=56, S=32; O = 16, H =1)
    (ii) 6.95gm of the hydrates salt were dissolved in distilled water and the total volume
    made to 250 cm3 of solution. Calculate the concentration of the salt solution in moles per litre.
  2. (a) The graph below shows the solubility of sulphur dioxide gas at different temperatures. Use the following in it to answer the questions that follow. (i) From the graph determine:
    I The lowest temperature at which 1,000cm3 of solution would contain 116g of sulphur dioxide.
    II The maximum mass of sulphur dioxide that would dissolve in 15 litres of solution at 100C
    (ii) Sodium hydroxide reacts with sulphur trioxide according to the following equation.
    2NaOH(aq) +SO2(g) Na2SO3(aq) + H2O(l)
    Using the information in the graph determine the volume of 2M sodium hydroxide required to completely neutralize on one litre of saturated sulphur dioxide solution
    230C. (S=32.0; O; O = 16.0) (3mks)

(b) Study the flow chart below and answer the questions that follow.

Write equation for the reaction taking place at:
I The roasting furnace (1mk)
II The absorption tower (1mk)
III The diluter (1mk)
The reaction taking place in chamber K is
SO2 (g) + 1/2O2 (g) SO3 (g)

I Explain why it is necessary to use excess air in chamber K
II Name another substance used in chamber K
(c) Study the scheme given below and answer the questions that follow:

(i) Name the reagents used in:

Step I……………… (1mk)
Step II……………… (1mk)
Step IV…………… (1mk)

(ii)    Write an equation for the complete combustion of CH = CH (1mk)

Explain one disadvantage of the continued use of items made from the compound formed in step III (2mks)

CHEMISTRY PAPER 233/1 K.C.S.E 1997
QUESTIONS.

  1. The set – up below was used to study some properties of air. State and explain two observations that would be made at the end of the experiment.
  2. When extinguishing a fire caused by burning kerosene, carbon dioxide is used in preference to water .Explain
  3. Complete the table below by inserting the missing information in the space provided.
    Name of polymer Name of monomer One use of the polymer Vinyl chloride
    (Chloroethane)
  4. When dilute nitric acid was added to a sample of solid C, a colourless gas that formed a white a white precipitate with limewater was produced. When another sample of solid C was heated strongly in a dry test – tube, there was no observable change.
  5. The structure shown below represent two cleansing agents, A and B
    R — COO — Na+ OSO3-Na+

Which cleansing agent would be more suitable for washing in water containing magnesium sulphate?

Give a reason
  1. Study the set – up below and answer the questions that follow.
    Diagram a) What observation would be made in the tube?
    b) Indicate with across (x) on the diagram the likely position where the observation
    stated in (a) above would be made.
    NB. Not to touch the cotton wool.
  2. M grammes of a radioactive isotope decayed to 5 grammes in 100 days.
    The Half – lift off the isotope is 25 days.
    a) What is meant by half – life?
    b) Calculate the initial mass of M of the radioactive isotope.
  3. The empirical formula of a hydrocarbon is C2H3.The hydrocarbon has
    a relative molecular mass of 54..(H = 1.0, C = 12.0).
    a) C2H3
    b) Draw the structural formula of the hydrocarbon
    c) To which homologous series does the hydrocarbon drawn in (b) above belong?
  4. Potassium sulphite solution was prepared and divided into two portions. The first portion gave a white precipitate when reacted with barium nitrate. On addition of dilute hydrochloric acid the white precipitate disappeared.
    a) Write the formula of the compound which formed as the white precipitate.
    b) Write the equation for the reaction between dilute hydrochloric acid and the compound whose formula is written in (a) above.
    c) What observation would be made if one drop of potassium dichromate
    solution was added to the second portion followed by dilute hydrochloric acid?
  5. 0.63g of lead powder were dissolved in excess nitric acid to form lead nitrate
    solution. All the lead nitrate solution was reacted with sodium sulphate solution.
    a)Write an ionic equation for the reaction between lead nitrate and sodium
    sulphate solutions.
    b) Determine the mass of the lead salt formed in (a) above.
    (Pb = 207, S = 32.0 = 16)
  6. Explain why anhydrous magnesium chloride is fairly soluble in organic solvents while anhydrous magnesium chloride is insoluble.
  7. Name and draw the structure of the compound formed when methane reacts with excess chlorine in the presence of U.V light.
  8. Sulphur burns in air to form sulphur dioxide.A simple energy level diagram for the reaction is given below. Study the diagram and answer the questions that follow.

a) What do the following represent?
b) Write an expression, for H3 in terms of H1 and H2

  1. In an experiment, chlorine gas was passed into moist hydrogen sulphide contained in a boiling tube as shown in the diagram a) What observation was made in the boiling tube?
    b) Write an equation for the above reaction.
    c) What precaution should be taken in carrying out this experiment? Give a reason.
  2. Complete the diagram below to show how a sample of aqueous ammonia can be prepared in the laboratory.
  3. A gas occupies a volume of 400cm3 at 500k and 1 atmosphere pressure.
    What will be the temperature of the gas when the volume and pressure of the gas is 100cm3 and 0.5 atmospheres respectively.
  4. In an equation below, identify the reagent that acts as abase. Give a reason.
    H2O(aq) + H2O(l) H3O(aq) + HO2-(aq)
  5. Study the scheme below and answer the questions that follow. a) Write the formula of the caution present in solution F.
    b) What property of chlorine is shown in step I
    c) Write an equation for the reaction which occurs in step III
  6. 90cm3 of 0.01M calcium hydroxide were added to a sample of water containing 0.001 moles of calcium hydrogen carbonate.
    a) Write an equation for the reaction which took place
    b) Calculate the number of moles of calcium ions in 90cm3 of 0.01M
    calcium hydroxide.
    c) What would be observed if soap solution was added drop wise to a sample
    of the water after the addition of calcium hydroxide? Give a reason.
  7. When 0.6g of element J were completely burnt in oxygen and all the heat evolved was used to heat 500cm3 of water, the temperature of the water rose from 23oC to 32OC. Calculate the relative atomic mass of element J given that the specific heat capacity of water = 4.2JK-1g-1, density of water = 1.0g/cm3 and molar heat is combustion of J is 380Kjmol-1
  8. A student set up the experiment below to collect gas K the glass wool was heated before heating the Zinc powder. Why was it necessary to heat the moist glass wool before heating zinc powder
  9. In an experiment to separate a mixture of two organic liquids, liquid M (b.p 56oC)
    And liquid (b.p. 118oC), a student set up the apparatus shown below. a) Identify two mistakes in the set – up
    b) What method would the student use to test the purity of the distillates obtained?
  10. An element Y has the electronic configuration 2.8.5
    a) Which period of the periodic table does the element belong?
    b) Write a formula of the most stable anion formed when element Y ionizes
    c) Explain the difference between the atomic radium of element Y and
    its ionic radius.
  11. Aqueous potassium sulphate was electrolysed using platinum electrodes in a cell.
    a) Name the products formed at the cathode and anode.
    Anode b) How does the concentration of the electrolyte change during electrolysis.
    c) Why would it not be advisable to electolyse aqueous potassium sulphate
    using potassium metal electrodes.
  12. The information below relates to element L, Q,R and T.The letters do not represent the actual symbols of the elements. Arrange the elements in
    2Q-(aq) +R2(aq) Q2(g) + 2r(aq)
    2T-(aq) + Q2(g) 2Q-(aq) + T2(g)
    L-(aq) + R2(g) no reaction
    a) Give the formula of an oxide which reacts with both dilute hydrochloric
    acid and hot concentrated sodium hydroxide.
    b) Give the formulae of the products formed when the oxide in (a) above reacts
    with excess hot concentrated sodium hydroxide.
  13. Using dots (.)and crosses (x) to represent outermost electrons, draw diagrams to show the bonding in CO2 and H3O+ (Atomic numbers; H = 1.0,C= 14.0, O = 8 ).
  14. Calculate the mass of nitrogen dioxide gas that would occupy the same volume as 10g of hydrogen gas at same temperature and pressure.(H = 1.0, N = 14.0, o = 16.0)

CHEMISTRY PAPER 233/2 K.C.S.E 1997
QUESTIONS
Use standard electric potentials for elements A, B,C, D and F given below to answer the questions that follow.

Eθ ( Volts)
A2+ (aq) + 2e A (s) – 2.90

B2+(aq) + 2e            B (s)        -2.38

C+ (aq) + 2e            C (g)       - 0.00

D2+ (aq) + 2e           D (s)       + 0.34

½ F2 (g) + e            F- (aq) +2.87

Which element is likely to be hydrogen? Give a reason for your answer
What is the Eθ value of the strongest reducing agent?
In the space provided draw a labeled diagram  of the electrochemical cell that  would be obtained  when  half – cells of elements  B and  D are combined
Calculate the Eθ value of the electrochemical cell constructed in (iii)  above
During the  electrolysis of aqueous copper (II) sulphate using copper electrodes, a current of 0.2 amperes was passed through the cell for 5 hours
Write an ionic equation for the reaction that took place at the anode
Determine the change  in mass of  the anode which occurred as a result of the electrolysis process

(Cu= 63.5, 1 Faraday = 96,500 coulombs.

(a) Give the names of the following compounds
CH3CH2CH2CH2OH
CH3CH2COOH
CH3C-O-CH2CH3

(b) Study the information in the table below and answer the questions that follow

Number of carbon atoms per molecule Relative molecular mass of hydrocarbon
2
3
4 28
42
56
Write the general formula of the hydrocarbon in the table
Predict the relative atomic mass of the hydrocarbon with 5 carbon atoms
Determine the molecular formula of the hydrocarbon in (ii) above and draw its structural formula (H = 1.0 C= 12.0)

Study the scheme given above and answer the questions that follow

















Name the  reagents used in:

Step I …………………….
Step II ……………………..
Step III ……………………..
Write an equation for the complete combustion of CH = CH

Explain one disadvantage  of the continued  use of items made from the compound formed  in step III

(a)     Study the information below and answer the questions that follow:
    The letters do not represent the actual symbols of the elements

Element Atomic
Number Melting Point
Element Formula of
Chloride Melting Point
Chloride
G
H
J
K
L 11
12
14
16
20 98
650
1410
113
851 GCI
HCI2
JCI4
K2CI2
LCI2 801
715
-70
-80
780
Which elements are metals? Give a reason
Write the formula of the compound formed when element H reacts with elements K
Explain why the melting point of J is higher than that of K
What is the oxidation state of J in its chloride
How does the:
I – Melting point of fluoride of G compare with that of its chloride?
II- Reactivity of H and L with water compare? Give an explanation (2mks)

(a) The diagram below  shows the extraction of sodium metal using the downs 
  cell. Study it answer the questions that follow
















Explain why in this process the sodium chloride is mixed with calcium chloride.
Why is the anode made of graphite and not steel?
State two properties of sodium metal that make  it possible for it to be collected as shown in the diagram
What is the function of the steel gauze cylinder?
Write ionic equations for the reactions which take  place at:

I Cathode
II Anode
Give one industrial use of sodium metal
Explain why the sodium metal is kept stored under kerosene
The reaction between and methanoic acid at 300 C proceeds according to the information given below
Br2 (aq) + HCOOH (aq) H+ 2Br (aq) + 2H- (aq) + CO2 (g)

Concentration of Br2 (aq) Moldm-3 Time minutes
10.0 x 10-3
8.1 x 10-3
6.6 x 10-3
4.4 x 10-3
3.0 x 10-3
2.0 x 10-3
1.3 x 10-3 0
1
2
4
6
8
10
On the grid below, plot a graph of concentration of Bromine (Vertical axis against time)
From the graph determine:
The concentration of bromine at the end of 3 minutes
The rate of reaction at time ‘t’ where t = 1 ½ minutes
Explain how the concentration of bromine affects the rate of reaction
On the same axis sketch the curve that would be obtained if the reaction was carried out at 200 C and label the curve as curve II. Give a reason for your answer.
(a) The diagram below represents a set up that was used to obtain dry nitrogen from air.
Study it and answer the questions that follow

Name solid Q
What is the purpose of sodium hydroxide?
Write an equation for the reaction which took place in tube P

Give the name of one impurity present in the nitrogen gas obtained

Give a reason why liquid  nitrogen is used  for storage of semen for  artificial insemination
The set up below was used to prepare  nitric acid










Give the name  of liquid R
Write an equation for the reaction which took place in the glass retort
Explain the following

I. Nitric acid is stored in dark bottles
II. The reaction between copper metal with 50% nitric acid (one volume of acid
added to an equal volume of water) in an open test tube gives brown fumes.

A factory uses nitric acid and ammonia gas as the only reactants for the preparation of fertilizer. If the daily production of the fertilizer is 4800 kg calculate the mass of ammonia gas used daily.


(a) In an experiment, dry hydrogen chloride gas was passed through heated  

zinc turnings as shown in the diagram below. The gas produced was then passed through heated lead (II) oxide.

What is the function of water in the flask?

Write equations for the reactions that took place in the tubes
S
V
How would the total mass of tube V and its contents compare before after the experiment? Explain

Chloride can be prepared by  using the following three agents; solid sodium chloride, concentrated sulphuric acid and potassium permanganate

(i) What is the role of each of the following in the reaction?
I Concentrated sulphuric acid
II potassium permanganate
(ii) Name the bleaching agent formed when chlorine gas is passed through cold
dilute sodium hydroxide solution

(iii) Name one other use of the compound formed in (ii) above other than
bleaching
1.9 gm of magnesium chloride was dissolved in distilled water. Silver nitrate solution was added until in excess. Calculate the mass of silver nitrate that was used for the complete reaction. Relative molecular mass of magnesium chloride = 95, N = 14.0, O = 16.0, Ag = 108.0

CHEMISTRY PAPER 233/ 1 K.C.S.E 1998
QUESTIONS
An isotope of Uranium 234U, decays by emission of an alpha particle to thorium
92
Write the equation for the nuclear reaction undergone by isotope.
Explain why it is not safe to store radioactive substances in containers made from aluminium sheets.
Study the information in the table and answer the question below the table.
Substance Solubility g /100g water
A 1.26 x 102
B 1.09 x 102

Describe how a solid sample of substance A could be obtained from a solid mixture of A and B.
Give one advantage and one disadvantage of using petrol containing tetraethyl lead in motor vehicles.
Use the information below to answer the questions that follow:
Zn2+ (aq) + 2e zn(s) -0.76
Al3+ (aq) + 3e Al (s) -1.66
Fe2+ (aq) + 2e Fe(s) -0.44

a). Calculate the E value for the electrochemical cell represented bellow.

Al(s) Al3+ (aq) Fe2+ (ag) Fes(s)

Give a reason why aluminium metal would protect iron from rusting better than zinc metal.      


The table below shows some properties of substances C,D and E.  Study it and answer the questions that follow.

Substance M.P (0C) Solubility in water Electrical solid state Conductivity molten stated.

E -39 Insoluble Good good
D 1610 Insoluble Poor poor
E 801 Soluble Poor good

Select substance
Within a giant molecular structure
That is not likely to be an element

On complete combustion of a sample of hydrocarbon, 3.52 gm of carbon dioxide and 1.44gm of water were formed.  Determine the molecular formula of the hydrocarbon. (Relative molecular masses of hydrocarbon =56, carbon dioxide 44, water = 18 and relative atomic masses H = 1.0 and c=12.0)      
  1. A sample of water drawn from a river passing through an agricultural district was divided into two portions. The first portion gave a white precipitate when acidified barium chloride was added. The second portion when warmed with aqueous sodium hydroxide gave a colourless gas, which turned a moist red litmus paper blue.
    Identify the ions present in the river water.
    Suggest the possible sources of the ions identified in (a) above.
  2. The equation below represents a redox reaction. Identify the reducing agent. Give a
    reason. 2FeCl2 (aq) + Cl2 (g) 2Fe Cl3(aq)
  3. (a) What is meant by dynamic equilibrium?
    (b) State and explain the observation that would be made if a few pellets of potassium hydroxide are added to the equilibrium mixture.
  4. An ion of phosphorous can be represented as 31 P3-
    15
    Draw a diagram to show the distribution of the electrons and the composition of the nucleus of the ion of phosphorous.
  5. Diamond and graphite are allotropes of carbon. In terms of structure and bonding explain
    the following.
    (a) Diamond is used in drilling through hard rocks
    (b) Graphite is used as a lubricant
  6. Distinguished between a strong and a weak acid. Give examples.
  7. The set-up below was used to electrolyze aqueous copper (II) sulphate Explain why the bulb light is brightly at the beginning of the experiment and becomes dim after sometime.
    Write the ionic equation of the reaction that took place.
    Draw the structural formula of:
    Ethanol
    Propanoic
    Give the name of the organic compound formed when ethanol and propanoic acid react in the presence of concentrated sulphuric acid.
  8. The grid below shows part of a periodic table. The letters do not represent the actual
    symbols of the elements Select the:
    element which has the largest atomic radius
    Most reactive non-metal
    Show on the grid the position of the element J which forms J2 ions with electronic configuration 2, 8, 8.
  9. Study the information in the table below and answer the questions below the table.
    Bond Bond energy (kJmol-1)
    C-H
    Cl-Cl
    C-Cl
    H-Cl 414
    244
    326
    431
    Calculate the enthalpy change of the reaction:
    CH4 (g) + Cl2(g) CH3Cl(g) + HCl(g)
  10. The diagram below represents a paper chromatogram for three brands of juices suspected to contain banned food colorings.

The results showed the presence of banned food colorings in L and M only. On the same diagram:
Circle the spots which show the banned food colorings
Shoe solvent front.

  1. Urea, (NH2)2CO is prepared by the reaction between ammonia and carbon dioxide. 2NH3(g) + CO2(g) (NH2)2CO(aq) + H2O(l)
    In one process, 680 kg of ammonia were reacted with excess carbon dioxide.
    Calculate the mass of urea that was formed. (H = 1.0, c+ 12.0, N =14.0, O = 16.0 and relative molecular mass of ammonia = 17)
    Calculate the mass of Urea that was formed Describe how a solid sample of lead (II) Chloride can be prepared using the following reagents, dilute nitric acid, dilute hydrochloric acid and lead carbonate.
    The diagram below represents a charcoal burner. Study it and answer the questions that follow

Write equations for the reactions taking place at I and I and II

The formula given below represents a portion of a polymer Give:






The name of the polymer.
One disadvantage of continued use of this polymer.
The scheme below shows some reaction sequence starting with solid N.










Identify solid N
Write the formula  of the complex ion present in solution
A sealed glass tube containing air at s.t.p was immersed in water at 1000c.  Assuming that there was no increase in the volume of the glass tube due to the expansion of the glass, calculate the pressure of the inside tube.  (standard pressure = 760mmHg,)

A beekeeper found that when stung by a bee, application of a little solution of hydrogen carbonate helped to relieve the irritation from the affected area.  Explain.

The diagram below shows the physical state of matter.  Study it and answer the questions that follow.

Identify the processes R, V, w and U
Name one substance which can undergo the process represented by S and T.
The table below gives the energy required to remove the outermost electron for some group I elements.
Element I II III IV
Energy kJmol-1 494 418 519 376

Arrange the elements in order of their reactivity starting with the most reactive.

A hydrocarbon slowly decolorizes bromine gas in the presence of sunlight but does not decolourise acidified potassium permanganate

Name and draw the structural formula of the fourth member of the series to which the hydrocarbon belongs.
The column below was used do soften hard water

Explain how the hard water was softened as it passed through the column
After some time the material in the column  is not able to soften hard water 
How can the material be activated?
Give one advantage of using hard water for domestic purposes.
  1. What is the oxidation number of chlorine in CO4

CHEMISTRY PAPER 233/2 K.C.S.E – 1998
QUESTIONS

  1. (a). An ore is suspected to contain mainly iron. Describe a method that
    can be used to confirm the presence of iron in the ore
    Excess carbon monoxide gas was passed over a heated sample of an oxide of iron as shown in the diagram below. Study the diagram and the data below it to answer the questions that follow.

Mass of empty dish = 10.98g
Mass of empty dish 4 oxide of iron = 13.30g
Mass of empty dish 4 residue = 12.66g
Determine the formula of the oxide of iron. (relative formula mass of oxide iron = 232, Fe = 56.0 , O = 16.0)
Write an equation for the reaction which took place in the dish
Corrosive is a destructive process in which iron which is converted into hydrated iron (III) oxide
State:
two conditions necessary for rusting to occur
One method used to protect iron from rusting
Explain why it is not advisable to wash vehicles using seawater

  1. (a) The following equations represents two different types of reactions
    (i) nC4H8(g) (C4H8)n(s)
    (ii) C2H6(g) + CI2(g) C2H5CI(I) + HCI(g)
    State the type of reaction represented by:
    (i)
    (ii)
    The fermentation of glucose produces ethanol as shown in the equation below
    C2H12O6(aq) 2CH3CH2OH(aq) + 2CO2(g)
    State how the concentration of ethanol produced could be increased
    State and explain the observation that would be made when a piece of sodium metal is added to a sample of ethanol contained in a beaker
    Give two commercial uses of ethanol other in the manufacture of alcoholic drinks
    The molecular formula of a hydrocarbon is C6H14. The hydrocarbon can be converted into two other hydrocarbons as shown by the equation below
    Name and draw the possible structural formula of X
    Name
    Structural formula
    State and explain the observation that would be made if a few drops of bromide water were added to a sample of X.
    Write an equation for the complete combustion of C3H8
  2. The flow chart below shows the industrial preparation of ammonia and the process used in the manufacture of some ammonium compounds. Study and answer the questions that follow Give the name of the
    Process in step 1
    Reaction that takes place in step 5
    State one other source of hydrogen gas apart from natural gas
    Explain why it necessary to compress nitrogen and hydrogen in this process
    Write an equation for the reaction which takes place in step 6
    Name the catalyst and the reagents used in step 3
    Catalyst
    Reagent
    Name compound Z1
    Give one commercial use of compound Z2
  3. The set – up below was used to prepare anhydrous chlorides of a number of elements in a
    laboratory where no fine cupboard was available. The chlorides were to be collected in flask

The following table shows the melting and boiling points of the chlorides that were prepared.
Explain why it is necessary to pass dry chlorine through the apparatus before heating each element
Give tow reasons why tubes II and III were filled with Soda lime (solid mixture of sodium hydrogen and calcium hydrogen)
Explain why it would not be possible to collect any sodium chloride in flask 1
Name one other substance that can be used in tubes II and III
Write an equation for the reaction that forms phosphorous (III) chloride
Describe how you would separate a mixture of sodium chloride and aluminium chloride
(a) The table below gives the solubilities of hydrated copper (II) sulphate in mol dm3 at different temperatures
(i) On the grid provided, plot a graph of solubility of copper (II) sulphate (vertical
axis) against temperature.
(ii) From the graph, determine the mass of copper (II) sulphate deposited when
solution is cooled from 700 C to 400C.
(Molar mass of hydrated copper (II) sulphate = 250g)
(b) In an experiment to determine the solubility of sodium chloride, 5.0cm3 of a
saturate solution of sodium chloride weighing 5.35g were placed volumetric and diluted to a total volume of 250cm3
25.0cm3 of the dilute solution chloride completely reacted with 24cm3 of 0.1M silver nitrate solution.
AgNO3(aq) + NaCI(aq) AgCl(s) + NaNO3(aq)
Calculate:
(i) Moles of silver nitrate in 24cm3 of solution
(ii) Moles of sodium chloride in 25.0cm3 of sodium
Moles of sodium chloride in 250cm3 of solution
Mass of sodium chloride in 5.0cm3 of saturated sodium chloride
Solution (Na = 23.0, CI = 35.5)
Mass of water in 5.0cm3 of saturated solution of sodium chloride
The solubility of sodium chloride in g/100 water

  1. In order to determine the molar of neutralization of sodium hydroxide, 100cm3 of 1M sodium hydroxide and 100cm3 of 1 M hydrochloric acid both at the same initial temperature were mixed and stirred continuously with a thermometer. The thermometer of the resulting solution was recorded after every 30 seconds until the highest temperature of the solution was attained. Thereafter the temperature of the solution was recorded for a further two minutes
    (i) Why was it necessary to stir the mixture of the two minutes
    (ii) Write an ionic equation for the reaction which took place
    (iii) The sketch below was obtained when the temperature of the mixture
    were plotted against time. Study and answer the questions that follow. What is the significance of point Y2?
    Explain why there is a temperature change between points
    Y1 and Y2
    Y3 and Y4
    (iv) In the initial temperature for both solutions was 24.50C and the highest temperature attained by the mixture was 30.90C
    Calculate the:
    heat change for the reaction
    (specific heat capacity of the solution = 4.2Jg -1K-1 and the density of the solution = 1.0g/cm3
    Molar heat of neutralization of sodium hydroxide
    (v) Explain how the value of the molar heat of neutralization obtained in this experiment would compare with the one that would be obtained if the experiment was repeated using 100cm3 of 1 Methanoic acid instead of hydrochloric acid.
    (b) On the grid provided below, draw an energy level diagram for the reaction
    between hydrochloric acid and sodium hydroxide
  2. Study the information given in the table below and answer the questions that follow. The letters do not represents the actual symbols of the elements
    Element Atomic number Boiling point
    S
    T
    U
    V
    W 3
    13
    16
    18
    19 1603
    2743
    718
    87
    1047
    (a) Select the elements which belong to the same
    (i) Group
    (ii) Period
    (b) Which element
    (i) Is in gaseous state at room temperature? Explain
    (Take room temperature to be 298K)
    (ii) Does not form an oxide?
    (c) Write the
    (i) Formula of the nitrate of element
    (ii) Equation for the reaction between elements S and U
    (d) What type of bond would exists in the compound formed when U and T react?
    Give a reason for your answer
    (e) The aqueous sulphate of element W was electrolyzed using inert electrodes Name
    the products formed at the:
    (i) Cathode
    (ii) Anode

