Name: …………………………………………… Index No …………………
Candidate’s sign…………………..
Date: ……………………………….
233/2
CHEMISTRY
Paper 2 (Theory)
July/ August 2013
Time: 2 Hours
Kenya Certificate of Secondary Education (K.C.S.E.)
CHEMISTRY
Paper 2
July/ August 2013
Time: 2 Hours
INSTRUCTIONS TO CANDIDATES:
Write your name and index number in the spaces provided above.
Sign and write the date of examination in the spaces provided above.
Answer all the questions in the spaces provided.
All workings must be clearly shown where necessary.
For Examiner’s Use only.
QUESTION MAXIMUM SCORE CANDIDATE’S SCORE
1 12
2 12
3 13
4 13
5 12
6 08
7 10
Total score 80
This paper consists of 11 printed pages. Candidates should check to ascertain that all pages are printed as indicated and that no
questions are missing.
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©Ndhiwa District Form Four-2013 Chemistry 2
1. Use the standard electrode potential for elements A , B, C, D and F given below to
answer the questions that follow. The letters do not represent the actual symbols of the
elements.
Eθ
A2+ (aq) + 2e- A (s) -2.90
B2+ (aq) + 2 e- B (s) -2 .38
C+ (aq) + 2 e- ½ C2 (g) 0.00
D2+ (aq) + 2 e- D (s) + 0.34
F(g) + e- F- (aq) + 2.87
(a) (i) What is the Eθ values of the strongest reducing and oxidizing agents (1mk)
…………………………………………………………………………………………
…………………………………………………………………………………………
(ii) What is the Eθ value of the electrochemical cell constructed between half cells of
element A and F (2mks)
…………………………………………………………………………………………
…………………………………………………………………………………………
(iii) In the spaces provided draw a labelled diagram of electrochemical cell that would
be obtained when half cells of element A and F are combined. (2mks)
(iv) On the diagram drawn above show the direction of the flow of electric current
( ½ mk)
(b) (i) What is Binary electrolyte? (1mk)
…………………………………………………………………………………………
…………………………………………………………………………………………
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©Ndhiwa District Form Four-2013 Chemistry 2
(ii) The diagram below represents a set up that can be used for electrolysis of an
aqueous copper (ii) chloride. Study it and answer the questions that follows.
cell
Switch
k
Pt electrodes
Pt electrode electrodes
CuCl2 (aq)
(iii) On the diagram:
(I) Indicate the anode and the cathode electrodes ( ½ mk)
(II) Write ionic equations for the reactions of the
Anode ( ½ mk)
………………………………………………………………………………………
………………………………………………………………………………………
Cathode ( ½ mk)
………………………………………………………………………………………
………………………………………………………………………………………
(iv) State the observation made at the cathode (1mk)
………………………………………………………………………………………
………………………………………………………………………………………
(c) In a experiment the quantity of electricity passed to deposit 3.57g of metal Q from its
salt solution was 11500 coloumbs (RAM of Q = 119, Faraday = 96500C)
(i) Calculate the number of Faradays required to deposit one mole of Q(3mks)
(ii) The cation in the salt has the formula QY+. What is the numerical value of
Y (1mk)
2. (a) (i) What is thermochemical equation (1mk)
………………………………………………………………………………………
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©Ndhiwa District Form Four-2013 Chemistry 2
(ii) In an experiment to determine the heat of combustion of compound X, a scholar at
Cyprass College used heat from the burning compound of X to heat 100cm3 of
water in a beaker. He obtained the following results.
(a) Volume of water in the beaker = 100cm3
(b) Initial temperature of water = 17oC
(c) Final temperature of water = 420C
(d) Initial mass of burner + compound N = 10.5g
(e) Final mass of burner + compound N = 10.2g.
(I) Determine the mass of compound burnt ? (1mk)
(II) Calculate the rise in temperature ? (1mk)
(III) Determine the amount of heat produced by the compound
(specific heat capacity 4200J g-1 k-1, density of H2O = 1g/cm3) (2mks)
(IV) Calculate the molar heat of combustions of compound X
(R.mm of X = 256) (2mks)
(iii) Use the following thermochemical equations below to answer the questions that
follow.