CHEMISTRY PAPER 233/1 K.C.S.E 1999
QUESTIONS
Aluminium metal is a good conductor and is used for overhead cables. State any other two properties that make aluminium suitable for this use
Study the flow chart below and answer the questions that follow

(a) Name:
(i) The reagent used in step I
(ii) Compound A
(b) Write an ionic equation for the reaction is step IV

State and explain the observation that would be made when  a few drops of concentrated sulphuric acid are added to a small sample of hydrated copper (II)  sulphate
4.76g of liquid ammonia and 4.76g of  liquid nitrogen were each allowed warming up and hanging into gas at warm temperature and pressure. Relative atomic  masses: H=1.0 and N=14.0. Using the data given above, explain which gas occupied the greater volume
Sulphur dioxide  and nitrogen dioxide react as shown in the equation below

SO2(g) + NO2(g) → SO3 (g) + NO(g)
Using the oxidation numbers of either sulphur or nitrogen, show that this is a redox reaction
Identify the reducing agent
What type of bond is formed when lithium and Fluorine react? Explain
(Atomic numbers: Li = 3 and F = 9)

Write the formula of sulphide of an element C, whose atomic number is 5. (C is not the actual symbol of the element)

The table below shows the solubility of a salt at various temperatures

Temperature (0C) Solubility g/ 100g Water
0
40
80
110 36
30
25
20

What would happen if a sample of a saturated solution of the salt at 400C is heated to 800C. Explain

State the observation that would be made when a piece of sodium metal  is placed in samples of:

Pentane: _
Pentanol: _

D gm of potassium hydroxide were dissolved in distilled water to make 100cm3 of solution. 50cm3 of the solution- required 50cm3 of 2 M nitric acid for complete neutralization. Calculate the mass D, of potassium hydroxide
(KOH)(aq) + HNO3(aq) →KNO3 (aq) + H2O (I)
Relative formula mass of KOH = 56)
In an attempt to prepare sulphur dioxide gas, dilute sulphuric acid was reacted with barium sulphuric. The yield of sulphur dioxide was found to be negligible explain

The curve below represents the changes in the concentration of substance  E and F with time

In the reaction; E (g) F(g)

Which curve  represents the changes in concentration of substance F? Give a reason
Give a reason for shapes of curves after time ‘t’ minutes

Use the cell representation below to answer the questions that follow

Cr(s) / Cr3+ (aq) //Fe2+ (aq) /Fe(s)
Write the equation for the cell reaction
If the E.M.F of the cell is 0.30 volts and the Eθ value for cr3+aq / Cr (s)
(a) A few drops of freshly prepared iron (II) sulphate solution were added to potassium nitrate solution in a test – tube. Concentrated sulphuric acid was then carefully added to the mixture. State the observation that were made
(b) Write an equation for the reaction that occurs when solid potassium nitrate is strongly heated
2KNO3 →2KNO2 (s) + O2
Use the information below to answer the question that follows
Ca (s) + ½ O2 (g) → CaO(s); ∆H = 635 kjmol-1
C(s) + O2 (g) →CO2(g); →∆H = -394kJmol-1
Ca (s) + C (s) + 3/2 O2 →CaCO3 (s) ; ∆H = -1207 kJ mol-1
Calculate the enthalpy change for the reaction
CaO(s) + Co2 (g) →CaCO3(s)
Under certain conditions, carbon dioxide reacts with water to form methanol (CH3 OH) and oxygen as shown below
2CI2 (g) + 4H2O(I) →2CH3OH(I) + 3O2 (g) : ∆ H = + 1452 Kj
What would be the effect on the yield of methanol if the temperature of the reaction mixture is increased? Explain

In an experiment a certain volume of air was passed from syringe to syringe over heated zinc powder as shown in the diagram below

The experiment was repeated using excess magnesium powder. In which of two experiments was the change in volume of the air greatest. (Give reasons)

Use the information in the table below to answer the questions that follows

Element Fluorine Chlorine Bromine Iodine
Heat of vaporization 3.16 10.2 15.0 22.0
Explain the trend in the molar heats of vaporization

The diagram below shows a set up for the laboratory preparation and collection of dry  chlorine  gas

(a) Name
(i) Substance G
(ii) A suitable drying agent Conc.
(b) What property of chlorine makes it possible for it to be collected as shown in
the diagram?

The set up below was used to investigate some properties of two gases  M and N











a)  Name
        (i)     Substance G
        (ii)    A suitable drying agent conc.

b) What property of chlorine makes it possible for it to be collected as shown in the diagram?
The set up below was used to investigate some properties of two gases M and N

When beaker A was filed with gas M, the level of water in the glass tube rose to
point II. When the experiment was repeated using gas N, the level of water dropped to point III. Explain these observations.

State  and explain  one disadvantages of using  hard water  in boilers

Compound  L reacts with hydrogen  bromide gas to give another  compound whose structure is

H H H Br H
I I I I I
H – C – C – C – C – C – H
I I I I I
H H H H H
(a) Give the structural formula and name of compound L
(b) Write an equation for the reaction, which takes place between ethane and
excess chlorine gas
When excess carbon monoxide gas was passed over heated lead (II) oxide in combustion tube, lead (II) oxide was reduced
Write an equation for the reaction, which took place
What observation was made in the combustion tube when the reaction was complete?
Name another gas, which could be used to reduce lead (II) oxide
One of the fuels associated with crude oil is natural gas. Name the main constituent of natural gas and write an equation for its complete combustion
Name:
Equation:
When solid magnesium carbonate was added to a solution of hydrogen chloride in methylbenzene, there was no apparent reaction. On addition of water to the resulting mixture, there was vigorous effervescence. Explain these observations
The graph below shows the mass of a radioactive isotope plotted against time

Using the graph, determine the half – life of the isotope
Calculate the mass of the isotope present after 32 days
The table below shows the PH  values of solutions I, II, III and IV.

Solution I II III IV
PH 2 7 11 14

which solution is likely to be that of calcium hydroxide?
Select the solution in which a sample of aluminium oxide is likely to dissolve. Give reason for your answer
Bromine reacts with ethane as shown below

C2H6 + Br →C2H5Br + HBr

What condition is necessary for this reaction to occur?
Identify the bonds which are broken and those that are formed  

Bonds broken
Bonds formed

CHEMISTRY PAPER 233/2 K.C.S.E 1999
QUESTIONS
The table below gives the volume of the gas provided when different volumes of 2M hydrochloric were reacted with 0.6g of magnesium powder at room temperature

Volume of 2M hydrochloric acid (cm3) Volume of gas (cm3)
0
10
20
30
40
50 0
240
480
600
600
600

Write an equation fro the reaction between magnesium and hydrochloric acid
On the grid provided plot a graph of the volume of gas produced
(vertical axis), against the volume of acid added (Note the reaction comes to completion, the volume of the gas produced directly proportional to completion, the acid added).
From the graph determine

c) i) The volume for the gas produced if 12.5cm3 of 2M hydrochloric acid had been used.
ii) The volume of 2M hydrochloric acid which when reacted completely with 0.6 of magnesium powder.
e) Given that one mole of the gas occupied 24000cm3 at room temperature.

Calculate the relative atomic mass of magnesium.
The set – up below was used during the electrolysis of aqueous magnesium sulphate using inert electrodes.

name a suitable pair of electrodes for this experiment
Identify the ions and cations in the solution
On the diagram label the cathode
Write ionic equations for the reactions that took place at the anode.
Explain the change that occurred to the concentration of magnesium sulphate solution during the experience.
During the electolysis a current of 2 amperes was passed through the solution for 4 hours. Calculate the volume of the gas produced at the anode.(1 faraday 96500 coulombs and volume of a gas at room temperature is 24000cm3)
One of the uses of electrolysis is electroplating

What is meant by electroplating?
Give tow reasons why electroplating is necessary.
Study the information in the table below and answer the questions that follow. The letters do not represent the symbols of the elements.
Element(C) Atomic number Melting point
L
M
N
Q
R 11
13
14
17
19 97.8
660
1440
401
63.7
a) Write the electrons arrangement for the atom formed by elements and M and Q
b) Select an element which is
i) The most reactive non – metal
ii) A poor conductor of electricity
c) In which period of the periodic table does elements R below.
d) Element R lodes its outermost electron more readily than I. Explain
e) Using dots(.) and crosses (x) to represent outermost electrons show
bonding in the compound formed elements N and Q.
f) Explain why the melting point elements M is higher than that of element .
g) Describe how a solid mixture of sulphate of R and lead sulphate can be separated into solid samples.

  1. a) The flow chart below shows a sequence of reactions starting with.
    Study and answer the questions that follow.

i) Name the reagent and state the condition for the reaction in step.
Reagent
Condition
ii) Give the names of the following
Solid S
Solid V
Solid T
iii) Give reasons for the colour change in step 2
Write an ionic equation for the reaction which takes place in step 3.
v) Name one other substance that could be used instead of sodium hydroxide in step III.
b) In an experiment 3.36g of iron fillings were added to excess aqueous copper(II) sulphate. Calculate the mass of copper that was deposited.
Cu = 63.5, Fe = 56.0
5 a) When an organic compound Y is reacted with aqueous sodium carbonate, it produces carbon dioxide reacts with propanol to form a sweet smelling compound Z whose formula is.
O

CH3 CH2   C    -    O    -  CH2 CH2 CH3

Name and draw the structural formula of compound Y.
What is the name of the group of compounds to which Z belongs?

b) In an experiment excess ethanol was warmed with potassium dichromate for about twenty minutes. State and explain the observation that was made at the end of the experiment.
c) The scheme below was used to prepare a cleaning agent.
Study and answer the questions that follow.

What name is given to the type of cleaning agent prepared by the method shown in the scheme?
Name one chemical substance added in step II
What is the purpose of adding the elements substance names in C(ii) above.
Explain how an aqueous solution of the cleansing removes oil from utensils during washing.
  1. a) The diagram below shows a set –up used by as a student in an attempt to prepare
    and collect oxygen gas. Complete the diagram correcting the mistakes on it
    Identify solid W.
    A piece of phosphorus was burnt in excess and the product obtained was shaken with a small amount of hot water to make a solution.
    Write an equation for the burning of phosphorus in excess air.
    Explain why cooking pots made of aluminium do not corrode when exposed to air.
    The reaction between sulphur dioxide and oxygen to form trioxide in the contact process in exothermic.
    2So(aq) + O2(g)  2SO3(g)
    Factory manufacturing sulphuric acid by contact process produces 350kg of sulphur trioxide per day (conditions) for the reaction catalyst. 2 atmospheres pressure and temperatures between.
    (400 – 500 oC)
    i) What is meant by an exothermic reaction?
    ii) How would the yield per day of sulphur trioxide be affected
    Temperatures lower than 4000oC are used? Explain.

CHEMISTRY PAPER 233/1 K.C.S.E 2000
QUESTIONS

  1. Explain the change in mass that occurs when the following substances are separately heated in open crucibles
    (a) Copper metal
    (b) Copper (II) nitrate
  2. The equation below represents a redox reaction
    Mg (s) + 2HCI (aq) → MgCI2 (aq) + H2
    Write down the equation for the reduction process
    Which substance is oxidized
  3. The simplified flow chart shows some of the steps in the manufacture of sodium carbonate by the Solvay process

(a) Identify substance L
(b) Name the process – taking place in step II
(c) Write an equation for the reaction, which takes place in step III

  1. When a current of 1.5 amperes was passed though a cell containing m3+ ions of a metal
    M for 15 minutes, the mass of the cathode increased by 0.26g.
    (1 Faraday = 96500 coulombs)
    (a) Calculate the quantity of electricity used
    (b) Determine the relative atomic mass of metal M
  2. The information below relates to elements S,T,U and X. ( the letters do not represents the actual symbols of the elements.
    (i) T displaces X from an aqueous solution containing ions of X
    (ii) Hydrogen gas reduces heated oxide of S but does not reduce the heated oxide of X
    (iii) U liberates hydrogen gas from cold water but T does not
    (a) Write an equation for the reaction between T and the ions of X.
    Both T and X are in group II of the periodic Table)
    (b) Arrange the elements in order of their increasing reactivity
  3. Starting with copper metal, describe how a solid samples of copper (II) carbonate can be prepared.
  4. Give two reasons why helium is used in weather balloons
  5. Study the solubility curves below and answer the questions that follows

What happens when a solution containing 40gm of potassium chlorate and 40gm of potassium nitrate in 100gm of water at 900C is cooled to 400C? Explain

  1. A hydrocarbon P was found to decolourise bromine water. On complete combustion of 2 moles of P, 6 moles of carbon dioxide and 6 moles of water were formed
    (a) Write the structural formula of P
    (b) Give the name of P
    (c) Name one industrial source of P
  2. Use the scheme below to answer the questions that follow

(a) Identify the solid
H
J
(b) State one commercial use of solid J

  1. 20.0cm3 of a solution containing 4 gm per litre of sodium hydroxide was neutralized
    by 8.0cm3 of dilute sulphuric acid. Calculate the concentration of sulphuric acid in
    moles per litre (Na = 23.0, O = 16.0, H = 1.0)
  2. A student set up the apparatus shown below to prepare ammonia gas and react it with
    copper (II) sulphate solution.

(a) Identify solution V
(b) State the observations which were made in the beaker

  1. A radioactive isotope X2 decays by emitting two alpha (a) particles and one beta (β) to
    from 214 Bi
    83
    (a) What is the atomic number of X2?
    (b) After 112 days, 1/16 of the mass of X2 remained. Determine the half life of X2
  2. The table below shows the tests carried out on separate samples of water drawn from a
    well and the results obtained
    Tests Results
    (i) Addition of excess aqueous
    (ii) Addition of a few drops of dilute sulphuric acid
    (iii) Addition of dilute hydrochloric acid followed by few drops of Barium chloride

(a) Identify the cation and the anion present in the water
Cation
Anion
(b) Write an ionic equation for the reaction which takes place in test (iii)

  1. State any two differences between luminous and non – luminous flames
  2. Compound Q is a solid with a giant ionic structure. In what form would the compound conduct an electric current
  3. Study the set- up below and answer the questions that follow

(a) Write an equation for the reaction, which take place in the combustion tube
(b) What property of gas Z allows it to be collected as shown in the diagram

  1. A given volume of ozone, (O3) diffused from a certain apparatus in 96 seconds.
    Calculate the time taken by an equal volume of carbon dioxide (CO2) to diffuse under the same conditions (O = 16.0, C = 12.0)
  2. The curves below were obtained when two equal volumes of hydrogen peroxide of the
    same concentration were allowed to decompose separately. In one case, manganese (IV) oxide was added to the hydrogen peroxide

Which curve represents the decomposition of hydrogen peroxide with manganese (IV) oxide? Explain

  1. Pentane and ethanol are miscible. Describe how water could be used to separate a mixture of pentane and ethanol
  2. Name another gas, which is used together with oxygen in welding
  3. Study the information in the table below and answer the questions that follow. The letters do not represent the actual symbols of the elements)

Element Electrical conductivity Ductility Action of water
A
B
C Good
Good
Good Good
Poor
Good No reaction
No reaction
Reacts
Select an element which
(a) Is likely to be sued in group II of the periodic table
(b) Could be used to make electric cables
(c) Likely to be graphite

  1. When a solid sample of sulphur is heated in a test tube, it changes into a liquid,
    which flows easily. On further heating, the liquid darkness and does not flow easily. Explain these observations.
  2. Hydrogen and fluorine react according to the equation below
    H2 (g) + F2 (g) 2HF (g) ; ∆H = – 538kJ
    (a) On the grid provide below, sketch the energy level diagram for the forward reaction
    (b) Calculate the molar enthalpy of formation of HF
  3. Explain why it is not advisable to leave a Jiko with burning charcoal in a closed
    room where one is sleeping.
  4. In an experiment, ammonia chloride was heated in a test tube. A moist red litmus
    paper placed at the mouth of the test tube first changed blue then red. Explain these
    observations
  5. State and explain the function of tartaric acid in baking powder

CHEMISTRY PAPER 232/2 K.C.S.E 2000
QUESTIONS
(a) The grid given below represents part of the periodic table. Study it and answer the questions that follow. (the letters do not represents the actual symbol of the elements)

(i) What name is given to the group of elements to which C and F belong?
(ii) Which letter represents the element that is the least reactive?
(iii) What type of bond is formed when B and E react? Explain
(iv) Write the formula of the compound formed when element D and oxygen gas react
(v) On the grid, indicate with a tick the position of element G which is in the third
grid, indicate with a tick the position of element G which is in the third period of the periodic table and forms G3- ions

(b) Study the information in the table below and answer the questions that follow ( the letters do not represent the actual symbol of the substances)

Substance Melting Point (0C) Boiling Point (0C) Solubility in water Density at room temperature g/cm3
H
J
K
L -117
-78
-23
-219 78.5
-33
77
-183 Very soluble
Very soluble
Insoluble
Slightly soluble 0.8
0.77 x 10-3
1.6
1.33 x 10-3

(i) Which substance would dissolve in water and could be separated from the solution by fractional distillation? Give a reason
(ii) Which substances is a liquid at room temperature and when mixed with water two layers would be formed?
(iii) Which letter represents a substance that is gas at room temperature and which can be collected:
I. Over water? Explain
II. By downward displacement of air? (Density of air is 1.29 x 10-3g/cm3 at room temperature.

(a)     The diagram below represents a mercury cell that can be used in the industrial    manufacture of sodium hydroxide. Study it and  answer the question that follow

(i) Name
I. the raw material introduced at 2
II. Another substance that can be used in the cell instead of graphite
(ii) Identify the by – product that comes out at I
(iii) Give
I. One use of sodium hydroxide
II. Two reasons why mercury is recycled
(b) A current of 100 amperes was passed through the cell of five ( 5) hours
(i) Write the equation for: The reaction that occurred at the mercury cathode
(ii) Calculate the mass of sodium hydroxide that was produced
(Na = 23.0, O = 16.0, H = 1.0, 1 Faraday = 96500 Coulombs)
The flow chart below illustrate the industrial extraction of lead metal. Study it and answer the questions that follow.

(a) (i)     Name the ore that is commonly used in this process
     (ii)   Explain what takes place in the roasting furnace
     (iii)  Identify gas P
     (iv)   Write the equation for the main reaction that takes place in the smelting 
                     Furnace
     (v)    What is the purpose of adding iron in the smelting furnace?
     (vi)   Give two environmental hazards likely to be associated with extraction of 
                    Lead
(b) Explain why hard water flowing in lead pipes may be safer for drinking 
                     than soft water flowing in the same pipes
(c)     State one use of lead  other than the making of lead pipes
  1. (a) (i) In the space provided sketch a labeled diagram to show how hydrogen
    chloride gas can be prepared and collected in the laboratory using sodium
    Chloride and concentrated sulphuric acid ( the gas need not be dry)
    (ii) Write an equation for the reaction that takes place
    (iii) Name one drying agent for hydrogen chloride
    (vi) State and explain the observation that would be made when hydrogen
    chloride gas is bubbled through a solution of lead (II) nitrate
    (v) Concentrated hydrochloric acid is used for removing oxide from metal surfaces ( picking). Explain why concentration nitric acid cannot be used for the purpose.
    (b) A sample of hydrogen chloride gas was dissolved in water to make 250cm3 of solution required 46 cm3 of 11.0M Sodium hydroxide for complete neutralization.
    (i) Calculate the number of moles of hydrochloric acid in 25cm3 of solution
    (ii) Determine the mass of hydrogen chloride that was dissolve to make 250cm3 of solution (Cl = 35.5, H=1.0)
  2. (a) Give the names of the following compounds
    (i) CH3CH = CHCH2CH3
    O

    (ii) CH3CH2CH2C – OH
    (b) Ethane and Ethene react with bromine according to the equation given below
    (i) C2H6(g) + Br2(g) C2H5Br2(g) + HBr(g) (ii) C2H4(g) + Br2(g) C2H4Br2(I) Name the type of bromination reaction that takes place in: (i) and (ii) (i) Write the equation for the combustion of butane
    (ii) The pH of substances K was found to be less than 7. Explain this observations

(d) The polymerization of tetra flouroathene (C2H4) is similar to that of ethane
( C2H4)
(i) What is meant by the term polymerization?
(ii) Draw the structural formula of a portion of the polymer obtained from the monomer C2H4
(e) State any two advantages that synthetic polymers have over natural polymers

  1. (a) The following diagrams show the structures of two allotropes of carbon. Study them and answer the questions that follow

(i) Name allotrope
M
N
(ii) Give one use of N
(iii) Which allotrope conducts electricity? Explain

(b) In an experiment, carbon dioxide gas as passed over heated charcoal and the gas produced collected as shown in the diagram below

(i) Write an equation for the reaction that took place in the combustion tube
(ii) Name another substance that can be used instead of sodium hydroxide
(iii) Describe a sample chemical test that can be used to distinguish between carbon dioxide and carbon monoxide
(iv) Give one use of carbon monoxide
7 (a) A student was supplied with a colourless liquid suspected to be water
(i) Describe one chemical test that could have been used to show that the liquid was water
(ii) How could it have been shown that the liquid was pure water?
(b) The flow chart below shows the various stages of water treatment. Study it and answer the questions that follow

(i) Which substances are likely to be removed in filtration unit I?
(ii) What is the name of the process Y?
(iii) What is the purpose?
I Process Y
II Addition of sodium hypochlorite
(c) It was confirmed that magnesium sulphate was present in the tap water
(i) What type of hardness was present in the water?
(ii) Explain how the hardness can be removed

CHEMISTRY PAPER 233/1 K.C.S.E 2001
QUESTIONS

  1. Study the nuclear reaction given below and answer the questions that follow.

(a) 12 and 14 are isotopes. What does the term isotopes. What does the term isotope mean?
C C
6 6
(b) Write an equation for the nuclear reaction in step II
14 14 0 or 14 14 0
C N e C N e
6 7 I 6 7 i
(c) Give one use of 14C
6

  1. In an experiment, 0.8gm of magnesium of powder were reacted with excess dilute sulphuric acid at 250C . The time for the reaction to come to completion was recorded.
    The experiment was repeated at 400C. In which experiment was the time taken shorter? Explain your answer.
  2. The electronic structures for elements represented by letters A,B,C,D are
    A=2 .8.6 B 2.8.2 C 2. 8. 1 D 2. 8. 8.
    a) Select the element which forms:
    (i) a double charged cation
    (ii) A soluble carbonate
    b) Which element has the shortest atomic radius?
  3. Study the scheme below and answer the questions that follow. a) Identify solid E.
    b) Write an ionic equation for the reaction in step II that produces solid F.
  4. Give a reason why phosphorus is stored under water.
  5. At 298K and 1 atmosphere, graphite changes into diamond according to the equation:
    C (graphite) C(diamond); =2.9 kJmo-1
    In the space provided, sketch a simple energy level diagram for the above change.
  6. How would you obtain a sample of pure iodine from a mixture of iodine and lead sulphate?
  7. 10gm of sodium hydrogen carbonate were dissolved in 20cm3 of water in a boiling tube. Lemon juice was then added drop wise with shaking until there was no further observable change.
    a) Explain the observation, which was made in the boiling tube when the reaction was in progress
    b) What observation would have been made if the lemon juice had been added to copper turnings in a boiling tube? Give reason?
  8. Sample solutions of salt were labeled as I,II, III and IV. The actual solutions, not in that order are lead nitrate, zinc sulphate potassium chloride and calcium chloride.
    a) When aqueous sodium carbonate was added to each sample separately, a white precipitate was formed in I, III and IV only. Identify solution II.
    b) When excess sodium hydroxide was added to each sample separately, a white precipitate was formed in solutions III and I only.
    Identify solution I
  9. A weighed sample of crystalline sodium carbonate (Na2CO3. H2O) was heated in a crucible until there was no further change in mass.
    Calculate the number of moles (n) of the water of crystallization
  10. A certain matchstick head contains potassium chlorate and sulphure.
    On striking the two substances react to produce sulphure dioxide and potassium chloride. Explain the environmental effect of using such matches in large numbers.
  11. Describe a simple laboratory experiment that can be sued to distinguish between sodium and sulphide and sodium carbonate.
  12. The information in the table below relates to elements in the same group of the periodic table. Study it and answer the question that follows:
    Element Atomic size
    G1
    G2
    G3 0.19
    0.23
    0.15

Which element has the highest ionization energy? Give reason.

  1. When the oxide of element H was heated with powdered carbon the mixture glowed and carbon dioxide was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction.
    a) Suggest one method that can be used to extract element J from its oxide
    b) Arrange the elements H, J and carbon in the order of their decreasing creactivity.
  2. When a sample of concentrated sulphuric acid was left in an open beaker in a room for two days, the volume was found to have increased slightly
    a) What property of concentrated sulphuric acid was left in an open beaker in a room for two days, the volume was found to have increased slightly.
    b) State one use of concentrated sulphuric acid that depends on the property named above.
  3. The diagram below shows an iron bar, which supports a bridge. The Iron bar is connected to a piece of magnesium metal.

Explain why it is necessary to connect the piece of magnesium metal to the iron bar.

  1. a) State one cause of temporary hardness in water.
    b) How does distillation remove hardness from water?
  2. In the presence of U.V light, ethane gas undergoes substitution reaction with chlorine.
    (a) What is meant by the term?
    Substitution reaction:
    (b) Give the structural formula and the name of the organic product formed when equal volumes of ethane and chlorine react together.
  3. Explain why burning magnesium continues to burn a gas was bubbled
  4. a)what observation would be made if hydrogen sulphide gas was bubbled through a solution of zinc nitrate?
    b) write an equation for the reaction that takes place in (a) above
    Zn (NO3)2 (aq) + H2S (g) ZnS + 2 HNO3 (aq)
  5. The apparatus shown below shown below was used to investigate the effect of carbon monoxide on copper (II)oxide.

a) State the observation that was made in the combustion tube at the end of the experiment.
b) Write an equation for the reaction that took place in the combustion tube
C) Why is it necessary to burn the gas coming out of tube K?

  1. Explain why hydrogen forms compounds in which its oxidation state is either + 1 or -1 (Atomic number of hydrogen is 1)
  2. The table below shows the properties of substances K,L,M and N

Substances Reaction with oxygen at 25oC Melting point Conductivity
Solid Molten
K
L
M
N Uncreative
Reactive
Uncreative
Uncreative Low

High
Low Poor

Good
Good Good

Good
Good

Select the substances which are likely to be:
a) Copper metal
b) Magnesium chloride

  1. An element P has a relative atomic mass of 88. When a current of 0.5 amperes was passed through the fused chloride of P for 32 minutes and 10 seconds, 0.44g of P were deposited at the cathode. Determine the charge on an ion of P. (1 faraday = 96500 Coulombs).
  2. The melting point of phosphorous dichloride is – 91oC. While that of magnesium chloride is 715oC.In terms of structure and bonding, explain the difference in their melting points.
  3. The Ph of a sample of soil was found to be 5.0.An agricultural office recommended the addition of calcium oxide in the soil. State two functions of the calcium oxide in the soil.
  4. Hydrogen peroxide decomposes according to the equation below:
    H2O2(l) H2O(l) + ½ O2(g) ; H = – 98kJ
    8.5 gm of hydrogen peroxide contained in 100cm3 of solution with water were completely decomposed. Determine the rise in temperature due to the reaction. Specific density of water = 1g/cm3 O =16, H = 1,).

CHEMISTRY PAPER 233/2 K.C.S.E 2001
QUESTIONS

  1. In an experiment to study the rate for reaction between duralumin (an alloy of aluminium, magnesium and copper) and hydrochloric acid, 0.5g of the alloy were reacted with excess 4M hydrochloric acid. The data in the table below was recoded.
    Use it to answer the questions that follow.
    Time (minutes) Total volume of gas (cm3)
    1
    2
    3
    4
    5
    6
    7 0
    220
    410
    540
    620
    640
    640

a) i) On the grid provided, plot a graph of total volume of gas produced (vertical axis)
again time.
ii) From the graph, determine the volume of gas produced at the end of 2 ½ minutes.
b) Determine the rate of reaction between the 3rd and 4th minute.
c) Give a reason why some solid remained at the end of the experiment
d) Given that 2.5cm3 of the total volume of the gas was from the reaction between magnesium and aqueous hydrochloric acid, calculate the percentage mass of aluminium present in 0.5g of the alloy.
(Al = 27.0 and Molar gas volume = 24,000cm3 at 298k)
e) State two properties of duralumin that make it more suitable than aluminium in aeroplane construction.

  1. a) In which homologous series do the following compounds belong
    i) CH3CC
    ii) CH3CH2COO
    b) Raw rubber is heated with sulphur in the manufacture of natural rubber.
    i) What is the name given to the process
    ii) Why is the process necessary? c) Study the scheme given below and answer the questions that follow.

i) Write an equation for the reaction between propane – 1 – 0 / and potassium metal.
ii) Name processes I and II
I
II
iii) Identify the products A and B
iv) Name one catalyst used in process II
v) Draw the structural formular of the repeating unit in the polymer C.
d) State two industrial uses of methane.

  1. a) Study the standard electrode potentials do the half – cells given below and
    answer the questions that follow.(The letters do nor represent the actual symbols of the elements.)
    Eovolts
    N+ aq + e- N(s); -2.92 J+(aq) + e- J(s); +0.52 K+ (aq) + e- ½ K2(g) 0.00 ½ G2(g) + e- G(aq); +1.36 M2+ (aq) + 2e- M(s); -0.44 i) Identify the strongest oxidizing agent. Give a reason for your answer.
    ii) Which two half – cells would produce the highest potential difference when
    combined?
    iii) Explain whether the reaction represented below can take place.
    2N+(aq) + M(s) 2N(s)+ M2+(aq)
    b) 100cm3 of 2M sulphuric acid was electrolysed using the set – up represented by the diagram below. i) Write an equation for the reaction that produces gas L.
    ii) Describe how gas K can be identified
    iii) Explain the difference in :
    I The volume of the gases produced at the electrodes.
    II Brightness of the bulb if 100cm3 of 2M ethanoic acid was
    used in place of sulphuric acid.
  2. a) Fraction distillation of liquid air usually produces nitrogen and
    oxygen as the major products.
    i) Name one substance that is used to remove carbon dioxide from the air
    before it is changed into liquid.
    ii) Describe how nitrogen gas is obtained from the liquid air.
    (Boiling points nitrogen = – 196oC, oxygen = -183oC b) Study the flow chart below and answer the questions that follow.

i) Name element M.
ii) Why is it necessary to use excess air in step 4?
iii) Identify gas Q.
iv) Write an equation for the reaction in step 7
v) Give one use of ammonia nitrate.
c) State and explain the observations that would be made if a sampler of
sulphur is heated with concentrated nitric acid.

  1. a) Give the name of reagent which when reacted with concentrated
    hydrochloric acid produce chlorine gas.
    b) A student out to prepare iron III chloride using the apparatus
    shown in the diagram below.

i) Explain why:
I. It is necessary to pass chlorine gas through the apparatus
before heating begins.
II Calcium oxide would be preferred to calcium chloride in the guard tube.
ii) What property of iron (III) chloride makes it possible to be collected as shown in the diagram?
iii) Write an equation form one chemical reaction that took place in the guard tube.
iv) The total mass of iron (III) chloride formed was found to be 0.5g.
Calculate the volume of chlorine gas the reacted with iron.
(Fe – = 56.0,Cl = 35.5 and Molar gas volume at 298K is 24,000cm3
C) When hydrogen sulphide gas was passed through a solution of iron (III)
chloride, the following observation were made:
i) The colour of the solution changed from reddish – brown to green
and (ii) a yellow solid was deposit .Explain these observations.
d) State and explain the observations that would be made if a moist blue
litmus paper was placed in a gas jar full of chloride gas.

  1. a) Study the information in the table below and answer the questions that follow.
    (The letters do not represent the actual symbols of the elements).

Ionisation Element Electronic configuration Energy Kj mol-1
P
Q
R 2.1
2.8.1
2.8.8.1 519
494
418
i) What is the general name to the group in which elements P,Q and R belong?
ii) What is meant by ionization energy?
iii) Explain why elements has the highest ionization energy.
iv) When a piece of element Q is placed on water. It melts and a hissing
sound is produced as it moves on the surface of the water.
v) Write an equation for the reaction between element Q and water.
b) Distinguish between a strong and a weak base. Give an example of each
c) Neutralization is one of the methods of preparing salts.
i) What is meant by neutralization?
ii) Describe how you would prepare crystals of sodium nitrate starting
with 200cm3 of 2M sodium hydroxide.
iii) Write an equation for the reaction that takes place when a solid
sample of sodium nitrate is heated.

CHEMISTRY PAPER 233/1 K.C.S.E 2002
QUESTIONS
Name One property of neon that makes it possible to be used in electric lamps
Oxygen and sulphur belong to group (VI) of the periodic table. Explain why there is a big difference their (melting points of oxygen is – 2160C while that of sulphur is 440C.
The oxides of elements A and B have the properties shown in the table below. (the letter do not represent the actual symbols of elements)
A B
Gaseous at room temperature Solid at room temperature
Dissolves in water to form an acidic solution Dissolves in water to form an alkaline solution
Give one example of elements A and B
A
B
The following two tests were carried out on chlorine water contained in two test tubes
A piece of blue flower was dropped into the first – tube. Explain why the flower was bleached
The second test- tube was corked and exposed to sunlight after a few days, it was found to contain a gas that rekindled a glowing splint. Write an equation for the reaction which produced the gas

 (a) Write the electronic configuration of calcium ( atomic number  20 ) and beryllium

(atomic number 4)
(b) Why is calcium more reactive than beryllium

When potassium nitrate is heated, it produces potassium nitrate and gas C1¬

(a) Identify gas C
(b) Name the type of reaction undergone by the potassium nitrate
State and explain how the rate of reaction between zinc granules and steam can be increased
The apparatus shown below was set to prepare and collect hydrogen sulphide

(a)     Name solid C2
(b)     Give a reason why warm water is used
(c)     What observation would be made if hydrogen sulphide gas  was bubbled into a 

solution of lead II nitrate?
Use the reactions given below to answer the questions that follow. The letters do not represent the actual symbols of the elements
D(s) + E2+ (aq) →D2+(aq) + E(s)
D (s) + 2F+(aq) → D2+(aq) + 2F(s)
E (s) + 2 F+ (aq) →E2+ (aq) + 2F(s)
G (s) + →E2+(aq) →G2+(aq) + E(s)
G (s) + D2+ (aq) →no reaction
(a) What name is given to the type of reaction given above?
(b) Arrange the elements D, E, F and G in the order of their reactivity starting with the most reactive
(c) Complete the equation below
G(s) + 2F+ (aq) →

The graph below represents a radioactive decay series for isotope H.

Study it and answer the questions that follow

(a) Name the type of radiation emitted when isotope H changes to isotope J.
(b) Write an equation for the nuclear reaction that occur when isotope J changes to isotope K
210 210
J k e
81 → 82 + -1

Identify a pair of isotope of an element in the decay series

In an experiment, sulphur dioxide gas was bubbled into water followed by chlorine gas. The resulting clear solution gave a white precipitate when mixed with a acidified barium chloride solution. Explain these  observations

Concentrated sulphuric acid was added to iron II sulphate acidified with sulphuric acid and the mixture heated. The solution turned from pale green to yellow with evolution of brown gas. Explain these observations.
Use the equations  below to answer the questions that  follow

K(g) + Cl – (g) → KCl (s); ∆ H1 = – 701kJmol-1
KCl (s) →K+(aq) Cl ; ∆H2 = + 15kJmol-1
(a) What is the name of ∆H1?
(b) Calculate the heat change for the process
K(g)+ + Cl- (g) → K+ (aq) + Cl-(aq)
Iron is extracted from its ore by the blast furnace process
(a) Name one ore from which iron is extracted
(b) One of the impurities in iron is removed in the form of calcium silicate. Write an equation for the reaction in which calcium silicate is produced

When carbon dioxide gas was passed through aqueous calcium hydroxide  a white  suspension was formed

(a) Write an equation for the reaction that took place
(b) State and explain the changes that would occur when carbon dioxide gas is bubbled through the white suspension

With  reference to iodine, distinguish between covalent bonds  and Van Der Waals forces
The structures  below represents  a portion of a polymer

(a) Give the name of the polymer
(b) Give one industrial use of the polymer
Describe how a solid sample of Zin (II) carbonate can be prepared starting with zinc oxide
Bismuth chloride (BiCl3) reacts with water according to the equation given below
BiCl3 (aq) + H2O (l) BiOCl (s) + 2 HCl (aq)

(a) State what would happen when a few drops of dilute hydrochloric acid are added to the mixture at equilibrium
(b) Give a reason for your answer in (a) above
The table below gives some information about the electrical conductivity and the likely bonding in substances N,P and Q. Complete the table by inserting the missing information the spaces numbered I, II and III
Substance Likely type of bonding present Electrical solid Conductivity
N Metallic I………………… Conducts
P II……………………. Does not conduct Conducts
Q III …………………… Does not conduct Does not conduct

In an experiment 30cm3 of 0.1 M sulphuric acid were  reacted with  30cm3 of  0.1 M sodium hydroxide
Write  in equation of the reaction that took  place
State the observations that were made  when both  and red litmus papers were  dropped  into the  mixture
Give a reason for your answer  in (a) above
The diagram  below  is set – up for the  laboratory  preparation of oxygen gas

(a) Name solid R
(b) Write an equation for the reaction that takes place in the flask
(c) Give one commercial use of oxygen
When excess lead nitrate solution was added to a solution containing sodium chloride, the precipitate formed was found to weigh 5.56 g. Determine the amount of sodium chloride in the solution ( Pb = 207, Cl = 35.5 Na = 23)
Pb (XO3(aq) + 2NaCl (aq) PbCI2 + NaNO3 (aq) (l)
(a) Give a reason why concentrated sulphuric acid is not used to dry ammonia gas
(b) Name one suitable drying agent for ammonia gas

But -2- ene undergoes  hydrogenation according to the equation given below

CH3CH = CHCH3 (g) + H2 (g) →CH3CH2CH2CH3 (g)

(a) Name the product formed when but -2 – ene reacts with hydrogen gas
(b) State one industrial use of hydrogenation

The set – up below was used to electroplate a metallic spoon. Study  it and answer the questions that follow










(a) Write an ionic equation for the reaction that occurred at the cathode
(b) State and explain what happened to the anode

The following tests were carried out on three separate  portions of a  colourless solution S

Tests Observations
(i) Addition of dilute hydrochloric acid to the
first portion of solution No observable change
(ii) addition of aqueous sodium carbonate to the second portion of solution S A white precipitate was formed
(iii) Addition of aqueous ammonia to the third portion of a solution A white precipitate was formed which dissolved on addition of excess aqueous ammonia
(a) From the information in test (i), name a cation, which is not present in solution S.
(b) Identify a cation, which is likely to be present in solution S
(c) Write an ionic equation for the reaction, which takes place in test (ii)

CHEMISTRY PAPER 233/2 K.C.S.E 2002
QUESTIONS

  1. (a) what method can be used to separate a mixture of ethanol and propanol?
    (b) (i) Explain how a solid mixture of sulphur and sodium chloride can be separated
    Into solid sulphur and solid chloride
    (c) The table below gives the solubilities of potassium bromide and potassium sulphate at O0C and 400C

Substance Solubility g/100g water at
00C 400C
Potassium bromide 55 75
Potassium sulphate 10 12

When an aqueous mixture containing 60g of potassium and 7 g of potassium sulphate in 10g of water at 800C was cooled to 00C some crystals were formed
(i) Identify the crystals
(ii) Determine the mass of the crystals formed
(iii) Name the method used to obtain the crystals
(iv) Suggest one industrial application of the method named in (iii) above

  1. Study the flow chart below and answer the questions follow

(a) Identify substance
(i) A
(ii) B
(b) Name process C
(c) Give one use of PVC
(d) Write an equation for the reaction in which chlorine gas is produced
(e) State and explain the observation that would be made if chlorine gas was bubbled into an
aqueous solution of sodium iodide
(f) In the preparation of a bleaching agent (Sodium hypochlorite), Excess chlorine gas was
bubbled into 15 litres of cold 2 m sodium hydroxide
(i) Write an equation for the reaction between chlorine gas and cold dilute sodium
Hydroxide
(ii) Calculate the:
Number of moles of sodium hydroxide used
Mass in kilograms of the sodium hypochlorite produced = 1. 1175

  1. (a) Distinguish between exothermic and endothermic reaction ( 2mks)
    (b) Changes of state are either exothermic or endothermic
    Name a change of state that is:
    (i) Endothermic ( 1 mk)
    (ii) Exothermic ( 1 mk)

(c) When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the
water does not rise beyond 1000C. Even with continued heated. Explain this observation.

(d) Study the energy cycle diagram below and answer the questions that follow

(i) What does ∆H1 represent?
(ii) Show the relationship between ∆ H1, ∆H2 and ∆H3

(e) Butane and propane are constituents of a cooking gas. Which produces more energy per
mole on combustion? Explain

  1. The table below gives standard electrode potentials for the metals represented by the Letters
    D, E, F and G. study it and answer the questions that follow.
    Metals Standard electrode potential (volts)
    D -0.13
    E -0.85
    F +0.34
    G – 0.76
    (a) Which metal can be displaced from a solution of its salts by all the other metals in the table? Give a reason ( 2 mks)
    (b) Metals F and G were connected to form a cell as shown in the diagram below

(i) Write the equation for the reactions that occur at electrodes
F
G
(ii) On the diagram, indicate with an arrow the direction in which electrons would flow on
the diagram above
(ii) What is the function of the salt bridge? ( 1 mk)
(c) An electric current was passed through a concentrated solution of copper (II) chloride as
shown in the diagram below

(i) Explain the observation that would be made on the electrolyte as the experiment
progresses ( 2 mks)

(ii) After sometime, test- tube H was found to contain a mixture of two gases. Explain this
observation ( 3 mks)

(iii) Which of the electrodes is the anode? Explain ( 2 mks)

  1. (a) Candle wax is mainly a compound consisting of two elements.
    Name the two elements ( 2 mks) (b) The set- up below was used to investigate the burning of a candle study it and answers the questions that follow

(i) What would happen to the burning candle if the pump was turned off? Give reasons

(ii) State and explain the changes in mass that are likely to occur in tube N by the end of the experiment ( 3 mks)
(iii) Name two gases that come out through tube M ( 2 mks)
(iv) Name another substance that could be used in the place of calcium oxide in tube N

  1. (a) Name one ore from which copper metal is extracted ( 1 mk)
    (b) The chart below shows a sequence of reactions starting with copper.
    Study it and answer the questions that follow

(i) Identify
Gas P ( 1mk)
Reagent Q ( 1 mk)
Solid R ( 1 mk)
(ii) Write an equation for the reaction that takes place in step 5
(iii) State the observations made in steps 4 and 7 ( 2 mk)
Step 4
Step 7 ( 1mk)
(c) Bronze is an alloy of copper and another metal
(i) Name the other metal ( 1mk)
(ii) Give one use of Bronze ( 1mk)

  1. (a) Write the structural formula of:
    (i) Methanol
    (ii)Methanoic acid ( 1mk) (b) Write the equation for the reaction between methanoic acid and aqueous
    sodium hydroxide ( 1mk) (c) (i) Name the product formed when methanol reacts with methanoic acid
    (ii) State one condition necessary for the reaction in (c) (i) above to take place (d) (i) Describe one chemical test that can be used to distinguish between hexane and
    hexane ( 2 mks)
    (ii) State one use of hexane (1mk)
    (iii) Hydrogen reacts with hexane to form hexane. Calculate the volume or hydrogen
    gas required to convert 42g of hexane to hexane at S.T.P ( C=12.0, H=1.0, molar gas volume at S.T.P is = 22.4 litres) ( 4 mks)

CHEMISTRY PAPER 233 / 1 K.C.S.E 2003
QUESTIONS
Some sodium chloride was found to be contaminated with copper (ll) oxide.
Describe how a sample of sodium chloride can be separated from the mixture

Study the information in the table and answer the questions that follow

Ion Electronic
arrangement Ionic
radius
Na+ 2.8 0.095
K+ 2.8.8 0.133
Mg2+ 2.8 0.065

Explain why the ionic radius of ( 1mk)
K+ is greater than that of Na+

Mg2+ is smaller than that of Na+
Use the following equations to determine the heat evolved when aluminum metal is reacted with iron (III) oxide ( 3 mks)
2Al(s) + 3/2 O2(g) →Al2O3(s), ∆ H1 3.6736Kj Mol-1

2Fe(s) + 3/2O2¬ (g) → Fe2O3(s); ∆H2 = 836.81J mol-1

2AL(s) + 3/2 O2 →Al2O3, ∆H = -1673.6 Kjmol-1
Fe2 O3 →2Fe + 3/2 O2, ∆H = 836.8 KJ mol

2Al(s) + Fe2O3(s) →Al2O3 + 2Fe(s) ∆H = 836.8
(a) Sulphur exists in two crystalline forms
(b) Name one crystalline form of sulphur ( 1mk)

An atom of hydrogen can form two ions. Write two equations to show how  a neutral  atom of hydrogen can form two ions. In each case show the sign  of  the energy change involved.

H →H+ + e ( ½ ) ∆H is +Ve ( ½ )
H + e → H- ( ½ ) ∆ H is –Ve ( ½ )
When excess dilute hydrochloric acid was added to sodium , 960cm3 of sulphur (IV) oxide gas was produced. Calculate the mass of sodium sulphite that was used. (molar mass of sodium = 126 g and molar gas volume= 24000cm3 ( 3mks)
In an experiment equal amounts of magnesium powder were placed into test – tube 1 and 2 as shown below

Explain why the amount of hydrogen gas liberated in test – tube 2 is greater than in test- tube 1 before the reaction is complete.

(a) what is meant by heat of vaporization               ( 3 mks)

(b) The boiling points of ethanol, propanol and butanol are780C, 97.20 and 1170C.
explain this trend ( 1 mk)
The set – up below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 800C and 1100C.

name B
What  is the purpose of the thermometer         ( 1mk)
Which liquid was collected in the test tube?            ( 1mk)
An oxide  of  element F has the formula F2O5            ( 1 mk)
Determine the oxidation state  of F
In which  group of  the  periodic- table is element F       ( 1mk)
Yellow phosphorous reacts with chlorine gas to form a yellow liquid. The liquid fumes when exposed to air. Explain these observations           ( 2 mks)
When steam was passed over heated charcoal as shown  in the diagram below, hydrogen and carbon monoxide gases were formed







(a) Write the equation for the reaction which takes place       ( 1 mk)
(b) Name two uses of carbon monoxide gas, which are also  uses of hydrogen  gas
                                    (  2 mks)
Nitrogen (II) oxide and nitrogen (IV) oxide are some of the gases released from car exhaust pipes. State how these  gases affect the environment
A few crystals of potassium permanganate were carefully placed into water in a beaker at one spot.  The beaker was left undisturbed for two hours. State and explain the observation that was made.                             (2mks)
Oleum (H2S2O7) is  an  intermediate product in the industrial manufacture of sulphuric acid
How is oleum converted into sulphuric acid?                 (1 mk)
Give one  use of sulphuric acid                     ( 1mk)
Air was passed through several reagents as shown in the flow chart below







Write an equation for the reaction, which takes place in chamber with  magnesium powder
Name one gas, which escapes from the chamber containing magnesium powder. Give a reason for your answer.                        (2mks) 
Ammonium nitrate was gently heated and the  products collected as shown  in the diagram below.

Describe one chemical and one physical method that can be used to identify gas G.
The table below shows the tests carried out on a sample of water and the results obtained.
Tests Results
I Addition of sodium hydroxide solution White precipitate which dissolves in excess
II Addition of excess aqueous ammonia Colourless solution obtained
III Addition of dilute hydrochloric acid and barium chloride White precipitate

a)  Identify the anion present in the water
b)  Write an ionic equation for the reaction in III
c)  Write the formula of the complex ion formed in II
In the Haber process, the  optimum yield of ammonia  is obtained  when  a temperature of 4500C, a pressure  of 200 atmospheres and an ion catalysts are used

N2(g) + 3H2 (g) 2NH3 (g); ∆H = -92kJ.

How would the yield of ammonia be affected if the temperature was raised to 6000C?                                  ( 2mks)
Give one use of  ammonia                        ( 1mk)
Brass is an alloy of zinc and copper. Give one use of brass         ( 1mk)
An organic  compound with  the formula C4 H10 O reacts  with potassium metal to give hydrogen  gas  and white solid
Write  the structural formula of the  compound
To which homologous series does the compound belong?
Write  the equation for the reaction  between the compound and potassium metal

( 1mk)

  1. The set – up below was used to prepare hydrogen chloride a gas and react it with iron powder. Study it and answer the questions that follow.