(a) C2H6 (g) + 7/2 O2 (g) 2CO2(g) + 3H2O (s) ∆H1, = -1560kJmol-1
(b) C (graphite) + O2(g) CO2 (g) ∆H2 = - 394 kJ mol-1
(c) H2 (g) + ½ O2(g) H2O(l) ∆H3 = - 286 kJ mol-1
(I) Calculate the molar enthalpy of combustion of C2H6. (2mks)
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©Ndhiwa District Form Four-2013 Chemistry 2
(II) Draw an energy level diagram for the reaction represented by equation (i) above
(3mks)
(i) What is fuel?
(1mk)
…………………………………………………………………………………………………
………………………………………………………………………………………………….
3(a) (i) What are unsaturated hydrocarbon compounds ? (1mk)
…………………………………………………………………………………………………
(ii)Give the names of the following organic compounds.
CH3
(I) CH3 - C - CH3
CH3
(II) CH2 CH CH2 CH CH2
(b) The scheme below shows a series of reaction starting with propanol
Solution A +
K(s)
CH3 CH2 NaOH
COOH F
H+ / KMO4 (aq)
Step I Butan – l –ol Step (iii)
CH3 CH2 CH2 OH Conc. H2SO4
Step (iv) heat CH3 CH3
0
Conc. H2SO4 180 C
1 mole of Cl2(g)
Product C +
B H2O (l) Compound + HCl
HCl
CH2 CH E
Step (ii)
CH3 G
CH2 - C
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©Ndhiwa District Form Four-2013 Chemistry 2
H n
(i) Name the type of reaction in steps (I) and (II) (1mk)
………………………………………………………………………………………
(ii) Write equation for the reaction that takes place in step III
(1mk)
……………………………………………………………………………………
(iii) Name substances A, B , C , D , E and F (3mks)
A……………………….
B…………………………
C…………………………
D………………………..
E…………………………
F…………………………
(iv) Draw the structural fomular of compound C
(1mks)
(c) (i) Name the process in step IV (1mk)
………………………………………………………………………………………...
(ii)State the type of reactions involved in formation of compound B. (2mks)
……………………………………………………………………………………….
……………………………………………………………………………………….
(iii)If the relative molecular mass of G is 35,700 determine the value of n (2mks)
(iv)Below are structures of two cleaning agents.
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©Ndhiwa District Form Four-2013 Chemistry 2
R – COO- Na+ X
R OSO3 – Na+ Y
(I) Identify the cleaning agent suitable for use in water containing mg Cl2 ( ½ mk)
…………………………………………………………………………………….
(II) State one disadvantages of using this cleaning agent ( ½ mk)
……………………………………………………………………………………..
……………………………………………………………………………………..
3. Study the following part of periodic table chart and use it to answer the questions that
follows. The letters are of the actual symbols of the elements.
S C D E
F G
H
B
(a) (i) Which elements form ions with charge of -2. Explain (1mk)
……………………………………………………………………………………………
……………………………………………………………………………………………
(ii)Compare the ionic radius of C and E. Explain (2mks)
…………………………………………………………………………………………..
………………………………………………………………………………………….
(iii)Write the formular of the compound formed between element G and H (1mk)
……………………………………………………………………………………………
……………………………………………………………………………………………
(iv)In terms of structure of bonding, explain why the oxides of D has a lower melting
point than that of G (2mks)
……………………………………………………………………………………………
……………………………………………………………………………………………
(v)Write an equation to show the action of heat on nitrates of F and G (1mk)
……………………………………………………………………………………………
……………………………………………………………………………………………
(b) (i) What is electron affinity? (1mk)
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©Ndhiwa District Form Four-2013 Chemistry 2
……………………………………………………………………………………………
(ii)Elements E and H are in the same group in the periodic table. Which of these two
elements is most reactive . Explain. (1mk)
……………………………………………………………………………………………
5. (a) Nitrogen is an unreactive gas .Explain (1mk)
……………………………………………………………………………………………..
…………………………………………………………………………………………….
(b) The set up below is used to prepare nitric acid
Glass
cork
Red brown
fumes
Mixture
X
(i) Name the reagents in mixture X (1mk)
………………………………………………………………………………………
………………………………………………………………………………………
(ii) Write an equation for the reaction which takes place in the glass retort (1mk)
………………………………………………………………………………………
(c) Ammonia can be formed by the reaction shown below
N2 (g) + 3H2 (g) 2NH3 (g) ; ∆H = - 92kJ/mol
State and explain what happens if :
(i) The volume of the system is increased (1mk)
…………………………………………………………………………………………
…………………………………………………………………………………………….