At the end of the reaction, the iron powder turned into a light green solid.
Identity the light green solid.(1mk)
At the beginning of the experiment, the Ph of the solution in container L was about 14.. At the end, the pH was found to be 2. Explain(2mks)

  1. a) State the observation made when excess pentane is reacted with bromine gas
    b) Name the compound formed in (a) above.(1mk)
  2. Explain why the reactivity of group (vii) elements decreases down the group
  3. The graph below shows the behaviour of a fixed mass of a gas at constant temperature. a) What is the relationship between the volume and the pressure of the gas?
    b) 3 litres of oxygen gas at one atmosphere pressure were compressed to two
    atmospheres at constant temperature. Calculate the volume occupied by the oxygen gas (2mks)
    Ammonia gas was passed into water as shown below What is the relationship between the blouse and the pressure of the gas?(1mk)
    3 litres of oxygen gas at one atmosphere pressure were compressed to two atmospheres at constant temperature. Calculate the volume occupied by the oxygen gas. (2mks)
    During purification of copper by electrolysis, 1.48g of copper were deposited when current was passed through aqueous copper(II) sulphate for 21/2 hours. Calculate (CU = 63.5, 1 Faraday = 96,500C).

CHEMISTRY PAPER 233/2 K.C.S.E 2003
QUESTIONS

  1. a) The chart below is an outline of part of the periodic table.

With the help of vertical and horizontal lines, indicate the direction of increasing metallic nature of the elements. (2mks)
Which types of elements are represented in the shaded area? (1mk)
b) i) Element A is the same group of the periodic table as chlorine.
Write the formula of the compound formed when A reacts with
potassium metal.(1mk)
ii) What type of bonding exists in the compound formed in (b) (l) above?
Give a reason for your answers. (3mks)
c) Starting with aqueous magnesium sulphate, describe how you would obtain a
sample of magnesium oxide. (3mks)
d) Write two ionic equations to show that aluminium hydroxide is amphoteric (2mk)

  1. a) The diagram below is a cross- section of a dry cell. Study it and answer
    the questions that follow. i) On the diagram, show with a (+) sign the positive terminal
    ii) Write the equation for the reaction in which electrons are produced
    iii) The zinc can is lined with ammonium chloride and zinc chloride paste.
    iv) Give one advantage and one disadvantage of dry cells.

b) The set – up below was used to (electrolyse roller lead (II) ionide.

i)  State the observation that was made at the anode during the electrolysis.

Give a reason for your answer.(2mk)
ii) A current of 0.5 A was passed for two hours. Calculate the mass of lead
that was deposited (pb = 1F = 9,500C) (3mks)

  1. a) State two differences between chemical and nuclear reactions(2mks)
    b) Below is a radioactive decay series starting from 21483 Bi and ending
    at 10682 pb. Study it and answer the question that follows.

i) Identify the particles emitted in steps I and III (2mks)
I
II
ii) Write the nuclear equation for the reaction which takes place
in step V(1mk)
The table below give the percentages of a radioactive isotope of Bismuth that
remains after decaying at different times.
Time (min) 0 6 12 22 38 62 100
Percentage of Bismuth 100 81 65 46 29 12 3
i) On the grid provided, plot a graph of the percentage of Bismuth remaining
(Vertical axis) against time.
ii) Using the graph, determine the:
I. Half – life of the Bismuth isotope
II. Original mass of the Bismuth isotope given that the mass that remained
after 70 minutes was 0.16g (2mks)
d) Give one use of radioactive isotopes in medicine (1mk)

  1. Excess marble chips (calcium carbonate ) was put in a beaker containing 100cm3 of dilute hydrochloric acid. The beaker was then placed on a balance and the total loss in mass recorded after every two minutes as shown in the table below.
    Time(min) 0 2 4 6 8 10
    Total loss in mass (g) 0 1.8 2.45 2.95 3.2 3.3

a) Why was there a loss in mass? (1mk)
b) Calculate the average rate of loss in mass between:
i) 0 and 2 minutes (1mk)
ii) 6 and 8 minutes (1mk)
iii) Explain the difference in the average rates of
reaction in (b) (i) and (ii) above (2mks)
c) Write the equation for the reaction which takes place in the beaker
d) State three ways in which the rate of the reaction above could be increased(3mk)
e) The solution in the beaker was evaporated to dryness what would happen if the open beaker and its contents were left in the laboratory overnight.(2mks)
f) Finally some water was added to the contents of the beaker.
When aqueous sodium sulphate was added to the contents of the beaker, a white precipitate was formed. (1mk)
i) Identify the white precipitate
ii) State one use of the substance identified in (f) (i) above (1mk)

  1. The basic raw material for extraction of aluminium is bauxite
    a) Name the method that is used to extract aluminium from bauxite
    b) Write the chemical formula of the major component of bauxite
    c) i) Name two major impurities in bauxite (2mks)
    ii) Explain how the impurities in bauxite are removed (3mks)
    d) Cryolite is used in the extraction of aluminium from bauxite.
    State its function (1mk)
    f) Aluminium is a reactive metal yet utensils made of aluminium do not corrode easily. Explian this observation (2mks)
  2. The set – up below was used to prepare hydrogen gas a) Complete the diagram to show how a dry sample of hydrogen gas
    can be collected(3mks)
    b) Write an equation for the reaction, which takes place when hydrogen
    gas burns in air.(1mk)
    c) i)1.2 litres of hydrogen gas produced at room temperature and pressure when 3.27g of zinc was used. Determine the relative atomic mass of zinc.(Molar gas volume is 24 litres) 4mks
    d) State two industrial uses of hydrogen gas.
  3. a) State how burning can be used to distinguish between ethane and ethyne.
    Explain your answer.(3mks)
    b) Draw the structural formula of the third member of the homologous
    series of ethyne.
    c) The flow chart below shows a series of reactions starting with ethanol.
    Study it and answer the questions that follow. i) Name :
    I. Process A
    II. Substances B and C
    B
    C
    ii) Write the equation for the combustion of ethanol (1mks)
    iii) Explain why it is necessary to use high pressure to change gas B
    into the polymer (1mk)
    iv) State one use of methane (1mk)

K.C.S.E 2004 CHEMISTRY PAPER 233/1
QUESTIONS

  1. When a candle was brunt completely. The total mass product was found to be greater than the original mass of the candle. Explain
  2. Ammonium nitrate was heated as shown in the set-up below (2 marks) a) Identify gas a.
    b) State explain precaution that must be taken before heating id dropped.
  3. The table below the first ionization energies of elements B and C.

Element Ionisation energy KJ mol-1
B
C 494
736

What do these values suggest about the reactivity of B compared to that of C? Explain (2mks)

  1. Dilute hydrochloric acid and solid sodium sulphite were reacted as shown in the set-up below a) Name the gas produced in the flask (2mks)
    b) Give two reasons why no gas was collected in the gas jar. (2mks)
  2. Copper(II) sulphate reacts with barium chloride according to the equation below.
    CuSO4(aq) + BaCl2(aq) CuCl2(aq) + BaSO4(s) ; H = – 17.7kj mol -1
    Calculate the temperature change when 900cm3 of m copper (II) sulphate were added to 600cm3 of 1M Barium (II) chloride.
  3. Both diamond and graphite have giant atomic structures. Explain why diamond is hard while graphite is soft. (3mks)
  4. Nitrogen forms many compounds in which its oxidation state varies.
    a) What is meant by oxidation state? (1mk)
    b) What is the oxidation state of nitrogen in Mg3M2 (1mk)
  5. When wood is burnt, a grey powder called ash remains. The ash is stirred with water and filtered, a colourless solution is obtained.
    a) What is the main component of the colourless solution?(1mk)
    b) Explain your answer in (a) above(2mks)
  6. Study the information in the table below and answer the questions that follows.

Alcohol Heat of combustion on KJ mol-1
Methanol
Ethanol
Propanol
Butanol 715
1371
2010
2673

Give a reason why the difference in the molar heats of combustion between successive alcohols are close.                    (3mks)
  1. Explain why a high temperature is required for nitrogen of react with oxgen(1mk)
  2. Study the flow chart below and answer the questions that follow. a) State the condition necessary for the reaction in step 2 to occur (1mk)
    b) Name:
    i) Gas D (1mk)
    ii) One use of zinc (1mk)
  3. Starting with aluminium sulphate, describe how a solid sample of aluminium hydroxide could be prepared. (3mks)
  4. a) What is the name given to the smallest repeating unit of a polymer.(1mk)
    b) Draw the structure of the smallest repeating unit of a polyvinyl chloride (1mk)
  5. When X cm3 of a solution of 0.5m magnesium carbonate was 8.4g.
    a) Write the ionic equation for the reaction that took place(1mk)
    b) Calculate the value of X. (C = 12.0, Mg 24.0; 016.0 (2mks)
  6. In an experiment, a student put equal volumes of mixtures of ethanoic acid in water and ethanoic acid in hexane in two test – tubes as shown below. In each test tube, equal amounts of solid sodium hydrogen carbonate were added. a) State the observation which was made in each test – tube(1mk)
    Test tube 1
    Test tube 2
    b) Explain the observation in (a) above (2mks)
  7. Four metal F,G,H and J were each separately added to cold water, and steam. The table below is a summary of the observations made and the formulae of the hydroxides formed.

Metal Cold water Hot water Steam Formula of Hydroxide
F Reacts slowly Reacts fast Reacts very fast F(OH)2
G No reaction No reaction No reaction –
H Fast Reacts very fast Reacts explosively HOH
J No reaction Reacts slowly Reacts fast J(OH)2

a)  Which two elements are likely to be in the same group of the periodic table?

b) Arrange the metals in the order of their reactivity starting with the most reactive (2mks)

  1. Name the organic compound formed when CH3CH2CH2CH2CH2OH is reacted with concentrate sulphuric acid at 170oC (1mk)
  2. Carbon monoxide gas passed over heated Iron (III) as shown in the diagram below.

a) Give the observation made in tube P.(1mk)
b) Write the equation for the reaction which takes place in tube P. (1mk)

  1. Astrip of metal Q was dipped into a solution of copper (II) sulphate and allowed to stand overnight. Give that:
    Cu2+ + 2e  Cu(s) ; Eø = + 0.34v
    Q2+(aq) + 2e  Q(s) ; Eø = – 0.13v
    a) State the observations which were made(2mks)
    b) Give a reason for your answer in 19 (a) above.(1mk)
  2. State two factors which determine the stability of an isotope. (2mks)
  3. The react between a piece of magnesium ribbon with excess 2m hydrochloric acid was investigated at 25oC by measuring the volume of hydrogen gas produced as the reaction progressed. The sketch below represents the graph that was obtained. a) Name one piece of apparatus that may be used to measure the
    volume of hydrogen gas produced.
    b) On the same diagram, sketch the curve that would be obtained if the experiment when excess chlorine gas was bubbled into hot concentrated sodium hydroxide, the following reaction occurred.
    3Cl2(g) + 6NaOH(aq) NaCO3(aq) + 5NaCl(aq) 3H2O(l)
    In which product did chorine undergo oxidation? Explain(3mks)
  4. 1cm3 of soap was added to two test – tubes each containing water obtained from different sources. The lather produced in each test tube is represented as shown in the diagram below. Explain why there is more lather intest – tube 2 than intest – tube 1.(3mks)
  5. Carbon dioxide can be dissolved in water under pressure to make an acidic solution.
    a) What is meant by an acidic solutions?(1mk)
    b) aqueous lead (II) nitrate reacts with the acidic solution to form a precipitate.
    Write anionic equation for the reaction.(1mk)
  6. Below is a sketch of a reaction profile. a) On the diagram, show the heat of reaction, H.(1mk)
    b) State and explain the type of reaction represented by the profile(2mks)
  7. The diagram below represents the set – up that was used to study the effect of an electric current on pure water and dilute sulphuric acid. State and explain the observation made when each experiment was started.(3mks)
  8. Apiece of chromatography paper was spotted with coloured inks obtained from pens labeled 1 to 6. The diagram below shows the spots after the chromatogram was developed. a) Which two pens contained in the same pigment?(1mks)
    b) Which pens contained only one pigment(1mk)
    c) According to the chromatogram, which pigments are present in the
    ink of pen number 6.(1mk)

CHEMISTRY PAPER 233/2.
K.C.S.E 2004

  1. a) The table below shows properties of chlorine, bromine and iodine.
    Element Formula Colour and state room temperature Solubility
    Chlorine
    Bromine
    Iodine Cl2
    Br2
    l2 i)…………………
    Brown liquid
    iii) ………………. Soluble
    ii)………………
    Slight soluble
    Complete the table by giving the missing information in (i),(ii) and (iii) (3mks)
    b) Chlorine gas is prepared by reacting concentrated hydrochloric acids with manganese (iv) oxide.
    i) Write the equation for reaction between concentrated hydrochloric acid and manganese (iv) oxide. (1mk)
    ii) What is the role of manganese (Iv) oxide in this reaction (1mks)
    c) i) Iron (II) chloride reacts with chlorine gas to form substance E.(1mk)
    Identify substance E
    ii) During the reaction in c(i) above,6.30g of iron chloride were converted to 8.06 of substance E. Calculate the volume of chlorine used.
    (Cl = 35.5, Molar gas volume at room temperature = 24000cm3, Fe =56 (mks)
    d) Draw and name the structure of the compound formed when excess chlorine gas is reacted with ethane gas. (2marks)
    e) Give the industrial use of chlorine (1 mk)
  2. a) The set-up below was used to collect gas F, produced by the reaction
    between water and calcium metal. (i) Name gas f
    (ii) At the end of the experiment, the solution in the beaker was found to be a
    weak base. Explain why the solution is a weak base. (2 marks)
    (iii) Give one laboratory use of the solution formed in a beaker. (1 mark)
    (b) The scheme below shows some reactions starting with calcium oxide. Study it and answer the questions that follow. (i) Name the reagents used in steps 2 and 4 (2marks)
    Step 2 ……….
    Step 4 ……….
    (ii) write an equation for the reaction in step 3. (1 mk)
    (iii) Describe how a solid sample of anhydrous calcium sulphate is obtained in
    Step 5
  3. a) The diagram below illustrates how sulphur/extracted by the Frisch process. Label the pipe through which superheated water is pumped in (1mk) b. The equation below shows the oxidation of sulphur dioxide to sulphure trioxide in
    the contact process.
    2SO2(g) + O2(g) 2SO3(g); H = – 196kJ

(i) Name one catalyst for this reaction (1 mark)
(ii) State and explain the effect on the yield of sulphur trioxide when:
I The temperature increased (2mks)
II The amount of oxygen is increased (2mks)
(iii) Describe how sulphur trioxide is converted to sulphuric acid in the contact process. (2 marks)
(c) State two disadvantages of having sulphur dioxide in the environment (2mks)
(d) Ammonia sulphate is a fertilizer produced by passing ammonia gas into concentrated sulphuric acid.
(i) Write the equation for the reaction (1mk)
(ii) Calculate the mass in Kg of sulphuric acid required to produce 25kg of the
fertilizer (S= 32.0; O= 16.0; N = 1.0)

  1. a) at 250C , 50g of potassium were added to 100gm of water to make a saturated
    solution. What is meant by a saturated solution? (1 mk)
    b) The table below gives the solubilities of potassium nitrate at different
    temperatures.
    Temperature 0C 12 20 28 36 44 52
    Solubility g/100g C water 22 31 42 55 70 90
    (i) Plot graph of the solubility of potassium nitrate (vertical axis) against temperature
    (3 marks)
    (ii) Using the graph:
    I Determine the solubility of potassium nitrate at 150C
    II Determine the mass of potassium nitrate that remained undissolved given
    that 80g of potassium nitrate were added to 100cm3 of water and warmed to 400C.
    c) Determine the molar concentration of potassium nitrate at 150C (3mks)
    (Assume there is no change in density of water at this temperature)
    (K = 39. 0; N= 14.0; O = 16.0)
  2. The flow chart below shows some reactions starting with lead (II) nitrate. Study it and answer the questions that follow. (i) State the condition necessary in step 1.
    (ii) Identify:
    I Reagent K
    II Gas q
    III Acidic products S and R
    (iii) Write:
    I The formula of the complex ion formed instep 3. (1mk)
    II The equation of the reaction in step 4 (1 mk)
    b) The use of materials made of lead in roofing and in water pipes is being discouraged
    State:
    (i) Two reasons why these materials have been used in the past. (2mks)
    (ii) One reason why their use is being discouraged
    c) (i) The reaction between lead (II) nitrate and concentrated sulphuric acid starts but stops immediately. Explain (2mks)
  3. a) Crude oil is a source of many compounds that contain carbon and hydrogen only.
    (i) Name the processes used to separate the components of crude oil (1mk)
    (ii) On what two physical properties of the above components does the separation depend? (2mks)
    b) Under certain conditions, hexane can be converted to two products.
    The formula of one of the products is C3H3
    (i) Write the formula of the other product (1mk)
    (ii) Describe a simple chemical reaction to show the difference between the two products formed in (b) above. (2mks)
    c) Ethane, C2H2 is another compound found in crude oil.
    One mole of ethane was reacted with one mole of hydrogen chloride gas and a product p1 and was formed. P1 was then reacted with excess hydrogen gas to form p2. Draw the structures p1 and p2.
    d) The set-up below was used to prepare and collect ethane gas. Study it and answer the questions that follow. (i) Name the substance T
    (ii) Give the property of ethane that allows it to be collected as shown in the set up.
    e) One of the reactions undergone by ethane is addition polymerization. Give the name of the polymer and one disadvantage of the polymer it forms. (2 marks)
    Name the polymer.
    Disadvantage of the polymer
  4. (a) Brine usually contains soluble calcium and magnesium salts. Explain how
    sodium carbonate is used to purify brine. (2mks)
    b) The diagram below represents a diaphragm cell used to electrolysed pure brine i) Write the equations for the reactions that take place at I Cathode (1mk) II Anode (1mk) ii) Name: I Product at U (1mk) II Another material that can be used instead of titanium (1mk) III The impurity present in the product at U iii) State two functions of the diagram (2mks) c) Give one industrial use of the product at U. (1 mk)

CHEMISTRY PAPER 233/1 K.C.S.E 2005
QUESTIONS

  1. State one use of sodium hydrogen carbonate. (1 mark)
  2. Calcium oxide can be used to dry ammonia gas. (2 mark)
    a) Explain why calcium oxide is not used to dry hydrogen chloride gas (2 mark)
    b) Name one drying agent for hydrogen chloride gas
  3. The set-up below was used to demonstrate the effect of heat on hard water Name substance A. (1 mark)
    Explain why the heating of hard water produced substance A. (2marks)
  4. Using dots (.) and crosses(x) to represent electrons, show bonding in the compounds formed when the following elements react: (si = 14, Na = 11 and Cl = 17) (1 mark)
    a) Sodium and chlorine (1 mark)
    b) Silicon and chlorine (1 mark)
  5. Zinc oxide reacts with acids and alkalis
    a) Write the equation for the reaction between zinc oxide and:
    i) Dilute sulphuric acid (1mark)
    ii) Sodium hydroxide solution (1 mark)
    b) What property of zinc oxide is shown by the reaction in (a) above? (1 mark)
  6. Use the information in the table below to answer the questions that follow. (The letters do not represent the actual symbols of the elements)

Element B C D E F
Atomic number 18 5 3 5 20
Mass number 40 10 7 11 40

a)  Which two letters represent the same element?  Give a reason.   (2marks)
b)  Give the number of neutrons in an atom of element D     (1 mark)
  1. Give the name and draw the structural formula of the compound formed when one mole of ethane reacts with one mole of chlorine gas.
    8 Determine the oxidation state of sulphure in the following compounds: (2 marks)
    a) H2S………………………………………………………………………………..
    b) Na2S………………………………………………………………………………
  2. A certain carbonate, GCO3, reacts with dilute hydrochloric acid according to the equation given below:
    GCO3(s) + 2HCL(aq) GCl2 (aq) + (CO2(g) + H2O(l)

If 1 g of the carbonate reacts completely with 20 cm3 of 1 M hydrochloric acid ,calculate the relative atomic mass of G
(C = 12.0 = 16.0)
10 The sketch completely with substance H is converted into J. study it and answer the question that follows.

Why do the two curves become horizontal after sometime?
  1. The reaction between how concentrated sodium hydroxide and chlorine produces sodium
    chlorate (V), sodium chloride and water
    (a) Write the equation for the reaction
    (b) Give one use of sodium chlorate (V)
  2. In the industrial extraction of lead, the ore is first roasted in a furnace. The solid mixture
    obtained is then fed into another furnace together with coke, limestone and scarp iron. State the function of each of the following in this process: ( 3 mks)

(a) Coke
(b) Limestone
(c) Scrap iron
13. Methane reacts with oxygen according to the equation given below.
CH4 (g) + 202 (g) →CO2 (g) + 2H2O (l), ∆H = 890 KJ MOL-1
Calculate the volume of methane which would produce 111.25 kj when completely burnt.
(Molar volume of a gas = 24 litres.) (2 mks)
14. 100 g of a radioactive substance was reduced to 12.5 g in 15.6 years. Calculate the half –
life of the substance. (2 mks)
15. In terms of structure and bonding, explain why graphite is used as a lubricant. (2mks)
16. The table below gives some information about elements I,II,III and IV which are in the
same group of the periodic table. Use the information to answer the questions that follows.

Element First Ionisation energy
(kjmol-1) Atomic Radius (nm)
I 520 0.15
II 500 0.19
III 420 0.23
IV 400 0.25

State and explain the relationship between the variations in the first ionization energies and the atomic radii. ( 3 mks)

  1. (a) what condition is necessary for an equilibrium to be established? ( 1 mk)
    (b) When calcium carbonate is heated, the equilibrium shown below is established
    CaCO3 (s) CaO(s) + CO2(g)
    How would the position of equilibrium be affected if a small amount of dilute potassium hydroxide is added to the equilibrium mixture? Explain ( 2 mks) In an experiment to investigate the conductivity of substances, a student used the set – up shown below. The Student noted that the bulb did not light (1mk)
    What had been omitted in the set- up?
    Explain why the bulb lights when the omission is corrected ( 2 mks)
    The scheme below shows the energy changes that are involved between ice, water and steam. Study it and answer the questions that follow

∆H1 ∆H2
H2O(s) HO(l) H2O(g)
∆H4 ∆H3
(a) What name is given to the energy change, ∆H4? ( 1mk)
(b) What is the sign of ∆H3? Give a reason ( 2 mks)

Equal volumes of 1M monobasic acids L and M were each reacted with excess magnesium  turnings. The table below shows the volumes of the gas produced after one  minute.

Acid Volume of gas (cm3)
L
M 40
100

Explain the differences in the volumes of the gas produced          ( 2 mks)

The diagram below shows a set- up that was  used to prepare and collect a sample of nitric acid




















Give a reason why it is possible to separate nitric acid from  sulphuric acid  in the set – up                              ( 1 mk)
Name another substance that can be used  instead  of potassium nitrate 

( 1 mk)
Give one use of nitric acid (1 mk)

Study the flow chart below and answer the questions that follow

(a) Identify N and P ( 2 mks)
N………………………………………………………………………………………
P ………………………………………………………………………………………..

(b) What name is given to the type of halogenations/ chlorination reaction in step 2?

The set – up below was used to obtain a sample  of iron











Write two equations for the reactions which occur in the combustion tube    ( 2mks)

In an experiment, a gas jar containing  most sulphur  dioxide was  inverted over another gas jar containing  hydrogen sulphide  gas
State and explain the observation that was made         ( 2mks)
State the precaution that should be taken when carrying out this experiment (1mk)

When a few drops of aqueous ammonia were added to copper (II) nitrate solution, a light tube precipitate was formed.  On addition of more aqueous ammonia, a deep blue solution was formed.

Identify the substance responsible for the:
Light blue precipitate ( 1mk)
Deep blue solution ( 1mk)
When a current of 0.82A was passed for 5 hours through an aqueous solution of metal Z, 2.65 g of the metal were deposited. Determine the charge on the ions of metal Z. ( 1 Faraday = 96500 Coulombs:
Relative atomic mass of Z = 52
Dry carbon monoxide gas reacts with heated lead (II0 oxide as shown in the equation below
PbO(s) + CO(g) →Pb (s) + CO2 (g)
(a) Name the process undergone by the lead (II) oxide (1 mk)
(b) Give a reason for your answer in (a) above ( 1mk)
(c) Name another gas that can be used to perform the same function as carbon monoxide gas in the above reaction.