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©Ndhiwa District Form Four-2013 Chemistry 2
(ii) Cold water is poured over the system (1mk)
……………………………………………………………………………………………
……………………………………………………………………………………………
(d) The diagram below represents a sketch of a set – up for the study of a property of
hydrogen.
H2 gas
Solid Q
(i) Complete the diagram by showing how hydrogen gas can be passed over heated
copper(ii) oxide safely (2mks)
(ii) Name the solid Q and state its functions (1mk)
………………………………………………………………………………………………
………………………………………………………………………………………………
(iii) State and explain the observations that would be made when hydrogen gas was
passed over hot copper (ii) oxide. (3mks)
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
(iv) Write an equation for the reaction observed in (iii) above. (1mk)
………………………………………………………………………………………………
…………………………………………………………………………………………
6. (a) Sulphur is mined using the Frasch process which uses super heated water at 1700C and
hot compressed air.
(i) Explain how water at 1700C is obtained (1mk)
……………………………………………………………………………………………..
(ii) What is the role of superheated water? (1mk)
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©Ndhiwa District Form Four-2013 Chemistry 2
………………………………………………………………………………………………
(iii) State the role of compressed air (1mk)
………………………………………………………………………………………………
(b) In a experiment, 3.6g sulphur were obtained by reacting hydrogen sulphide as sulphuric
(iv) oxide as shown in the equation below:
2H2S(g) + SO2 (g) 2H2O(l) + 3S(s)
Given that the yield of sulphur is 75%. Calculate the volume of SO2 used at room
temperature and pressure. (H=1, S=32, O=16, molar gas volume at r.t.p is 24dm3)(3mks)
(c) Study the flowchart below and answer the questions that follow.
Air SO2 (g) Purifier Clean Water
Solid A
Air SO2 Solution L Air
Excess NaOH
Solution M
Barium White
nitrate precipitate
(i) Other than sulphur, name two possible identities of solid A
(1mk)
………………………………………………………………………………………………
………………………………………………………………………………………………
(ii) Write an ionic equation for the formation of the white precipitate
(1mk)
………………………………………………………………………………………………
(iii) State and explain the observations made when red and blue litmus papers were dipped
into solution L (1mk)
………………………………………………………………………………………………
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©Ndhiwa District Form Four-2013 Chemistry 2
………………………………………………………………………………………………
(iv) State and explain the observation made when dilute hydrochloric is mixed with the
white precipitate
(1mk)
………………………………………………………………………………………………
………………………………………………………………………………………………
7. Study the information below and answer the questions that follow:
Formula of the chloride NaCl MgCl2 AlCl2 SiCl4 PCl3 SCl2
M.P(0C) 801 714 - -70 -91 -80
Formula of the oxide Na2O MgO Al2O3 SiO2 P4O10 SO2 Cl2O7
M.P(0C) 1190 3080 2050 1730 560 -73 -90
(a) Aluminium chloride AlCl3, has an unexpected bond type and structure.
(i) State the type of bond and the structure in AlCl3
Bond type …………………………………………………………… ( ½ mk)
Structure ………………………………………………………………. ( ½ mk)
(ii) What type of bonding would AlCl2 be expected to have why? (1mk)
………………………………………………………………………………………………
………………………………………………………………………………………………
(iii) Why is the melting point of AlCl3 not indicated in the table above? (1mk)
………………………………………………………………………………………………
(b) A piece of blue litmus paper is placed in a solution of sodium chloride and a solution
of aluminium chloride. Explain what would be observed in each case.
Sodium chloride solution (1mk)
…………………………………………………………………………………………..
Aluminium chloride solution (2mks)
…………………………………………………………………………………………
…………………………………………………………………………………………
(c) Explain the large difference in the melting point of the compound of formula MgO
and P4O10 (2mks)
11
©Ndhiwa District Form Four-2013 Chemistry 2
…………………………………………………………………………………………
…………………………………………………………………………………………
(d) Write down the equations for the reaction between the compounds of formula Na2O
and water. (1mk)
…………………………………………………………………………………………
(e) Silicon (iv) chloride gets hydrolyzed by water . Write a balanced equation for this
reaction (1mk)
………………………………………………………………………………………
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©Ndhiwa District Form Four-2013 Chemistry 2