When a hydrocarbon was completely burnt in oxygen, 4.2g of carbon dioxide and 1.71 g of water were formed. Determine the empirical formula of the hydrocarbon

(H= 1.0 ; C=12.0 ; 0 = 16.0) ( 3 mks)

CHEMISTRY PAPER 233/2 K.C.S.E 2005
QUESTIONS

  1. (a) The diagram below shows spots of pure substance A,B, and C on a chromatography
    paper. Spot D is that of a mixture

After development, A, B and C were found to have moved 8cm, 3cm and 6 cm respectively. D has separated into two spots which had moved 6cm and 8 cm
(i) On the diagram
I Label the baseline ( origin) ( 1mk)
II Show the positions of all the spots after development ( 3 mks)
(ii) Identify the substances present in the mixture D ( 2mks)
(b) Describe how solid ammonium chloride can be separated fro a solid mixture of ammonium chloride and anhydrous calcium chloride ( 2mks)
(c) The table shows liquids that are miscible and those that are immiscible

Liquid L3 L4
L1 Miscible Miscible
L2 Miscible Immiscible
Use the information given to answer the questions that follow
(i) Name the method that can be used to separate L1 and L3 from a mixture of two
( 1 mk)
(ii) Describe how a mixture of L2 and L4 can be separated ( 2mks)

  1. (a) Name one raw material which sodium hydroxide is manufactured ( 1 mk)
    (b) Sodium hydroxide pellets were accidentally mixed with sodium chloride 17.6 g of the mixture were dissolved in water to make one litre of solution. 100 cm3 of the mixture were dissolved in water to make one litre solution. 100cm3 of the solution was neutralized by 40cm3 of 0.M sulphuric acid
    (i) Write an equation for the reaction that took place
    (ii) Calculate the:
    (i) Number of moles of the substance that reacted with sulphuric acid ( 2mks)
    (ii) Number of moles of the substances that would react with sulphuric acid in the
    one litre of solution ( 1mk)
    (iii) Mass of the unreacted substances in one litre of solution ( 2 mks)
    (H = 1,0 ; Na = 23.0 ; Cl= 35.5 ; 0= 16.0)
    (c) The diagram below shows an incomplete set-up used to prepare and collect ammonia gas

(i) Name solid M ( 1 mk)
(ii) Complete the diagram to show how a dry sample of ammonia gas can be collected
( 3 mks)
(d) In an experiment, excess ammonia gas passed over heated copper (II) oxide on a
combustion tube.
(i) State the observation that was made in the combustion tube at the end of the experiment ( 1 mk)
(ii) What property of ammonia is shown in the above reaction (1 mk)
(iii) Name one use of ammonia (1 mk)

  1. (a) The table below shows the standard reduction potentials for four half- cells.
    Study it and answer the questions that follow. (Letters are not the actual symbols of the elements)
    Eθ (volts)
    F2(aq) + 2e →2F (aq) ; + 0.54
    G2+(aq) + 2e →G(s) ; -0.44
    H2+(aq) + 2e →H(s) ; + 0.34
    2j+(aq) + 2e →J2 ; 0.00
    (i) Identify the strongest reducing agent ( 1 mk)
    (ii) Write the equation for the reaction which takes place when solid G is added to a
    solution containing H2+ ions ( 1 mk)
    (iii) Calculate the Eθ value for the reaction in (ii) above ( 1mk)

(b) The diagram below shows the apparatus that can be used to electrolyze acidified water to obtain hydrogen and oxygen gases. Study it and answer the questions that follow

(i) Identify the electrode at which oxidation takes place ( 1 mk)
(ii) Give a reason why it is necessary to acidify the water ( 1mk)
(iii) Explain why hydrochloric acid is not used to acidify the water ( 2mks)
(c) During electrolysis of aqueous copper (II) sulphate, 144750 coulombs of electricity were
used.
Calculate the mass of copper metal that was obtained
Cu = 64 ; 1 Faraday = 96500 coulombs) ( 3 mks)

  1. (a) An atom Q can be represented as
    52
    Q
    24
    What does the number 52 represent? ( 1mk)
    (b) Study the information in the table below and answer the equations that follow
    (Letters are not the actual symbols of the elements)

Element Electronic
Arrangement of stable ion Atomic
Radius
(nm) Ionic
Radius
(nm)
N 2.8.8 0.197 0.099
P 2.8.8 0.099 0.181
R 2.8 0.160 0.065
S 2.8 0.186 0.095
T 2 0.152 0.068
U 2.8 0.072 0.136
(i) Write the formula of the compound formed when N reacts with P. (atomic numbers are N = 20; P = 17) ( 1 mk)
(ii) Identify the elements which belong to the third period of the periodic table. Explain ( 2 mks)
(iii) Which of the element identified in b (ii) above comes first in the third period? Explain ( 2 mks)
(iv) Select two elements which are non- metals ( 1 mk)
(c) The table below gives some properties of substances I, II, III, and IV. Study it and answer the questions that follow

Substance Electrical conductivity M.P (0C) B.P (0C)
Solid Molten
I Does not conduct Conducts 801 1420
II Conducts Conducts 650 1107
III Does not conduct Does not conduct 1700 2200
IV Does not conduct Does not conduct 113 440

(i) What type of bonding exists in substances I and II ( 2mks)
I
II
(ii) Which substances is likely to be sulphur? Explain ( 2mks)

  1. In an experiment, a piece of magnesium ribbon was cleaned with steel wool. 2.4 g of the clean magnesium ribbon was placed in a crucible and completely burnt in oxygen. After cooling, the product weighed 4.0 g
    (a) Explain why it was necessary to clean the magnesium ribbon ( 1mk)
    (b) What observation was made in the crucible after burning ( 1 mk)
    (c) Why was there an increase in mass? ( 1 mk)
    (d) Write the equation for the reaction which took place in the crucible ( 1mk)
    (e) The product in the crucible was shaken with water and filtered. Explain the observation which was made when blue and red litmus papers were dropped into the filtrate.
    ( 3 mks)
  2. (a) The list below shows the formulae of some organic compounds. Use it to answer the questions that follow.
    V1 HC3CH2CH2OH
    V2 CH3CH2CH3 O V3 CH3CH2CH2C – OH
    V4 CH3CH2CH = CH2
    V5 CH3 CH2CH2CH3 (i) Select two compounds which
    I are not hydrocarbons ( 1mk)
    II Belong to the same homologous series ( 1 mk)
    (ii) Identify the compound that is likely to undergo polymerization. Give a reason for your answer. ( 2 mks) The structures below represents two cleansing agents:
    R – COO- Na+
    R – OSO3- Na+

In the table below, give one advantage and one disadvantage of using each one of them

Advantage   Disadvantage

R – COO- Na+
R – OSO3 – Na+
Under certain, ethanoic acid ( C2H4O2) and ethanol (C2H5OH) react to form a sweet smelling compound.
What is the general name of compound to which the sweet smelling compound belong? ( 1mk)
Write the formula of the sweet smelling compound (1 mk)
Give one use of ethanoic acid other the formation of the sweet smelling compounds (1 mk)
Write the equation for the reaction dilute ethanoic acid and solid potassium carbonate ( 1mk)
Fibres are either synthetic or natural. Give one:
(i) Example of a natural fibre ( 1mk)
(ii) Advantage of synthetic fibres have over natural fibres ( 1mk)

  1. (a) Below is a simplified diagram of the Downs Cell used for the manufacture of sodium.
    Study it and answer the questions that follow (i) What material is the anode made of? Give a reason (2 mks)
    (ii) What precaution is taken to prevent chlorine and sodium from re- combination? ( 1 mks)
    (iii) Write an ionic equation for the reaction in which chlorine gas is formed ( 1mk)
    (b) In the Downs process, (used for manufacture of sodium), a certain salt is added to lower the
    melting point of sodium chloride from about 8000C to about 6000C.
    (i) Name the salt that is added (1mk)
    (ii) State why it is necessary to lower the temperature (1mk)
    (c) Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of
    sodium in the Downs process ( 2mk)
    (d) Sodium metal reacts with air to form two oxide. Give the formulae of two oxides ( 1mk)

CHEMISTRY PAPER 1 2006
QUESTIONS

  1. (a) What is meant by isomerism? (1mark)
    (b) Draw and name two isomers of butane. (2 marks)
  2. The diagram below represent a set-up that was used to show that part of air is used during burning.

a) Given that phosphorus used was was in excess, draw a diagram of the set-up at the end of the experiment (when there was no further observable change). (1mk)
b) Suggest one modification that should be made on the apparatus if the percentage of the air used is to be determined. (1mk)

  1. 60cm3 of oxygen gas diffused through a porous partition in 50 seconds. How long would it take 60cm3 of sulphur (IV) oxide gas to diffuse through the same partition under the same conditions? (S= 32.0, 0 = 16.0) (3marks)
  2. a) Complete the nuclear equation below. (1mark) b) 37 37 A……. B18 17</code></pre></li>

(b) State one:
(i) Use of radioisotopes in agriculture (1mark)
(ii) Danger associated with exposure of human beings to radioisotopes
(1 mark)

  1. The atomic numbers of elements C and D are 19 and 9 respectively. State and explain the electrical conductivity of the compound CD in:
    (a) Solid state (1 ½ marks)
    (b) aqueous state. (1 ½ marks)
  2. In an experiment to study the properties of concentrated sulphuric acid, a mixture of the acid and wood charcoal was heated in a boiling tube.
    (a) write the equation of the reaction that took place in the boiling tube.(1mark)
    (b) Using oxidation numbers, show that reduction and oxidation reactions took place in the boiling tube (2 mark)
  3. A group of compounds called chlorofluorocarbons have a wide range of uses but they also have harmful effects on the environment.
    State one:
    a) Use of chlorofluorocarbons (1 mark)
    b) Harmful effect of chlorofluorocarbons on the environments. (1 mark)
  4. when 94.5g of hydrated barium hydroxide, ba(OH)2. nH2O were heated to constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the empirical formula of the hydrated barium hydroxide. (3 marks)
  5. at 200C, NO2 and N2 O4 gases exist in equilibrium as shown in the equation below
    2 NO2(g) N2O4(g); H = -ve
    Brown pale yellow
    State and explain the observation that would be made when;
    a) A syringe containing the mixture at 200C is immersed in ice-cold water
    (1 ½ mks)
    b) the volume of the gaseous mixture in a syringe is reduced. (1 ½ mks)
    10 Name the process which takes place when:
    a) Solid carbon (IV) oxide (dry ice) changes directly into gas (1 mark)
    b) A red litmus paper turns white when dropped into chlorine water. (1 mark)
    c) Propane gas molecules are converted into a giant molecule (1 mark)
  6. a) water from a town in Kenya is suspected to contain chloride ions but not sulphate ions.
    Describe how the presence of the chloride ions in the water can be shown. (1 mk)
    b) State one advantage of drinking hard water rather than soft water. (1 mk)
  7. The table below shows the relative atomic masses and the percentage abundance of the isotopes L1 of element L.
  8. The diagram below represents the set-up that was used to prepare and collect hydrogen chloride gas in the laboratory. a) State the purpose of concentrated sulphuric acid in the wash bottle. (1 mark)
    b) Write an equation for the reaction between dry hydrogen chloride gas and
    heated iron (1 mark)
    c) Hydrogen chloride gas is dissolved in water to make hydrochloric acid. State one use of hydrochloric acid.
  9. Below is a list of oxides.
    MgO, N2O, K2O, CaO, and Al2O3.
    Select:
    a) A neutral oxide (1 mk)
    b) A highly water soluble basic oxide (1 mark)
    c) An oxide which can react with both sodium hydroxide solution and dilute
    hydrochloric acid. (1 mk)
  10. Study the standard reduction potential given and answer the questions that follow.
    (The letters are not the actual symbols of the elements).
    Eø (volts)
    M2+(aq) + 2e → M(s) -0.76
    N2+(aq) + 2e → N(s) -2.37
    P+(aq) + e → P(s) +0.80
    Q2+(aq) +2e → Q(s): -0.14
    a) The standard reduction potential for Fe 2+(aq) is -0.44 volts. Select the element which would best protect iron from rusting. (1 mark)
    b) Calculate the E ø value for the cell represented as M(s) / M2+ (aq) // p+(aq) /P(s).
    (2mks)
    16 When hydrogen sulphide gas was bubbled into an aqueous solution of iron (III) chloride, a yellow precipitate was deposited. (1mark)
    a) The standard reduction potential for Fe2+ (aq) is -0.44 volts. Select the element which would best protect iron from rusting. (1 mark)
    b) Write an equation for the reaction that took place. (1 mark)
    c) What type of reaction was undergone by hydrogen by hydrogen sulphide in this reaction? (1mark)
  11. The first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia gas.
    (a) What is the name of the catalyst used? (1 mk)
    (b) Write the equation for the catalytic oxidation of ammonia gas. (1mk)
    (c) Nitric acid is used to make ammonium nitrate, state two uses of ammonium
    nitrate. (1 mark)
  12. Study the diagram below and answer the question that follows.

Describe one chemical test that can be carried out to identify substance s. (2 marks)

  1. a) starting from solid magnesium hydroxide. (1mark)
    b) Give one use of magnesium hydroxide. (1 mark)
  2. a) Distinguish between a covalent bond and a co-ordinate bond ( 2 marks)
    b) Draw a diagram to show bonding in an ammonium ion. (1mark)
  3. (a) Explain why the metals magnesium and aluminium are good conductors of electricity. (1 mark)
    b) Other than cost, give two reasons why aluminium is used for making
    electric cables while magnesium is not (2mks)
  4. The diagram below represents part of a set – up used to prepare and collect gas T.

a) Name two reagents that are reacted to produce both carbon (IV) oxide and carbon(II) oxide.(1mk)
b) Write the equation for the reaction which takes place in the wash bottles.(1mk)

c) Give a reason why carbon(II) oxide is not easily detected.(1mk)

  1. Explain why the boiling point of ethanol is higher than that of hexane.
    (Relative molecular mass of ethanol is46 while that of hexane is 86)
  2. a) Complete the table below to show the colour of the given indicator in
    Indicator Colour in
    Acid solution Basic solution
    Methyl orange ……………. Yellow
    Phenolpthalein Colourless ………………
    b) How does the PH value of 0.1 M potassium hydroxide solution compare with that of 0.1M aqueous ammonia? Explain. (2mks)
  3. Study the properties of substances V1 to V4 in the table below and answer
    the questions that follow.
    Substance Solubility in water Solubility Melting Point(oC) Boiling point(oC)
    V1 Insoluble Soluble -30 250
    V2 Insoluble Insoluble 1535 3000
    V3 Insoluble Soluble 16.8 44.8
    V4 Insoluble Soluble 75 320
    a) Which of the substances are liquids at 240C?
    b) Describe how a mixture containing V2 and V4 can be separed (2mks)
  4. The graph below shows a curve obtained when water at 20oC was heated for 15 minutes. a) What happens to the water molecules between points W and x? (1mk)
    b) In which part of the curve does a change of state occur? (1mk)
    c) Explain why the temperature does not rise between points X and Y. (1mk)
  5. Study the flow chart below and answer the questions that follow. a) Name reagent z.
    b) Describe the process which takes place in step 2.(1mk)
    c) Identify the white solid. (1mk)
  6. Study the diagram below and answer the questions that follow. a) What do H1 and H2 represent? (2mks)
    b) Write an expression to show the relationship between H1,H2 and H3.(1mk)

CHEMISTRY PAPER 2 (233/2) 2006
QUESTIONS

  1. a) What is an electrolyte? (1mk)
    b) State how the following substances conduct electricity.
    i) Molten calcium chloride (1mk)
    ii) Graphite. (1mks)
    c) The diagram below shows a set up that was used to electrolyse aqueous magnesium sulphate.

i) On the diagram above, using an arrow, show the direction
of flow of electrons. (1mk)
ii) Identify the syringe in which hydrogen gas would be collected. Explain (1mk)
d) Explain why the concentration of magnesium sulphate was found to have
increased at the end of the experiment. (2mks)
e) During the electrolysis, a current of 0.72A was passed through the electrolyte for 15 munites.Calculate the volume of gas produced at the anode.(1 Faraday = 96 500 coulombs; molar gas volume is 24000cm3 at room temperature). (4mks)

  1. a) In an experiment to determine the molar heat of reaction when magnesium displaces copper ,0.15g of magnesium powder were added to 25.0cm3 of 2.0M copper (II) chloride solution. The temperature of copper (II) chloride solution was 25oC.While that of the mixture was 43oC.
    i) Other than increase in temperature, state and explain the observations which were made during the reaction.(3mks)
    ii) Calculate the heat change during the reaction (specific heat capacity of the solution = 4.2jg-1k-1and the density of the solution = 1g/cm3(2mks)
    iii) Determine the molar heat of displacement of copper by magnesium.(Mg=24.0).
    iv) Write the ionic equation for the reaction.(1mk)
    v) Sketch an energy level diagram for the reaction.(2mks)
    b) Use the reduction potentials given below to explain why a solution
    containing copper ions should not be stored in a container made of zinc.
    Zn2+(aq) + 2e Zn(s); Eø = -0.76v
    Cu2+(aq) + 2e Cu(s); Eø = +0.34v (2mks)
  2. a) Distinguish between isotopes and allotropes. (2mks)
    b) The chart below is part of the periodic table. Study it and answer the questions that follow.(The letters are not the actual symbols of the elements).

i) Select the element in period three which has the shortest atomic radius. Give a reason for you answer. (2mks)
ii) Element F has the electronic structure, 2.8.18.4 on the chart above, indicate the position of element F. (1mks)
iii) State one use of the elements of which E is a member. (1mk)
iv) Write an equation to show the action of heat on the nitrate of element C.
(1mks)
c) When 3 litres of chlorine gas were completely reacted with element D, 11.875g
of the product were formed.Dertermine the relative atomic mass of element D.
(Atomic mass of chlorine = 35.5; molar gas volume = 24litres).(3mks)

  1. a) The diagram below shows some processes that take place during
    the industrial manufacture of sulphuric acid.

(i) Write the equation for the reaction in which sulphur dioxide gas is produced. (1mk)

(ii) Why is it necessary to keep the gases pure and dry ? (1mk)
(iii) Describe the process that takes place in chamber G. (1mk)
(iv) Name the gases that escape into the environment. (1mk)
(v) State and explain the harmful effect on the environment of one of the gases named in (iv) above (1mk)
(vi) Give one reason why it is necessary to use a pressure of 2-3 atmoshperes and not more. (1mk)
b) (i) Complete the table below to show the observations made when
concentrated sulphuric acid is added to the substances shown. (2mks)

Substance Observation
Iron fillings
Crystals of white sugar

(ii) Give reasons for the observations made using:
I iron fillings (1mk)
II Crystals of white sugar. (1mk)
(c) Name one fertilizer made from sulphuric acid. (1mk)
(d) Suggest a reason why BaSO4(apigment made from sulphuric acid) would be suitable in making paint for cars. (1mk)

  1. a) What name is given to a compound that contains carbon and hydrogen only? ( ½)
    b) Hexane is a compound containing carbon and hydrogen.
    (i) What method is used to obtain hexane from crude oil? (1mk)
    (ii) State one use of hexane (1mk)
    c) Study the flow chart below and answer the questions that follow. (i) Identify reagent L. (1mk) (ii) Name the catalyst used in step 5. (1mk) (iii) Draw the structural formula of gas J. (1mk) (iv) What name is given to the process that takes place in step 5? (½mk) d) (i) write the equation for the reaction between aqueous sodium hydroxide and aqueous ethanoic acid. (1mk)
    (ii) Explain why the reaction between 1g of sodium carbonate and 2M hydrochloric acid is faster than the reaction between 1g of sodium carbonate and 2M ethanoic acid. (1mks)
  2. The extraction of iron from its ores takes place in the blast furnace. Study it and answer
    the questions that follow.

a) Name
(i) One of the substances in the slag (1mk)
(ii) Another iron ore material used in the blast furnance. (1mk)
(iii) One gas which is recycled. (1mk)
b) Describe the process which leacd to the formation of iron in the blast furnace
c) State the purpose of limestone in the blast furnace. (3mks)
d) Give a reason why the melting point of the iron obtained from the blast furnace is 12000 C while tat of pure iron is 15350C (1mk)
(e) State two uses of steel (2mks)

  1. The table below shows the volumes of nitrogen dioxide gas produced when different volume of IM nitric acid were each reacted with 2.07 g of lead at room temperature.
    Volume of 1 M nitric acid (cm3) Volume of nitrogen dioxide gas (cm3)
    5 60
    15 180
    25 300
    35 420
    45 480
    55 480
    a) Give a reason why nitric acid is not used to prepare hydrogen gas. (1mk)
    b) Explain how the rate of the reaction between lead and nitric acid would be affected if the temperature of the reaction mixture was raised. (2mks)
    c) On the grid provided below, plot a graph of the volume of the gas produced (Vertical axis) against volume of acid. (3 marks)
    d) Using the graph, determine the volume of:
    i) Nitrogen dioxide produced when 30cm3 of 1 M nitric acid were reacted with 2.07 g of lead (1mrk)
    ii) 1M nitric acid which would react completely with 2.07g of lead. (1mk)
    e) Using the answer in d(i) above, determine:
    i) The volume of 1M nitric acid that would react completely with one mole of lead (pb=207) (2mks)
    ii) The volume of nitrogen dioxide gas produced when one mole of lead reacts with excess 1 M nitric room temperature. (1mk)
    f) Calculate the number of moles of:
    i) 1M nitric acid that reacted with one mole of lead (1mk)
    ii) nitrogen dioxide produced when one mole of lead were reacted with excess nitric acid. (Molar gas volume of 2400cm3) (1mk)
    g) Using the answers obtained in f (i) and (ii) above, write the equation for the reaction between lead and nitric acid given that one mole of lead nitrate and two moles of water were also produced. (1mk)

CHEMISTRY
PAPER 1
THEORY
OCT./NOV. 2007
2 hours

  1. The diagram below shows a “Jiko” when in use. Study it and answer the
    questions that follow.

a) Identify the gas formed at region A. (1mk)
……………………………………………………………………….
b) State and explain the observation made at region B. (2mks)
……………………………………………………………………….
………………………………………………………………………..

  1. 15.0cm3 of ethanoic acid (CH3COOH) was dissolved in water to make 500cm3 of solution. Calculate the concentration of the solution in moles per litre.
    (C=12.0;H=1.0;O=16.0; density of ethanoic acid is 1.05 g/cm3) (3mks)
    ……………………………………………………………………………………..
    …………………………………………………………………………………….
    …………………………………………………………………………………….
  2. Both chlorine and iodine are halogens.
    a) What are halogens? (1mk)
    ……………………………………………………………………………
    b) In terms of structure and bonding, explain why the boiling point of chlorine is lower than that of iodine. (2mks)
    ………………………………………………………………………
  3. The diagram below shows a Bunsen burner when in use. Name the regions labeled C and D. (2mks)
    C …………………………………………………………………………..
    D ………………………………………………………………………….
  4. When a student was stung by a nettle plant, a teacher applied an aqueous solution
    of ammonia to the affected area of the skin and the student was relieved of pain .Explain. (2mks)
    ………………………………………………………………………………………….
    ……………………………………………………………………………………………
    ……………………………………………………………………………………………
  5. In an experiment, a few drops of concentrated nitric acid were added to aqueous iron(II) sulphate in a test – tube. Excess sodium hydroxide solution was then added to the mixture.
    a) State the observations that were made when:
    i) Concentrated nitric acid was added to aqueous iron (II) sulphate(1mk)
    ……………………………………………………………………………
    ii) Excess sodium hydroxide was added to the mixture. (1mk)
    ……………………………………………………………………………
    b) Write and ionic equation for the reaction which occurred in (a) (ii) above.(1mk)
    …………………………………………………………………………………..
  6. a) Use the information given below to draw a labeled diagram of an
    electrochemical cell that can be constructed to measure the electromotive force between G and J.
    G2+(aq) + 2e G(s) ; E = – 0.74 V
    J2+(aq)+ 2e J(s); E = -0.14 V
    b) Calculate the E value for the cell constructed in (a) above. (1mk)
    ……………………………………………………………………
    ……………………………………………………………………
  7. Explain why there is general increase in the first ionization energies of the
    elements in period 3 of the periodic table from left to right. (2mks)
  8. Study the flow chart below and answer the question that follows.

Identify: (3mks)
a) Solution K
b) Solid L
c) Gas M
The thermo chemical equations for the formation of hydrogen peroxide under standard conditions are:
H2(g) +O2(g) H2O2(g); ∆Hθf = -133kJmol-1
H2(g) +O2(g) H20(l);∆Hθ=-188 kJmol -1

Write the thermo chemical equation for the molar heat of vaporization of hydrogen peroxide. (2mks)
The set-up below was used to collect a dry sample of a gas.

Give two reasons why the set-up cannot be used to collect carbon (IV) oxide gas. (2mks)

  1. a) State the Charles law (1mk)
    b) The volume of a sample of nitrogen gas at a temperature of 291 K and 1.0×105
    Pascal’s was 3.5 x 10-2m3. Calculate the temperature at which the volume of the gas would be 2.8 x 10-2m3 at 1.0 x 105 Pascal. (2mks)
  2. a) name the process that takes place when:
    (i) Crystals of zinc nitrate change into solution when exposed to air (1mk)
    (ii) An alcohol reacts with an organic acid in the presence of a catalyst to form a sweet smelling compound. (1mk)

b) Propane can be changed into methane and ethane as shown in the equation below;

CH3CH2CH3(g) High temperature CH4(g) + C2H4(g) (1mk)
Name the process undergone by propane. (1mk)

  1. a) Distinguish between nuclear fission and nuclear fusion. (2mks) Describe how solid wastes containing radioactive substances should be disposed of. (1mk)
  2. a) Explain why permanent hardness in water cannot be removed by boiling.(2mks)
    b) Name two methods that can be used to remove permanent hardness from water.
    (1mk)
    16 The table below shows the tests that were carried out on solid N and the observations made.
    I Test Observations
    II Dilute hydrochloric acid was added to solid N. A colourless solution was formed.
    III To the colourless solution obtained in test II, excess sodium hydroxide solution was added. A white precipitate was formed which dissolved to form a colourless solution.
    Write the formula of the anion in;
    a) Solid N (1mk)
    b) The colourless solution formed in test III (1mk)
  3. The relative formula mass of a hydrocarbon is 58. Draw and name two possible structures of the hydrocarbon (C=12.0; H=1.0) (3mks)
  4. starting with sodium metal, describe how a sample of crystals of sodium hydrogen carbonate may be prepared. (3mks)
    19 The flow chart below shows steps used in the extraction of zinc from one of its ores.

a) Name the process that is used in step 2 to concentrate the ore. (1mk)

b) Write an equation for the reaction which takes place in step 3. (1 mark)

c) Name one use of zinc other than galvanizing. (1mk)

An alcohol has the following composition by mass: hydrogen 13.5%, oxygen 21.6% and carbon 64.9%
Determine the empirical formula of the alcohol(C=12.0; H=1.0’)=16.0).

(2mks)

  1. a) When brine is electrolyzed using inert electrodes, chlorine gas is liberated at the anode instead of oxygen. Explain this observation. (2mks)
    b) Name the product formed at the cathode. (1 mk)
  2. 6.84g of aluminium sulphate were dissolve in 150cm3 of water. Calculate the molar concentration of the sulphate ions in the solution. (Relative formula mass of aluminium sulphate is 342)
    ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  3. The table below shows the relative molecular masses and the boiling points of pentane and propan-1-01
    Relative molecular mass Boiling point(oC)
    Pentane 72 36
    Propan-10-1 60 97

Explain why the boiling point of propane 1-1-01 is higher than that of pentane. (2mks)

  1. State and explain the observations made when excess ammonia gas reacts with chlorine
    gas (3mks)
  2. The diagram below shows a student’s set-up for the preparation and collection of hydrogen gas.

(a) How would the final volume of hydrogen gas produced be affected if 80cm3 of 0,75
M hydrochloric acid was used? (1mk)
(b) Give a reason why helium is increasingly being preferred to hydrogen in weather
balloons.

The table below shows the number of valence electrons of the element P, Q and R.

Element P Q R
Number of valence electrons 3 5 2
Explain why p and R would not be expected to form a compound. (1mk)
Write an equation to show the effect of heat on the carbonate of R (1mk)
Write the formula for the most stable ion or q. (1mk)

  1. The diagram below formula for the most stable ion of Q. (1mk)

On the same axis, sketch the graph for the decomposition of hydrogen peroxide when manganese (IV) oxide is added. (2mks)

  1. During the electrolysis of aqueous silver nitrate, a current of 5.0a was passed through the electrolysis for 3 hours.
    a) Write the equation for reaction which took place at the anode. (1mk)
    b) Calculate the mass of silver deposited (Ag = 108; IF=96500C) (2mks)
    29 The diagram below is a section of a model of the structure of element T.

a) State the type of bonding that exists in T. (1mk)
b) In which group of the period table does element T belong? Give a reason. (2mks)

  1. Below is a sketch of a graph showing the change in viscosity? (Ease of flow) with temperature when solid sulphur is heated.

Describe what happens to the sulphur molecules when sulphur is heated from 1500C to about 2000C.

CHEMISTRY
Paper 2
THEORY Oct/Nov. 2007

  1. (a) State two factors that should be considered when choosing fuel for cooking (2mks)
    (b) The diagram below represents a set – up that was used to determine the molar heat of
    combustion of ethanol

During the experiment, the data given below was recorded

Volume of water 450cm3
Initial temperature of water 250 C
Final temperature of water 46.50C
Mass of ethanol + Lamp before burning 125.5g
Mass of ethanol + lamp after burning 124.0g

Calculate the:
(i) Heat evolved during the experiment (density of water = 1g/cm3
    Specific heat capacity of water = 4.2 Jg-1K-1               ( 3 mks)

(ii)    Molar heat  of combustion  of ethanol (C = 12.0, O = 16.0, H=1.0)   ( 2 mks)

(c) Write the equation for the complete combustion of ethanol ( 1mk)

(d) The value of the molar heat of combustion of ethanol obtained in (b) (ii) above is lower than the theoretical value. State two sources of error in the experiment. ( 2 mks)

  1. (a) Give the systematic names of the following compounds (i) CH2 = C – CH3 CH3 ( 1 mk) (ii) CH3CH2CH2C ≡CH ( 1mk) (b) State the observations made when Propan – I- ol reacts with:
    (i) Acidified potassium dichromate (VI) Solution ( 1mk) (ii) Sodium metal ( 1mk) (c) Ethanol obtained from glucose can be converted to ethane as shown below

C6H12O6 C2H5OH CH2 ≡ CH2

    Name and describe the process that take place in steps I and II
    Step I                                  (1 ½ mks)

    Step II                                 ( 1 ½ mks)

(d) Compounds A and B have the same molecular formula C3H6O2. Compound A liberates carbon (IV) oxide on addition of aqueous sodium carbonate while compound B does not. Compound B has a sweet smell. Draw the possible structures of:
(i) Compound A ( 1 mark)

(ii) Compound B                         ( 1 mk)

(e) Give two reasons why the disposal of polymers such as polychloroethane by burning pollutes the environment. ( 2 mks)

  1. The flow chart below shows a sequence of chemical reactions starting with copper study it and answer the questions that follow.

(a) In step 1, excess 3M nitric acid was added to 0.5g of copper powder
(i) State two observations which were made when the reactions was in progress (2mks)

(ii) Explain why dilute hydrochloric acid cannot be used in step 1          ( 1mk)

(iii)    I  Write the equation for the reaction that took place in step 1   (1mk)

II Calculate the volume of 3M nitric that was needed to react completely with 0.5g of copper powder. (Cu = 63.5) ( 3 mk)

(b) Give the names of the types of reactions that  took  place  in steps 4  and 5   ( 1 mk)
    Step 4
    Step 5

(c) Apart from the good conductivity of electricity, state two other properties that make it possible for copper to be extensively used in the electrical industry. 2mks)

  1. (a) Methanol is manufactured from carbon (IV) oxide and hydrogen gas according to
    the equation: CO2(g) + 3H2¬(g) CH3OH(g) + H2O(g)
    The reaction is carried out in the presence of a chromium catalyst at 700K and 30kPa. Under these conditions, equilibrium is reacted when 2% of the carbon (IV) oxide is converted to methanol

(i) How does the rate of the forward reaction compare with that of the reverse reaction when 2% of the carbon (IV) oxide is converted to methanol? ( 1 mk)

(ii) Explain how each of the following would affect the yield of methanol:
I Reduction (2mks)

II  Using a more  efficient catalyst                    (2mks)

(iii) If the reaction is carried out at 500K and 30kPa, the percentage of carbon (IV) oxide converted to methanol is higher than 2%

I what is the sign of ∆H for the reaction? Give a reason            (2mks)

II Explain why in practice the reaction is carried out at 700K but NOT at 500K
                                        (1mk)

(b) Hydrogen peroxide decomposes according to the following equation:
2H2O2(aq) →2H2O(l) + O2 (g)
In an experiment, the rate of decomposition of hydrogen peroxide was found to be 6.0 x 10-8 mol dm-3 S-1.

(i) Calculate the number of moles per dm3 of hydrogen peroxide that had decomposed within the first 2 minutes (2mks)

(ii) In another experiment, the rate of decomposition was found to be 1.8 x 10-7 mol dm-3S-1. The difference in two rates could have been caused by addition of a catalyst. State, giving reasons, one other factor that may have caused the difference in two rates of decomposition (2mks)

  1. (a) The diagram below represents part of the structure of a sodium chloride crystal.
    The position of one of the sodium ions in the crystal is shown as  (i) On the diagram, mark the position of the other three sodium ions ( 2 mks)
    (ii) The melting and boiling points of sodium chloride are 8010C and 14130C
    respectively.
    Explain why sodium chloride does not conduct electricity at 250C, but does so at
    temperatures between 8010 C and 14130C ( 2 mks)
    (b) Give a reason why ammonia gas is highly soluble in water ( 2mks)
    (c) The structure of an ammonia ion is shown below: Name the type of bond represented in the diagram by N → H ( 1 mark)

(d) Carbon exists in different crystalline forms. Some of these forms were recently discovered in soot and are called fullerenes

(i) What name is given to different crystalline forms of the  same element?
                                    (1mk)
(ii)    Fullerenes dissolve in methylbenzene while the other forms of carbon do 

not.
Given that soot is a mixture of fullerenes and other solid forms of carbon, describe how crystals of fullerenes can be obtained from soot. ( 3mks)

(iii) The relative molecular mass of one of the fullerenes is 720. What is the molecular formula of this fullerene? (C=12.00 ( 1 mk)

  1. (a) The elements nitrogen, phosphorous and potassium are essential for plant
    growth.
    (i) Potassium in fertilizers may be in the form of potassium nitrate
    Describe how a sample of a fertilizer may be tested to find out if it contained nitrate ions. (2mks)

(ii) Calculate the mass of nitrogen present if a 25kg bag contained pure ammonium phosphate, (NH4)2 HPO4. (N = 14.0, H=1.0, P = 31.0, O = 16.0
(2mks)
(b) The table below shows the solubility of ammonium phosphate in water at different temperatures.
Temperature
(C0) Solubility of ammonium phosphate in g/100g water

10 63.0
20 69.0
30 75.0
40 82.0
50 89.0
60 97.0

(i) On the grid provided, draw the solubility curve of ammonium phosphate
(Temperature on x – axis) (3 mks)
(ii) Using the graph, determine the solubility of ammonium phosphate at 250C ( 1 mk)

(iii) 100g of a saturated solution of ammonium phosphate was prepared at 250C
I what is meant by a saturated solution? ( 1mk)
II Calculate the mass of ammonium phosphate which was used to prepare the saturated solution ( 2 mks)

(c) The graph below shows how the PH value of soil in a farm changed over a period of
time

(i) Describe how the pH of the soil can be determined (2mks)

(ii) State one factor that may have been responsible for the change in the soil pH in
the time interval AB ( 1 mk)

  1. The diagram below shows the set up used in an experiment to prepare chlorine gas and react it with aluminium foil. Study it and answer the question that follow

(a) In the experiment, concentrated hydrochloric acid and potassium manganate (VII) were used to prepare chlorine gas. State two precautions that should be taken in carrying out this experiment. (2mks)

(b) Write the formula of another compound that could be used instead of potassium manganate (VII) ( 1 mk)
(c) Explain why it is necessary to allow the acid to drip slowly onto potassium manganate (VII) before the aluminium foil is heated. ( 2 mks)

(d) State the property of the product formed in the combustion tube that makes it possible for it to be collected in the receiver ( 1mk)

(e) When 1.08g of aluminum foil were heated in a stream of chlorine gas, the mass of the product formed was 3.47 g
Calculate the:
(i) Maximum mass of the product formed if chlorine was in excess;
(Al= 27; Cl = 35.5)
(ii) Percentage yield of the product formed ( 1 mk)

(f) Phosphorous trichloride is a liquid at room temperature. What modification should be made to set up if it is to be used to prepare phosphorous trichloride? ( 1 mk)

CHEMISTRY THEORY PAPER 1
OCT/NOV. 2008
2 HOURS

  1. A small crystal of potassium manganate (VII) was placed in a beaker water. The beaker was left standing for two days without shaking. State and explain the observations that were made. 2mks)
  2. When a hydrated sample of calcium sulphate CaSO4 XH2O was heated until all the water was lost, the following data recorded;
    Mass of crucible = 30.296 g
    Mass of crucible +hydrated salt = 33.111 g
    Mass of crucible + anhydrous salt = 32.781 g
    Determine the empirical formula of the hydrated salt (Relative formula mass of CaSO4 =136, H2O =18). (3mks)
  3. Complete the following table by filling in the missing test and observations
    (3mks)
    No. Gas Test Observation
    I Chlorine Put a moist red litmus paper into the gas
    II Sulphure (IV) oxide Paper turns green

III Butane Add a drop of bromine water

  1. The structure of a detergent is H H H H H H H H H H H H H H- C- C- C- C- C- C- C- C- C- C -C- C- -C- COO-Na-1 H H H H H H H H H H H H H

a) Write the molecular formula of the detergent. (1mk)
b) What type of detergent is represented by the formula? (1mk)
c) When this type of detergent is used to wash linen in hard water, spots (marks) are left on the linen. Write the formula of the substance responsible for the spots (1mk)

  1. Phosphoric acid is manufactured from calcium phosphate according to the following equation.
    Ca3(PO4)2(s) + 3H2SOv(l) 2H3PO4(AQ) + 3 CaSO4(S)

Calculate the mass in (Kg) of phosphoric acid that would be obtained if 155 Kg of calcium phosphate reacted completely with the acid
(Ca=40, P=31, S=32, O=16, H=1) (2mks)

  1. The structure below represents a sweet smelling compound
    O CH3 CH2 CH2 C O CH2 CH 2 CH3.
    Give the names of the two organic compounds that can be used to prepare this compound in the laboratory. (2mks)
  2. a) What are isotopes? (1mk)
    b) Determine the number of neutrons in 18
    O.
    8 (1mk)
  3. a) State the observation made at the end of the experiment when a mixture of
    iron powder and sulphur is heated in a test tube. (1mk)
    b) Write an equation for the reaction the product in (a) above and dilute hydrochloric acid. (1mk)
    c) When a mixture of iron powder and sulphur is heated, it glows more brightly than that of iron fillings and sulphur. Explain this observation
    (1mk)
  4. Zinc reacts with both concentrated and dilute sulphuric (VI) acid. Write equations for two reactions. (2mk)
  5. When magnesium was burnt in air, a solid mixture was formed. On addition of water to the mixture a gas which turned moist red litmus paper blue was evolved. Explain these observations.
  6. The table below gives atomic numbers of elements represented b the letters a, B, C and D.

Element A B C D
Atomic number 15 16 17 20

Use the information to answer the questions that follow.
a) Name the type of bonding that exists in the compound formed when A and D react (1mk)
b) Select the letter which represents the best oxidizing agent. Give a reason for your answer. (2mks)

  1. In an experiment, a test-tube full of chlorine water was inverted in chlorine water as shown in the diagram below and the set up left in sunlight for one day.

After one day, a gas was found to have collected in the test-tube
a) Identify the gas.
b) What will happen to the PH of the solution in the beaker after one day? Give an explanation. (2mks)

  1. In a laboratory experiment hydrogen gas was passed over heated copper (II) oxide as shown the diagram below. Describe a chemical test that can be used to identify the product e. (2mks)
  2. Samples of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2.
    A chromatogram was run using methanol. The figure below shows the chromatogram.

a) Identify the athlete who had used an illegal drug. (1mk)
b) Which drug is more soluble in methanol? (1mk)

  1. The table below gives the solubilities of substances J, K and L at different temperatures

Substance Solubility in grammes per 100 g water at
00C 200C 400C 600C
J
K
L 0.334
27.60
35.70 0.16
34.0
36.0 0.097
40.0
40.0 0.0058
45.5
37.3
Select the substance which, when dissolved in water, heat is given out. Give a reason .(2mks)

  1. Starting with copper metal, describe how a sample of crystals of copper (II) chloride may be prepared in the laboratory. (3mks)
  2. A compound whose general formula is M (OH)3 reacts as shown by the equation below.
    M (OH) 3(s) + OH (aq) M (OH) 4(aq) M (OH) 3(s) + 3H+ (aq) M3+ (aq) + 3H2O (i)

(a) What name is given to compounds which behave like M (OH) 3 in the two
Reactions (1 mk)
(b) Name two elements whose hydroxides behave like that of M (2 mks)

  1. The grid below is part of the periodic table. Use it to answer the questions that follow, (the letters are not the actual symbols of the elements).

a) Indicate on the grid the position of an element represented by letter V whose atomic number is 14. (1mk)
b) Select a letter which reaction between Q and T. (1mk)

  1. Select a letter which represents a mono atomic gas. (1mk) Zn1+(aq) + 2e- Zn(s) -0.76
    Pb2+(aq) +2e- Pb(s) -0.13
    Ag+ (aq) +e- Ag(s) +0.80
    Cu2+(aq) + 2e- Cu(s) +0.30
    a) Write the cell representation for the electrochemical cell that would give the highest E (1mk)
    b) State and explain the observations made when a copper rod is placed in a beaker containing silver nitrate solution. (2mks)
  2. a) State the Graham’s law diffusion. (1mk)
    b) The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through a porous material is 12cm3s-1 calculate the rate of diffusion of X through the same material. (2mks)
  3. The diagram below represents an experiment that was set up to investigate movement of ions during electrolysis. When the circuit was completed, it was noticed that a blue colour spread towards the right.
    a) Explain this observation (2mks)
    b) Write the equation for the reaction that occurred at the anode. (1mk)
  4. The diagram below is part of a set up used in the laboratory preparation of a gas.

Complete the diagram to show how a dry sample of the gas can be collected.
(3mks)

  1. In a closed system, aqueous iron (III) chloride reacts with sulphide gas as shown in the equation below.
    2FeCl3(aq) + H2S(g) 2FeCl2(aq) 2HCl(aq) + S(s)
    State and explain the observation that would be made if dilute hydrochloric acid is
    added to the system at equilibrium. (2mks)
  2. a) A radioactive substance emits three different particles.
    Give the symbol of the particle with the highest mass. (1mk)
    b) (i) Find the values of Z1 and Z2 in the nuclear equation below
    Z1 1 94 140 1
    U + n Sr + xe +2 n
    92 0 38 Z0 0
    iii) What type of nuclear reaction is represented in represented in b (i) above?
    (1mk) Time (minutes) Give the name of the:
    a) Process taking place between t0 and t1. (1mk)
    b) Energy change that occurs between t3 and t4
  3. When solid B1 was heated, a gas which formed a white precipitate when passed through lime water was produced. The residue was dissolved in dilute nitric (V) acid to form a colourless solution B2. when dilute hydrochloric acid was added to solution B2 a white precipitate which dissolved on warning was formed.
    a) Write the formula of the;
    I Cation in solid B1 (1mk)
    II anion in solid B1 (1mk)
    b) Write an ionic equation for the reaction between the resdue and dilute nitric (V) acid. (1mk)
  4. In an experiment to determine the percentage of magnesium hydroxide in an anti-acid, a solution containing 0.50 g of the anti-acid was neutralized by 23.0 cm3 of 0.010m hydrochloric acid (Relative formula mass of magnesium hydroxide =58)
    a) Mass of magnesium hydroxide in the anti-acid; (2mks)
    b) Percentage of magnesium hydroxide in the anti-acid (1mk)
  5. During the extraction of aluminium from its ores; the ore is first purified to obtain alumina.

a) Name
(i) Substance C1 (1mk)
………………………………………………………………………..
(ii) Process D1 (1mk)
…………………………………………………………………………
b) Give two reasons why aluminium is used extensively in the making of cooking pans. (1mk)

  1. A certain mass of a metal E1 reacted with excess dilute hydrochloric acid at 25oC. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were presented as shown in the graph below.
    a) Name one piece of apparatus that may have been used to measure the volume of gas liberated. (1mk)

b) (i) On the same axis, sketch the curve that would be obtained if the experiment was repeated at 350C. (1mk)

    (ii)    Explain the shape of your curve in b(i) above.  (1mk)
  1. Crude oil contains sulphur. What would be the effect to the environment of using fuel containing sulphur? (1mk)
  2. Study the flow chart below and answer the questions that follow. a) Give the name of the process that takes place in step 1. (1mk)
    b) Give;
    (i) The name of substance G1
    (ii) One use of substance F1

CHEMISTRY PAPER 2 THEORY
OCT /NOV. 2008
233/2
2 HOURS

  1. a) Biogas is a mixture of mainly carbon (IV) oxide and methane.
    (i) Give a reason why biogas can be used as a fuel. (1mk)
    (ii) Other than fractional distillation, describe a method that can be
    used to determine the percentage of methane in biogas. (3mks)

b) A sample of biogas contains 35.2% by mass of methane. A biogas cylinder contains 5.0 kg of the gas.
Calculate the;
(i) Number of moles of methane in the cylinder. (Molar mass of methane=16)
(2mks)
(ii) Total volume of carbon (IV) oxide produced by the combustion of methane in the cylinder (Molar gas Volume=24.0 dm-3+ at room temperature and pressure). (2mks)

c) Carbon (Iv) oxide, methane, nitrogen (I) oxide and trichlorofluoromethane are green-house gases.
(i) State one effect of an increased level of these gases to the environment. (1mk)
(ii) Give one source from which each of the following gases is released to the environment;
I Nitrogen (i) oxide (I mk)
II Trichlorofluoromethane. (1mk)

2 a) Write an equation to show the effect of heat on the nitrate of:
(i) Potassium (1mk)
b) The table below gives information about elements A1A2A3, and A4
Element Atomic
Number Atomic
Radius (nm) Ionic radius (nm)
A1
A2
A3
A4 3
5
13
17 0.134
0.090
0.143
0.099 0.074
0.012
0.050
0.181

(i) In which period of the periodic table is element A2? Give a reason
(2 mks)
(ii) Explain why the atomic radius of:
I A1 is greater than that of A2;
II A4 is smaller than its ionic radius (2 mks)
(iii) Select the element which s in the same group as A3 (1 mk)
(iv) Using dots (.) and crosses(x) to represent outermost electrons. Draw a
diagram to show the bonding in the compound formed when A1 reacts with A4 (1 mk)

  1. (a) Describe the process by which Nitrogen is obtained from air on a large scale.
    (4 mks)
    (b) Study the flow chart below and answer the questions that follow.

(i) Identify gas J. (1 mk)
(ii) Using oxidation numbers, show that ammonia is the reducing agent in step (VI) (2mks)
(iii) Write the equation for the reaction that occurs in step (V). (1mk)
(iv) Give one use of ammonium nitrate. (1mk)

c) The table below shows the observations made when aqueous ammonia was added to cations of elements F2F and G until in excess.

Cation of
Addition of a few drops of
Aqueous ammonia. Addition of excess aqueous ammonia.
E White precipitate Insoluble
F No precipitate No precipitate
G White precipitate Dissolves

(i) Select the cation that is likely to be Zn2+             (1mk)

(ii) Given that the formula of the cation of element E is E 2+, write the ionic equation for the reaction between E2+ (aq) and aqueous ammonia. (1mk)

4a) (i) State the Le chatelier’s principle. (1mk)
(ii) Carbon (II) oxide gas reacts with steam according to the equation;
CO(g) + H2O(g) H2(g)+ CO+2(g)
What would be the effect of increasing the pressure of the system at equilibrium? Explain. (2mks)

b) The table below gives the volumes of oxygen gas produced at different times when hydrogen peroxide decomposed in the presence of a catalyst.

Time(Sec) 0 10 20 30 40 50 60
Volume of oxygen (cm3) 0 66 98 110 119 120 120

(i) Name the catalyst used for this reaction                (1mk)

(ii) On the grid provided, draw the graph of volume of oxygen gas produced (vertical axis) against time. (3mks)
(iii) Using the graph, determine the rate of decomposition of hydrogen peroxide after 24 seconds. (2mks)
(iv) Give a reason why the total volume of oxygen gas produced after 50 seconds remains constant. (1mk)

  1. (a) Alkanes, alkenes and alkynes can be obtained from crude oil. Draw the
    structure of the second member of the alkyne homologous series. (1mk) Study the flow chart below and answer the questions that follow State the conditions for the reaction in step 1 to occur ( 1 mk)
    Identify substance II ( 1 mk)
    Give:
    I. One advantage of the continued use of substance such as J (1 mk)
    II The name of the process that takes place in step III (1 mk)
    III The name and the formula of substance K (2mks)

Name:………………………………

Formula:……………………………
The relative molecular mass of J is 16,800. Calculate the number of monomers that make up J.

The table below  give the formula  of  four  compounds L,M,N and  P

Compound Formula
L C2H6O
M C3H6
N C3H6O2
P C3H8
Giving a reason in each case, select the letter which represents a compound that:
(i) Decolorizes bromine in the absence of UV light ( 2 mks)
(ii) Gives effervescence when reacted with aqueous sodium carbonate
( 2 mks)

The diagram below represents a set up that can be used to electrolyze aqueous copper (II) sulphate.

(a) (i) Describe how oxygen gas is produced during the electrolysis ( 2 mks)
(ii) Explain why copper electrodes are not suitable for this electrolysis
( 2 mks)
Impure copper is purified by an electrolytic process
(i) Name one ore from which copper is obtained ( 1 mk)
(ii) Write the equation for the reaction that occur at the cathode during the
purification of copper ( 1 mk)
(iii) In an experiment to electroplate a copper spoon with silver, a current of 0.5 A was passed for 18 minutes. Calculate the amount of silver deposited on the spoon (π = 96500 coulombs, Ag = 108) (3mks)
Give two reasons why some metals are electroplated (2mks)

  1. (a) Define the standard enthalpy of formation of a substance ( 1 mk)
    (b) Use the thermo chemical equations below to answer the questions that
    follow. C2H6(g) + 7/2 O2(g) →2Co2(g) + 3H2o (i); ∆ H1 – 1560kjmol-1 C(graphite) + O2 (g) →Co2(g); ∆H2 = -394kJmol-1 H2(g) + ½ O2 (g) → H2o(g) ∆H3 = -286kJmol¬-1

(i) Name two types of heat changes represented by ∆H3 ( 2 mks)
(ii) Draw an energy level diagram for the reaction represented by equation 1
(iii) Calculate the standard enthalpy of formation of ethane ( 2 mks)
When a sample of ethane was burnt, the heat produced raised the temperature of 500g of water by 21. 5 K, (specific heat capacity of water = 4.2Jg-1K).
Calculate the:
Heat change for the reaction ( 2 mks)
Mass of ethane was burnt. ( relative formula mass of ethane= 30)
( 2 mks)

CHEMISTRY 2009
PAPER 1

  1. The ionization energies for three elements A. B and C are shown in the table below:

Element A B C
Ionisation energy (kJ/mole) 519 418 494

a) what is meant by ionization energy? (1 mk)
b) which element is the strongest reducing agent? Give a reason. (2 mks)

  1. Hardness of water may be removed by either boiling or addition of chemicals
    a) write an equation to show how boiling removes hardness of water. (1 mk)
    b) name two chemicals that are used to remove hardness of water. (2 mks)
  2. The atomic number of sulphur is 16.
    Write the electron arrangement of sulphur in the following: (2 mks) a) H2s; b) SO23
  3. An experiment was set up as shown in the diagram below: a) Identify substance D. (1 mk)

b) Describe how the other product of the burning candle could be prevented from getting into the environment. (2 mks)

  1. In terms of structure and bonding, explain why the melting point of oxygen is much
    lower than that of sodium. (3 mks)
  2. An isotope of element E has 34 neutrons and its mass number is 64. E forms a cation with 28 electrons. Write the formula of the cation with 28 electrons. Write the formula of the cation indicating the mass and atomic numbers. (1mk)
  3. When aluminium oxide was electrolysed, 1800kg of aluminium metal were obtained.
    a) Write equation for the formation of aluminium metal (1 mk)
    b) Calculate the quantity of electricity in faradays used (Al=27) (2 mks)
  4. Using dots (.) and crosses (x) , show bonding in: a) The compound formed when nitrogen reacts with fluorine
    (Atomic numbers F=9, N=7); (1mk) b) Sodium oxide.
    (Atomic numbers Na= 11, 0 = 8) (1 mk)
  5. a) what is meant by molar heat of solution? (1 mk) b) the lattice energy of sodium bromide and hydration energies of sodium and bromide ions are: 733,406 and 335 kJmol -1 respectively.
    i) Complete the energy cycle diagram below by inserting the values of
    H1, H2, and H3 (1 ½ mks) ii) Determine the molar heat of solution of solid sodium bromide. ( ½ mk)
  6. Hydrogen and oxygen can be obtained by electrolysis of acidified water.
    Using equations for the reactions at the electrodes, explain why the volume of hydrogen obtained is twice that of oxygen. (2mks)
  7. Starting with 50 cm3 of 2.8M sodium hydroxide, describe how a sample of pure sodium sulphate crystals can be prepared. (3 mks)
  8. The standard reduction potentials of two half –cells are: Ag+(aq) + e AG(s) ; E = 0.80V 2H2O (l) + 2e H2 (g) + 2OH (aq); E1 = 0.83V Draw a labelled diagram of an electro chemical cell that can be constructed using the two half –cells (3 mks)
  9. When 8.53 of sodium nitrate were heated in an open test-tube the mass of oxygen gas produced was 0.83 g . Given the equation of the reaction as 2NaNO3(s) 2NaNO2(s) + O2(g) Calculate the percentage of sodium nitrate that was converted to sodium nitrite (Na = 23.0 N = 14.0 O = 16.0) (3 mks)
  10. a) Draw and name the structure of the compound formed when one mole of
    ethyne reacts with one mole of hydrogen bromide. (2mks) b) Draw the structures of the alkynes whose molecular formula is C4H6 (1 mk)
  11. a student used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment was carried out for ten minutes a) What observation would be made if gas F is ignited? (1 mk) b) When the experiment was repeated using iron powder instead of magnesium
    ribbon very little gas F was obtained.

i) Give a reason for this observation (1 mk)

ii) What change in the conditions of the experiment should the student have made in order to increase the volume of gas F Produced? (1mk)

  1. The solubility curve of potassium nitrate is shown below.
    a) Determine the solubility of potassium nitrate at 500C (1 mk) b) Determine the molar concentration of saturated potassium nitrate at 500C
    (K=39.0 0= 16.0 N= 14.0 and density of water 1 g/cm3). (2 mks)
  2. The structure of methanoic acid is

What is the total number of electrons used for bonding in a molecule of methanoic acid? Give reasons. (2 mks)

  1. Bottles of sodium carbonate, sodium chloride and sugar have lost their labels.
    A student prepares and tests an aqueous solution of a sample from each bottle. The results obtained are as shown in the table below.

Bottle PH Electrical Conductivity Correct label
1 7 Conducts
2 7 Does not conduct
3 10 conducts

Complete the table by filling the correct label for each bottle. (3 mks)

19) The figure below represents the set up that was used to crack an alkane.

a)  What was the purpose of the sand?               (1 mk)

b)  After some time, a colourless gas G collected in the test-tube.

Describe a chemical test and the observations that would be made in ordered to identify the class of compounds to which gas G belongs. (2 mks)

  1. Classify the following processes as either chemical or physical. (3 mks)

Process Type of change
a) Heating copper (II) sulphate crystals
b) Obtaining kerosene from crude oil
c) Souring of milk

  1. Give the name of the product formed when magnesium reacts with phosphorus.
    (1 mk)
  2. a student added very dilute sulphuric (VI) acid to four substances and recorded the observations shown in the table below.

Test Substance Gas given off
1 Sodium Yes
2 Iron No
3 Carbon Yes
4 Copper No

For which tests are the observations wrong? Explain         (3 mks)
  1. Use the flow chart below to answer the questions that follow. a) What observation would be made in step I? (1 mk) b) Name another substance that could be used in step 2. (1 mk) c) Give the name of substance H. (1 mk)
  2. The boiling points of some compounds of hydrogen with some elements in groups 4 and 6 of the periodic table are given below.

Compound Boiling point (0C) Compound Boiling point(0C)
CH4 -1640 H2O 100.0
SIH4 -112.0 H2S -61.0

a)  Which of the compounds CH4 and SIH4 has stronger intermolecular forces?                                     (1 mk)

b)  Explain why the boiling points of H2¬O and H2S show different trends from 

that of CH4 and SIH4 (2mks)

  1. For each of the following reactions, state the observation and write the formula of the
    Compound responsible for the observation:
    a) Bromine water is added to aqueous potassium iodide; (1 ½ mks)

b) Excess aqueous ammonia is added to copper (II) hydroxide (precipitate).
(1 ½ mks)

  1. The graph below shows the relationship between pressure and the temperature of a
    gas in a fixed volume container. Pressure (Pa)
    Temperature (0C)
    a) State the relationship between pressure and temperature that can be deduced
    from the graph. (1 mk) b) Using kinetic theory, explain the relationship shown in the graph. (2 mks)
  2. The following reaction is in equilibrium in a closed container

C(s) + H2O(g) . CO(g) + H2(g)

State giving reasons how an increase in pressure would affect the amount of 

hydrogen. (2 mks)

  1. The energy level diagram below shows the effect of a catalyst on the reaction path. a) What does point M represent? (1 mk)

CHEMISTRY
PAPER 2

  1. a) Two reagents that can be used to prepare chlorine gas are manganese (IV)
    oxide and concentrated hydrochloric acid.
    i) Write an equation for the reaction. (1 mk)

ii) Give the formula of another reagent that can be reacted with
concentrated hydrochloric acid to produce chlorine gas. (1 mk)
iii) Describe how the chlorine gas could be dried in the laboratory (2mks)
b) In an experiment, dry chlorine gas was reacted with aluminium as shown in
figure 1.

i) Name substance A. (1 mk)

ii) Write an equation for the reaction that took place in the combustion tube. (1mk)

iii) 0.84 g of aluminium reacted completely with chlorine gas. Calculate the volume of chlorine gas used (Molar gas volume is 24dm3, al = 27).
(3 mks)

iv) Give two reasons why calcium oxide is used in the set up. (2 mks)
2 a) Draw the structures of the following compounds: (2 mks)
i) 2- methylbut -2 ene;
ii) heptanoic acid

b) Describe a physical test that can be used to distinguish between methanol and hexanol. (2 mks)

c) Use the flow chart below to answer the questions that follow.

i)  Name:

    (I) the type of reaction that occurs in step II;        (1 mk)

     (II)   Substance B.                        (1 mk)


ii) Give the formula of substance C.                (1 mk)

iii) Give the reagent and the conditions necessary for the reaction in step (IV) (3mks)
3 The set-up below (figure 2) was used to electrolyse a bromide of metal D DBr2.

i) Write equation for the reactions at the

    I    cathode                            (1 mk)

    II  anode                           (1mk)


ii) The electrodes used in the experiment were made of carbon    and metal D.
    which of the two electrodes was used as the anode? Give a reason.   (2 mks)


iii)    Give a reason why this experiment is carried out in a fume cupboard.

(1 mk)

iv) When a current of 0.4 A was passed for 90 minutes, 2.3 1 g of metal D were 

deposited.

I Describe how the amount of metal D deposited was determines.
(3 mks)
II Calculate the relative atomic mass of metal D. (I Faraday = 96500
coulombs) (3 mks)

  1. a) the schematic diagram shows part of the Solvay process used for the
    manufacture of sodium carbonate.

i) Explain how the sodium chloride required for this process is obtained
from sea water. (2 mks)

    ii) Two main reactions take place in UNIT I .  The first one is the 

formation of ammonium hydrogen carbonate.

I. Write an equation for this reaction (1 mk)

II. Write an equation for the second reaction (1 mk)
iii) State how the following are carried out: (2 mks)

        I   Process I
        II) Process II

iv)In an experiment to determine the percentage purity of the sample of sodium carbonate produced in the Solvay process, 2.15 g of the sample reacted completely with 40.0cm3 of 0.5 M sulphuric acid.

I   calculate the number of moles  of sodium carbonate that 

reacted. (2 mks)
II Determine the percentage of socium carbonate in the sample.
(Na= 23.0, C= 12.0, O = 16.0) (2 mks)

b)  Name two industrial uses of sodium carbonate        (2 mks)

have been identified and others labelled.

i) Give the names of the processes

I   H                       (1 mk)

II  G                       (1 mk)

ii) Name one substance that can undergo process F when left in an open
container in the laboratory. (1 mk)

iii)    The process J is called deposition.  Using water as an example, write 

an equation that represents the process of deposition. (1 mk)
b) Figure 4 shows the beating curve for water.

    i)  Give the names of the intermolecular forces of attraction in the 

segments;

I MN (1mk)
II RS (1 mk)

    ii) The heats of fusion and vaporization of water are 334.4 Jg-1  and 

1159.4 Jg-1 respectively.

I Explain why there is a big difference between the two.(2mks)
II How is the difference reflected in the curve? (1 mk)

c)  Coal, oil and natural gas are major sources of energy.  They are known as 

fossil fuels. Hydrogen is also a source of energy.
i) State and explain two reasons why hydrogen is a very attractive fuel
compared to fossils. (3 mks)

    ii) State one disadvantage of using hydrogen fuel instead of fossil fuels.
  1. a) Study the table below and complete it. (W-1 and X4+ are not the actual
    symbols of the ions). (2 mks)  
    Iron
    Number of protons Number of neutrons Mass
    Number Electron arrangement
    W …………….. 20 ……………. 2.8.8
    X4+ 14 …………… 28 ………….. b) State the observation that would be made in the following tests to distinguish between:
    i) Sodium and copper burning pieces of each in air. (2 mks) ii) Sodium and Magnesium by placing small pieces of each in cold water which contains two drops of phenolphalein. (2mks) c) The atomic numbers of Na and Mg are 11 and 12 respectively. Which of the elements has a higher ionization energy? Explain. (2mks) d) Naturally occurring uranium consists of three isotopes which are radioactive.
    Isotope 234 235 238
    U U U

Abundance 0.01% 0.72% 99.27%

i) Which of these isotopes has the longest half-life? Give a reason
(1 mk)
ii) Calculate the relative atomic mass of uranium (2mks)

iii) 235 Is alpha emitter. If the product of the decay of this
U
92 nuclide is thorium (Th) . Write a nuclear equation for the
process. (1mk)

  1. Iron is obtained from haematite using a blast furnace shown if figure 5 below. a) Four raw materials are required for the production of iron. Three of these are
    iron oxide, hot air and limestone
    Give the name of the fourth raw material (1 mk)
    b) Write an equation for the reaction in which carbon (IV) oxide is converted
    into carbon (II) oxide. (1mk) c) Explain why the temperature in the region marked Y is higher than that of the
    incoming hot air. (2 mks) d) State one physical property of molten slag other than density that allows it to
    be separated from molten iron as shown in figure 5. (1mk) e) One of the components of the waste gases is Nitrogen (IV) oxide
    describe the adverse effects it has on the environment. (2mks) f) Iron from the blast furnace contains about 5% carbon
    i) Describe how the carbon content is reduced. (2mks) ii) Why is it necessary to reduce the carbon content? (1 mk)

CHEMISTRY
PAPER ONE-2010

  1. (a) Distinguish between a deliquescent and a hygroscopic substance.(2 marks)
    (b) Give one use of hygroscopic substances in the laboratory. (1 mark)
  2. (a) What is meant by the terms: (2 marks)
    (i) element;
    (ii) atomic number?
    (b) The formula for a chloride of titanium is TiCl3. What is the formula of its sulphate? (1 mark)
  3. What is the name given to each of the following:
    (a) ability of a metal to be made into a wire; (1 mark)
    (b) minimum energy required for a chemical reaction to start; (1 mark)
    3
    (c) type of force that holds atoms of neon together? (1 mark)
  4. Draw the structures and give the names of three alkanes having molecular formula C5H10 (3 marks)
  5. Hydrated cobalt(JI) chloride exists as pink crystals and anhydrous cobalt (II) chloride is a blue powder. Describe a laboratory experiment that can be used to show that the action of heat on hydrated cobalt (II) chloride is a reversible reaction. (3 marks)
  6. Aluminium oxide reacts with both acids and bases.
    (a) Write an equation for the reaction between aluminium oxide and hydrochloric acid. (1 mark)
    (b) Using the equation in (a) above, calculate the number of moles of hydrochloric acid that would react completely with 153 .0g of aluminium oxide. (Al 27.0, 0 = 16.0). (2 marks)
  7. Complete the table below by writing the products formed at the electrodes during the
    electrolysis of the electrolytes given in the table. (3 marks)

Electrolyte Product at anode Product at cathode
Aqueous sodium sulphate using inert electrodes.

    (1/2 mark)


            ½ mark    
            (1/2 mark)


                ½ mark

Aqueous copper(II) sulphate using copper electrodes.

       (1mark)    
                (1mark)
  1. The pressure of nitrogen gas contained in a 1dm3 cylinder at -1960C was 107 Pascals. Calculate the:
    (a) volume of the gas at 250C and 105 Pascals; (1 1/2 marks) (b) mass of nitrogen gas (Molar volume of gas is 24dm3,N=14.0)
    (11/2 marks)
  2. Carbon -14, 14¦6C is used in carbon dating. It decays to form nitrogen, 14¦6N . The graph below shows the amount of carbon -14 left in a sample against its age in years.

(a) Write a nuclear equation for the decay process of carbon -14 (1 mark)

(b) From the graph, determine the:
(i) half-life of carbon -14;

(ii)    percentage of carbon -14 in a sample whose age is 1950 years.
        (1 mark)
  1. The figure below shows an energy cycle. (a) Give the name of the enthalpy change /XH1. (1 mark) (b) Determine the value of AH3. (2 marks)
  2. Hydrogen sulphide is a highly toxic and flammable gas. It is normally prepared in a fume chamber. Name two reagents that can be used to prepare hydrogen sulphide in the laboratory. (1 mark) (b) One of the uses of hydrogen sulphide is to produce sulphur as shown in the
    following equation:
    2H2S + SO2(g) 2S(s) + 2H2O(1) Identify the reducing agent in this reaction and give a reason for your answer. (1 mark) Other than production of sulphuric (VI) acid, state one commercial use of sulphur. (1 mark)
  3. A beaker contained 75.0c3 of aqueous copper (II) sulphate at 23 .70C. When scrap
    iron metal was added to the solution, the temperature rose to 29.30C.
    (a) Write an ionic equation for the reaction that took place. (1 mark)
    (b) Given that the mass of copper deposited was 5 .83g, calculate the molar enthalpy change in kJmof . (specific heat capacity of solution 4.2Jg-1 K-1 ,density of solution = 1.0gcm-3, Cu = 63.5) (2 marks)
  4. Some animal and vegetable oils are used to make margarine and soap.
    Give the reagents and conditions necessary for converting the oils into:
    (a) margarine; (2 marks)
    (b) soap. (1 mark)
    1. (a) Using electrons in the outermost energy level, draw the dot (•) and cross(X)
      Diagrams for the molecules H20 and C2H4.(H =1, C =6,0=8). (2 marks)
      (1) H20
      (ii) C2H4
      (b) The formula of a complex ion is Zn(NH3) 42+
      Name the type of bond that is likely to exist between zinc and ammonia in the complex ion. (1 mark)
  5. Carbon (II) oxide is described as a “silent killer”.
    State one physical property of carbon (II) oxide that makes it a “silent killer.” (1 mark)
    (b) State and explain one chemical property that makes carbon (II) oxide poisonous to human beings. (2 marks)
    16 A sample of fertilizer is suspected to be calcium ammonium nitrate. Describe chemical tests for each of the following ions in the sample:
    (a) calcium ions; (2 marks)
    (b) ammonium ions. (1 mark)
  6. Analysis of a compound showed that it had the following composition:
    69.42% carbon, 4.13% hydrogen and the rest oxygen.
    (a) Determine the empirical formula of the compound.
    (C = 12.0, H = 1.0, 0 = 16.0) (2 marks)
    (b) If the mass of one mole of the compound is 242, determine its molecular formula. (1 mark)
  7. The diagram below represents a set up for large scale manufacture of hydrochloric acid. Study it and answer the questions that follow. (a) Name substance X. (1 mark)
    (b) What is the purpose of the glass beads? (1 mark)
    (c) Give two uses of hydrochloric acid. (1 mark)
    1. The half equations involved in a cell are:
      2H20(t) + 2e — H2(g) + 20H (aq):Eθ = — 0.83V

O2(g) + 2H20(l) + 4e – 40H(aq):Eθ= + O.40V

(a) Write the overall equation for the electrochemical cell -                   (1 mark)

Calculate the e .m .f. generated by a battery consisting ten cells. (1 mark)

State one environmental advantage of using these cells in spacecrafts 
                                                                                                             (1 mark)   
  1. In an experiment to prepare nitrogen (I) oxide, ammonium nitrate was gently heated in a flask.
    (a) Write the equation for the reaction that took place in the flask. (1 mark) (b) State and explain how the gas was collected. (1 mark)
    (c) A sample of the gas was tested with damp blue and red litmus papers. What
    observations were made? (1 mark)
    1. The use of CFCs has been linked to depletion of the ozone layer.
      (a) What does CFC stand for? (1 mark)

(b)Explain the problem associated with the depletion of the ozone layer. (1 mark)

(c) State another environmental problem caused by CFCs.               (1 mark)
  1. Nitrogen and hydrogen react to form ammonia gas as shown in the following
    equation:
    N2(g) + 3H2(g) 2NH3(g): △H is negative

(a) The figure below shows how the percentage of ammonia gas in the equilibrium mixture changes with temperature.

Explain why the percentage of ammonia gas changes as shown in the figure.
(2 marks)

(b) On the axes below, sketch a graph showing how the percentage of ammonia gas in the equilibrium mixture changes with pressure. (1 mark)

  1. The curves below show how the electrical conductivity of hydrochloric and ethanoic acids vary with concentration.

Explain why the electrical conductivity of 0.01M hydrochloric acid is higher than that of O.O1M ethanoic acid. (2 marks)

24 Describe how a solid sample of the double salt, ammonium iron (II) sulphate, can be prepared using the following reagents: Aqueous ammonia, sulphuric (VI) acid and iron metal. (3 marks)

  1. A sample of river water was divided into three portions. The table below shows the tests carried out on the portions and the observations made. (3 marks)

Test Observation Inference

To the first portion, 1cm3 of soap solution was added No lather formed.

The second portion was boiled, cooled and 1cm3 of soap solution was added.
No lather formed
To the third portion, 3cm3 of aqueous sodium carbonate was added, the mixture filtered and 1cm3 of soap solution added to the filtrate.
Lather formed immediately.

Complete the table by filling in the inferences. (3 marks)

26 A water trough, aqueous sodium hydroxide, burning candle, watch class and a graduated gas jar were used in an experimental set up to determine the percentage of active part of air. Draw a labelled diagram of the set up at the end of the experiment. (3 marks)

27 The atomic numbers of phosphorns, sulphur an4l potassium are 15, 16 and 19 respectively. The formulae of their ions are P3 ,, S2- – and K+ . These ions have the same number of electrons.
(a) Write the electron arrangement for the ions. (1 mark)
(b) Arrange the ions in the order of increasing ionic radius starting with the smallest. Give a reason for the order. (2 marks)

CHEMISTRY
PAPER 2- 2010
a). Which of the following compounds; urea, ammonia, sugar and copper (II)chloride
will conduct an electric current when dissolved in water? Give a reason. (2 marks)
b) . The diagram below shows an electrochemical cell. Study it and answer the questions
that follow.
Given the following
Fe2+ (aq) + 2e Fe (s); Eθ = -0.44V
Zn2+ (aq) + 2e Zn (s); E θ = -0.76V
Show on the diagram using an arrow, the direction of flow of electrons. (2 marks)

Name two substances that are used to fill the part labeled L.          (2 marks)

c). In an experiment to electroplate iron with silver, a current of 0.5 amperes was passed through
a solution of silver nitrate for one hour.
Give two reasons why it is necessary to electroplate iron with silver. (2 marks)

Calculate the mass of silver that was deposited on irn (Ag = 108, 1 Faraday = 96,500 coulombs).                                 (2 marks)




a) Give the names of the following compounds:

i).

CH3
CH3 C CH3
CH3 (1 mark)

ii) CH3C Ξ C CH2CH3 (1 mark)

b). Describe a chemical test that can be carried out in order to distinguish between
CH3
CH3 C CH3 and CH3C Ξ C CH2CH3
CH3 (2 marks)
c). Study the flow chart below and answer the questions that follow.

Ethanoic acid
Concentrated Sulphuric (vi)acid 

(2marks)
Name the compounds:
L ………………………………………………………………………………

N ………………………………………………………………………………

Draw the structural formula of compound M showing two repeat units

(1 mark)
Give the reagent and the condition used in step 1. (1 mark)
State the type of reaction that takes place in:
Step 2; (2 marks)

Step 3;

 d).  The molecular formula of compound P is C2H2C14. Draw the two structural formulae of 
compound P.                                 (2 marks)
  1. Use the information in the table below to answer the questions that follow. The letters do not
    represent the actual symbols of the elements.
    Element Atomic number Melting point (0C)
    R
    S
    T
    U
    V
    W 11
    12
    15
    17
    18
    19 97.8
    650.0
    44.0
    -102
    -189
    -64.0 Give reasons why the melting point of:
    S is higher that that of R; (1 mark) V is lower than that of U; (2 marks) How does the reactivity of W with chlorine compare with that of R with chlorine?
    Explain. (2 marks) Write an equation for the reaction between T and excess oxygen. (1 mark) When 1.15g of R were reacted with water, 600cm3 of gas was produced.
    Determine the relative atomic mass of R. (Molar gas volume = 24 000cm3). (3 marks)
    Give one use of element V. (1 mark)
  2. a) 50 cm3 of 1M copper (II) sulphate solution was placed in a 100cm3 plastic beaker.
    The temperature of the solution was measured. Excess metal A powder was added to the
    solution, the mixture stirred, and the maximum temperature of the mixture measured. The
    experiment was repeated using powders of metals B and C. The results obtained are given in
    the below: A B C
    Maximum temperature (OC) 26.3 31.7 22.0
    Initial temperature (OC) 22.0 22.0 22.0 Arrange the metals, A,B,C and copper in order of reactivity starting with the least reactive. Give reasons for the order. (3 marks) Other than temperature change, state one other observation that was made when the most reactive metal was added to the copper (II) sulphate solution. (1 mark)

b). The standard enthalpy change of formation of methanol is -239 kjmol-1.
Write down the thermo chemical equation for the standard enthalpy change of formation of methanol. (1 mark)

Methanol is manufactured by reacting carbon (II) oxide with hydrogen at 3000C and a pressure of 250 atmospheres.

The equation for the reaction is
CO (g) + 2H2(g) CH3OH(g)
How would the yield of methanol be affected if the manufacturing process above is carried out at, 3000C and a pressure of 400 atmospheres? Explain. (2 marks)

Use the following data to calculate the enthalpy change for the manufacture of methanol from carbon (II) oxide and hydrogen.                    (3 marks)

CO(g) + 1/2O2(g) CO2(g); △Hθ = -283kjmol-1
H2(g) + 1/2O2(g) H2O(1); △Hθ = -286kjmol-1
CH3OH(1) + 3/2O2(g) CO2(g) + 2H2O(1); △Hθ=-715kjmol-1

The calculated enthalpy change in part b (ii) (II) above differs from the standard enthalpy change of formation of methanol. Give a reason.     (1 mark)
  1. a) A student set up the apparatus as shown in the diagram below to prepare and collect dry
    ammonia gas. Identify two mistakes in the set up and give a reason for each mistake.
    (3 marks)
    Mistakes …………………………………………………………………………

Reason ……………………………………………………………………………

Mistake …………………………………………………………………………..

Reason …………………………………………………………………………..

Name a suitable drying agent for ammonia                (1 mark)

Write an equation for the reaction that occurred when a mixture of ammonium chloride and calcium hydroxide was heated.              (1 mark)

Describe one chemical test for ammonia gas.             (1 mark)

b) Ammonia gas is used to manufacture nitric (V) acid, as shown below.

This process requires the use of a catalyst. In which unit is the catalyst. In which unit is the catalyst used?                                     (1 mark)
Identify compounds A and B

A ………………………………………………………………………………
B ……………………………………………………………………………….
Using oxidation numbers, explain why the conversation of ammonia to nitric (V) acid is called catalytic oxidation of ammonia. (2 marks)
Ammonia and nitric (V) acid are used in the manufacture of ammonium nitrate fertilizer. Calculate the amount of nitric (V) acid required to manufacture 1000kg of ammonium nitrate using excess ammonia. (3 marks)

(N = 14.0, H = 1.0, O = 16.0)

  1. The melting and boiling points of zinc are 4190C and 907C0 respectively. One of the ores of
    zinc is zinc blende. To extract, the ore is first roasted in air before feeding it into a furnace.
    (i) Write the formula of the main zinc compound in zinc blende. (1 mark)
    (ii) Explain using an equation why it is necessary to roast the ore in air before introducing
    it into the furnace. (2 marks)

(b). The diagram below shows a simplified furnace used in the extraction of zinc.
Study it and answer the questions that follow:

Name two other substances that are also introduced into the furnace together with roasted ore.

(1 mark)
The main reducing agent in the furnace is carbon (II) oxide. Write two equations showing how it is formed. (2 marks)

In which physical state is zinc at point Y in the furnace? Give a reason.

(1 mark)
Suggest a value for the temperature at point X in the furnace.
Give a reason. (1 mark)

State and explain one environmental effect that may arise from the extraction of zinc from zinc blende.                             (2 marks)

Give two industrial uses of zinc.           

(1 mark)

  1. a). The figure below shows how the rate of the following reaction varies with time.
    A(g) + B(g) 2C (g) + D(g) Which one of the two curves represents the rate of the reverse reaction? Give a reason.
    (2 marks)
    What is the significance of points X and Y on the figure? (2 marks) State and explain the effect of an increase in pressure on the rates of the following reactions. H2(g) + CL2(g) 2HCl(g) (2 marks) CH3OH(l) + CH3 COOH(L) CH3COOCH3 (l) + H2O(l)(1 marks) In an experiment to study the rate of reaction between barium carbonate and dilute hydrochloric acid, 1.97g of barium carbonate were reacted with excess 2M hydrochloric acid. The equation for the reaction is

BaCO3(S) + 2HCl(AQ) BaCl2(aq) + CO2(g) + H2O(l).

The data in the table was obtained.

Time in seconds 0 30 60 90 120 150 180 210 240
Volume of gas (cm3) 0 80 135 175 210 230 240 240 240

On the grid provided, plot a graph of volume of gas produced (vertical axis) against time.                          3 marks)





From the graph, determine the rate of the reaction at:


15 seconds;                         (1 mark)

120 seconds;                            (1 mark)


Give a reason for the difference between the two values.    ( 1mark)

233/1
Chemistry
Paper 1
THEORY
Oct./ Nov. 2011
2 hours

(a) What name is given to the process by which alcohol is formed from a carbohydrate?                                   (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(b) Explain why the solubility of ethane in water is lower than that of ethanol.
(2 marks)
Complete the nuclear equation below:
131 131
I Xe +_
53 54
(1 mark)
131
(b) The half-life of I is 8 days. (1 mark)
53
131
Determine the mass of I remaining if 50 grammes decayed for 40 days. (1 mark)
53
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(c) Give one harmful effect of radioisotopes. (1 mark)
…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

A mixture contains ammonium chloride, copper (II) oxide and sodium chloride.

Describe how each of the substances can be obtained from the mixture. (3 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
The set-up below shows how nitrogen gas is prepared in the laboratory.

Describe how nitrogen gas is formed in the flask.           (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Nitrogen is inert. State one use of the gas based on this property. (1 mark)
…………………………………………………………………………………………..
The diagram below represents part of the periodic table. Use it to answer the questions that follow:

Write the electronic arrangement for the stable ion formed by W.    (1 mark)

…………………………………………………………………………………………………………………………………………………………………………………….
Write an equation for the reaction between V and Q (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………
How do the ionization energies of the elements M and T compare? Explain
(1 mark)
……………………………………………………………………………………….……………………………………………………………………………………………..
A certain mass of gas occupies 0.15dm3 at 293K and 98,648.5Pa. Calculate its volume at 101325Pa and 273K. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
When lead (II) nitrate is heated, one of the products is a brown gas.
Write the equation of the reaction that occurs. (1 mark)
…………………………………………………………………………………………………………………………………………………………………………………….
If 0.290dm3 of the brown gas was produced, calculate the mass of the lead(II) nitrate that was heated. (R.F.M of lead (II) nitrate = 331; Molar gas volume = 24dm3)
(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(a) What is meant by a strong acid? (1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………
In an experiment, 40 cm3 of 0.5 M hydrochloric acid was reacted with excess sodium carbonate and the volume of carbon (IV) oxide produced recorded with time. In another experiment, the same volume and concentration of ethanoic acid was also reacted with excess sodium carbonate and the volume of carbon (IV) oxide produced recorded with time.
On the grid below, sketch and label the curves if the volumes of carbon (IV) oxide were plotted against time. (2 marks)

State two reasons why hydrogen is not commonly used as a fuel   (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………
During a class experiment, chlorine gas was bubbled into a solution of potassium iodide.
State the observations made. (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………..
Using an ionic equation, explain why the reaction is redox. (2 marks)
……………………………………………………………………………………………………………………………………………………………………………………
Exhaust fumes of some cars contain carbon (II) oxide and other gases.
………………………………………………………………………………………………………………………………………………………………………………………………
Explain how carbon (II) oxide is formed in the internal combustion engines (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………
Name two gases other than carbon (II) oxide that are contained in exhaust fumes and are pollutants. (2 marks)
……………………………………………………………………………………………………………………………………………………………………………………
Sodium hydroxide can be prepared by the following methods: I and II.
Sodium metal Cold water sodium hydroxide + Hydrogen
Concentrated Process A Sodium hydroxide + Chlorine + Hydrogen Sodium Chloride.

Name one precaution that needs to be taken in method I.     (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………
Give the name of process A. (1 mark)
…………………………………………………………………………………………………………………………………………………………………………………….
(c) Give one use of sodium hydroxide. (1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………
Distinguish between the terns deliquescent a.m.f efflorescent as used in chemistry.
(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Two organic compounds P and Q decolourise acidified potassium manganate (VII) solution; but only P reacts with sodium metal to give a colourless gas. Which homologous series does compound P belongs? Give a reason. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Soap dissolves in water according to the equation below;
Na St(ag) Na(aq) + + St- where St- is the stearate ion.
Write the formular of the scum formed when soap is used in hard water. ( 1mark)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Write the ionic equation for the reaction that occurs when sodium carbonate is used to remove hardness in water. (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………
Ethanoic acid and ethanol react as shown in the equation below:
CH3COOH(l) + C2H5OH(l) __ CH3COOC2H5(l) + H2O(l)

Other than warming, how would the state of equilibrium be established within a short time? (1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………
The set up below was used to prepare a gas and study some of its properties. Study it and answer the questions that follow:

State and explain the observations made in the:
tube labeled A;                     (1 mark)

…………………………………………………………………………………………
beaker labeled B. (1 mark)
State one precaution that should be taken when carrying out this experiment. (1 mark)
…………………………………………………………………………………………
Under certain conditions, chlorine gas reacts with sodium hydroxide to form sodium hypochlorite.
Name the conditions under which sodium hydroxide reacts with chlorine to form sodium hypochlorite. (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………..
State two uses of sodium hypochlorite. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
50 kg of ammonium sulphate (NH4)2 SO4 and 30kg of urea CO (NH2)2 fertilizers were applied in two equal sizes of plots A and B to enrich their nitrogen content. Show by working, which plot was more enriched with nitrogen. (N=14; S= 32; O= 16; H=1)
(3 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Describe how the PH of anti-acid (Actal) powder can be determined in the laboratory.

(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Graphite is one of the allotropes of carbon.
Name one other element which exhibits allotropy         (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………

Explain why graphite is used in the making of pencil leads.     (2 marks)

…………………………………………………………………………………………………………………………………………………………………………………….

The table below gives some properties of three elements in group (VII) of the periodic table. Study it and answer the questions that follows:

Element Atomic No. Melting Point (0C) Boiling Point (0C
Chlorine 17 -101 -34.7
Bromine 35 -7 58.8
Iodine 53 114 184

Which element is in liquid form at room temperature? Give a reason. (1 mark)

…………………………………………………………………………………………………………………………………………………………………………………….

Explain why the boiling point of iodine is much higher than that of chlorine. 

(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

The thermal chemical reaction between carbon and sulphur is as shown by the equation below:

C(s) + 2S2(s) CS2 (l) ∆I = +117.0kJmol-1.

On the grid below, sketch and label the energy level diagram for the reaction.  

(2 marks)

The table below gives the number of electrons, protons and neutrons in substances X, Y and Z. Study it and answer the questions that follow.

Substance Electrons Protons Neutrons
X 10 10 10
Y 10 8 10
Z 8 8 8

Which letter represents an ion?                 (1 mark)

…………………………………………………………………………………………………………………………………………………………………………………….

Which of the substances are isotopes? Give a reason.        (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(a) State the Gay Lussac’s Law.                 (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………

10cm3 of a gaseous hydrocarbon, C2Hx require 30cm3 of oxygen for complete combustion. If steam and 20cm3 of carbon (IV) oxide were produced, what is the value of X?

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

The data given below was recorded when metal M was completely burnt in air. M is not the actual symbol of the metal. (R.A.M ; 56, O = 16)

Mass of empty crucible and lid = 10.240g
Mass of crucible, lid and metal M = 10.35g
Mass of crucible, lid and metal oxide = 10.400g
Determine the mass of: (½ mark)

metal M;

……………………………………………………………………………………………………………………………………………………………………………………..

oxygen.                                  (½ mark)

……………………………………………………………………………………………………………………………………………………………………………………..

Determine the empirical formula of the metal oxide.         (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

The flow chart below shows some processes involved in the industrial extraction  of zinc metal.

















Name one ore from which zinc is extracted.              (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………

Write the equation of the reaction taking place in unit II.     (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………..

Name two uses of Zinc metal.                        (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………

The diagram below shows the bonding between aluminium chloride and ammonia.

H Cl

H N Al Cl

H Cl

Name the types of bonds that exists in the molecule.            (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………

How many electrons are used for bonding in the molecule?        (1 mark)

…………………………………………………………………………………………………………………………………………………………………………………….

Explain why the following substances conduct an electric current.
Magnesium metal.                            (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………

Molten magnesium chloride.                  (1 mark)
A sample of river water is suspected to contain zinc and sulphate ions can be established. (3 marks)                    

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

What name is given to elements which appears in group (11) of the periodic table?

(1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………

233/2
CHEMISTRY
Paper 2
(THEORY)
Oct./Nov.2011
2 hours.

The flow chart below some of the processes involved in large scale product of sulphuric (IV) acid. Use it to answer the questions that follow.



Describe how oxygen is obtained air on a large scale.       (3 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(i) Name substance A.                           (1 mark)

………………………………………………………………………………………………………………………………………………………………………………

  (ii) Write an equation for the process that takes place in the absorption chamber.

(1 mark)
………………………………………………………………………………………………………………………………………………………………………………

Vanadium (V) oxide is a commonly used catalyst in the contact process.


Name another catalyst which can be used for this process.   (1 mark)

………………………………………………………………………………………………………………………………………………………………
Give two reasons why vanadium (V) oxide is the commonly used catalyst.
(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
State and explain the observations made when concentrated sulphuric (VI) acid is added to crystals of copper (II) sulphate in a beaker. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
The reaction of concentrated sulphuric (VI) acid with sodium chloride produces hydrogen chloride gas. State the property of concentrated sulphuric (VI) acid illustrated in this reaction. (1 mark)
………………………………………………………………………………………………………………………………………………………………………………
Name four uses of sulphuric (VI) acid. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
The set-up below was used by a student to investigate the products formed when aqueous copper (II) chloride was electrolysed using carbon electrodes.

(i) Write the equation for the reaction that takes place at the cathode. (1 mark)

………………………………………………………………………………………………………………………………………………………………………………
(ii) Name and describe a chemical test for the product initially formed at the anode when a highly concentrated solution of copper (II) chloride is electrolysed.
(3 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

How would the mass of the anode change if the carbon anode was replaced with copper metal? Explain.             (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
0.6 g of metal B were deposited when a current of 045A was passed through an electrolyte for 72 minutes. Determine the charge on the ion of metal B. (Relative atomic mass of B = 59, 1 Faraday = 96 500 coulombs) (3 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

The electrode potentials for cadmium and zinc are given below:

Cd2+ (ag) + 2e Cd(s); Eө = – 0.4 v
Zn2+ (ag) + 2e Zn(s); Eө = – 0.76v
Explain why it is not advisable to store a solution of cadmium nitrate in a container made of zinc. (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(a)  Ethanol can be manufactured from ethane and steam as shown in the equation below:

C2H4(g) + H2O(g) CH3 CH2 OH(g)
Temperature and pressure will affect the position of equilibrium of the above reaction. Name the other factor that will affect the position of equilibrium of the above reaction. (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………..
(b) The data in the table below was recorded when one mole of ethane was reacted with excess steam. The amount of ethanol in the equilibrium mixture was recorded under different conditions of temperature and pressure. Use the data to answer the questions that follow.
Temperature (0C) Pressure (Atm) Amount of ethanol at
Equilibrium (moles)
300 50 0.40
300 60 0.46
300 70 0.55
250 50 0.42
350 50 0.38

(i)State whether the reaction between ethene and steam is exothermic or
endothermic. Explain your answer. (3 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………\

(ii) State and explain one advantage and one disadvantage of using extremely high pressure in this reaction.
Advantage (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………..
Disadvantage (2 marks)
…………………………………………………………………………………………………………………………………….
In an experiment to determine the rate of reaction between calcium carbonate and dilute hydrochloric acid, 2g of calcium carbonate were reacted with excess 2M hydrochloric acid. The volume of carbon (IV) oxide evolved was recorded at regular intervals of one minute for six minutes. The results are shown in the table below.

Time (minutes) 1 2 3 4 5 6
Volume of
Carbon (IV) oxide (cm3) 170 296 405 465 480 480

Plot a graph of time in minutes on the horizontal axis against volume of carbon (IV) oxide on the vertical axis.            (3 marks)































Determine the rate of reaction at 4 minutes.        (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
(a) When excess calcium metal was added to 50cm3 of 2 M aqueous copper (II) nitrate in a beaker, a brown solid and bubbles of gas were observed.
Write two equations for the reactions which occurred in the beaker. (2 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
Explain why it is not advisable to use sodium metal for this reaction.
(2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(b) Calculate the mass of calcium metal which reacted with copper (II) nitrate solution. (Relative atomic mass of Ca = 40) (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(c) The resulting mixture in (a) above was filtered and aqueous sodium hydroxide added to the filtrate drop wise until in excess. What observations were made? (1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………

(d) (i) Starting with calcium oxide, describe how a solid sample of calcium carbonate can be prepared. (3 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

  (ii)  Name one use of calcium carbonate.                    (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………

(a) Other than their location in the atom, name two other differences between an electron and a proton.                                 (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
The table below gives the number of electrons, protons and neutrons in particles
A, B, C, D, E, F and G.
Particle Protons Electrons Neutrons
A 6 6 6
B 10 10 12
C 12 10 12
D 6 6 8
E 13 10 14
F 17 17 18
G 8 10 8

Which particle is likely to be a halogen?                     (1 mark)

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

What is the mass number of E?                         (1 mark)

…………………………………………………………………………………

Write the formula of the compound formed when E combines with G. 
 (1 mark)
            ………………………………………………………………………………..

Name the type of bond formed in (iii) above.                  (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

How does the radii of C and E compare? Give a reason.       (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Draw a dot (.) and cross (x) diagram for the compound formed between A and F.                                   (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

Why would particle B not react with particle D?         (1 mark)

…………………………………………………………………………………………………………………………………………………………………….

(a) Study the flow chart below and answer the questions that follows
















      I     what observation will be made in step I?    (1 mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………
II Describe a chemical test that can be carried out to show the identity of compound C. (2 marks)
……………………………………………………………………………………………………………………………………………………
Give the names of the following: (2 marks)
I E ……………………………………………………………………
II Substance D…………………………………………………………..
Give the formula of substance B. (1 mark)
……………………………………………………………………………………………………………………………………………………

Name the type of reaction that occurs in:       (1 marks)

I Step (II) …………………………………………………………….
II Step (IV) ……………………………………………………………

Give the reagent and conditions necessary for Step (VI).  (2 marks)

Reagent: ………………………………………………………………
…………………………………………………………………………
Conditions: …………………………………………………………….
…………………………………………………………………………
(b) (i) Name the following structure.

                                                                (1 mark)

………………………………………………………………………………………………………
(ii) Draw the structure of an isomer of pentene. (1 mark)

  1. (a) What is meant by molar heat of combustion? (1 mark)
    ……………………………………………………………………………………………………………………………………………………………………………………………………… (b) State the Hess’s Law. (1 mark)
    ………………………………………………………………………………………………………………………………………………………………………………………………………
    Use the following standard enthalpies of combustion of graphite, hydrogen and enthalpy of formation of propane
    ∆HөC (Graphite) = -393kJMol-
    ∆HөC (H2 (g)) = -286kJ mol-1
    ∆Hөf (C3 H8 (g)) = – 104kJ mol-1 Write the equation for the formation of propane. (1 mark)
    …………………………………………………………………………………
    Draw an energy cycle diagram that links the heat of formation of propane with its heat of combustion and the heats of combustion of graphite and hydrogen.(3 marks) Calculate the standard heat of combustion of propane. (2 marks)
    ……………………………………………………………………………………………………………………………………………………………………..
    (d) Other than the enthalpy of combustion, state one factor which should be considered when choosing a fuel. (1 mark)
    ……………………………………………………………………………………………………………………………………………………………………………………………… The molar enthalpies of neutralization for dilute hydrochloric acid and dilute nitric (V) acid are -57.2 kJ/ mol while that of ethanoic acid is -55.2 kJ/mol. Explain this observation. (2 marks)
    ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

233/3
CHEMISTRY
Paper 3
PRACTICAL
Oct./Nov. 2011
2 ¼ hours

You are provided with:

1.60g of solid A, a dibasic acid.
Solution B containing 4.75g per litre of salt B.
Aqueous sodium hydroxide, solution C
Phenolphalein indicator.

You are required to prepare a solution of solid A and use it to determine the:-

Concentration of sodium hydroxide, solution C
React salt B with excess sodium hydroxide and then determine the relative molecular mass of salt B.

Procedure I
Using a burette, place 25.0cm3 of solution B in each of two 250ml conical flasks.Using a pipette and pipette filler, add 25.0cm3 of solution C to each of the two conical flasks. (The sodium hydroxide added is in excess). Label the conical flasks 1 and 2.

Heat the contents of the first conical flask to boiling and then let the mixture boil for 5 minutes. Allow the mixture to cool.
Repeat procedure (b) with the second conical flask.

While the mixture are cooling, proceed with procedure II.

    Procedure II 
Place all solid A in a 250ml volumetric flask. Add about 150cm3 of distilled water, shake well to dissolve the solid and then add water to make up to the mark. Label this as solution A.

Place solution A in a clean burette. Using a pipette and pipette filler, place 25.0cm3 solution C in a 250ml conical flask. Add 2 drops of phenolphthalein indicator and titrate with solution A. Record your results in table 1. Repeat the titration two more times and complete the table.

I II III
Final burette reading
Initial burette reading
Volume of solution A used (cm3)

                                    (4 marks)

Calculate the:-
Average volume of solution A used: (½ marks)
…………………………………………………………………………………

Concentration in moles per litre of the dibasic in solution A;  (2 marks)

(Relative molecular mass of A is 126).
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

Moles of the dibasic acid used;                 (1 mark)

…………………………………………………………………………………………………………………………………………………………………………..

Moles of sodium hydroxide in 25.0 cm3 of solution C.        (1 mark)

…………………………………………………………………………………………………………………………………………………………………….

Concentration of sodium hydroxide in moles per litre.       (2 marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

    Procedure III

Add 2 drops of phenolphthalein indicator to the contents of the first conical flask prepared in procedure I and titrate with solution A. Record your results in Table 2. Repeat the procedure with the contents of the second conical flask and complete the table.

Table 2

1st conical flask 2nd conical flask
Final burette reading
Initial burette reading
Volume of solution A used (cm3)

                                        (3 marks)
    Calculate the:-
Average volume of solution A used;                  (½ mark)

…………………………………………………………………………………………
Moles of the dibasic acid used; (1 mark)
……………………………………………………………………………………………………………………………………………………………………………………………………………………..
Moles of sodium hydroxide that reacted with the dibasic acid. (1 mark)
…………………………………………………………………………………………………………………………………………………………………………………….
Moles of sodium hydroxide that reacted with 25.0cm3 of salt B in solution B;
(2 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………
Given that mole of salt B reacts with 2 moles of sodium hydroxide, calculate the:
Number of moles of salt B in 25.0cm3 of solution B; (1 mark)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
Concentration in mole per litre of salt B in solution B; (1 mark)
……………………………………………………………………………………………………………………………………………………………………
relative molecular mass of salt B; (2 marks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(a) You are provided with solid D. Carry out the following tests and write your observations and inferences in the spaces provided.
Place about one half of solid D in a test-tube and heat it strongly. Test any gases produced with both red and blue litmus papers.

Observations Inferences

( 2 marks) (1 mark)

Place the rest of solid D in a boiling tube. Add about 10cm3 of distilled water. Shake well.

To a 2cm3 portion of the solution, add about 1cm3 of hydrogen peroxide and shake well. To the resulting mixture, add aqueous sodium hydroxide drop wise until in excess.

Observations Inferences

( 1 marks) (1 mark)

(b) You are provided with solution E. Carry out the following tests and write your observations and inferences in the spaces provided.
Divide solution E into two portions.

To one portion of solution E in a test-tube, add 3 drops of barium nitrate. Retain the mixture for use in test (ii) below.

Observations Inferences

( 1 mark) (2 marks)

To the mixture obtained in (i) above, add about 5cm3 of 2M nitrate (V) acid.

Observations Inferences

( 1 mark) (1 mark)
To portion two of solution E in a test-tube, add 2 drops of acidified potassium dichromate (IV) and warm the mixture.

Observations Inferences

( 1 mark) (1 mark)

You are provided with liquid F. Carry out the following tests and record your observations and inferences in the spaces provided.
Place five drops of liquid F on a clean dry watch glass and ignite it.

Observations Inferences

( 1 mark) (1 mark)

Place about 2 cm3 of liquid F in a clean dry test-tube, add all the sodium hydrogen carbonate provided.

Observations Inferences

( 1 mark) (1 mark)

Place about 2cm3 of liquid F in a test- tube, add about 1cm3 of acidified potassium dichromate (IV) and warm the mixture.

Observations Inferences

( 1 mark) (1 mark)