Name: ……………………………………..

……… Admission Number: …………………

School: ……………………………………… Class: ………………………………………..
Signature: ………………………………….. Date: …………………………………………
Instructions to Candidates
(a) Write your name and admission number in the spaces provided.
(b) Write the name of the school and Sign in the spaces provided.
(c) Answer all the questions in the spaces provided in the question paper.
(d) Non-programmable silent electronic calculators and KNEC mathematical tables
may be used.
(e) All working must be clearly shown where necessary.
(f) This paper consists of 16 printed pages.
(g) Candidates should check the question paper to ascertain that all pages are
printed as indicated and that no questions are missing.
(h) Candidates should answer the questions in English.

FOR EXAMINER’S USE ONLY:

Questions Maximum Score Candidates’ Score
1 12
2 13
3 12
4 12
5 11
6 10
7 10
TOTAL 80
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1. (a) Study the information given below and answer the questions that follow.
Element Atomic Ionic Formula Melting point of
radius radius of oxide oxide (ºC)
(nm) (nm)
P 0.364 0.421 A2 O -119
Q 0.830 0.711 BO2 837
R 0.592 0.485 E2 O 3 1466
S 0.381 0.446 G2 O5 242
T 0.762 0.676 JO 1054
(i) Which elements are non-metals? Give a reason. (2marks)
………………………………………………………………………………………
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(ii) Explain why the melting point of the oxide of R is higher than that of
the oxide of S. (2marks)
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(iii) Give two elements that would react vigorously with each other.
Explain your answer. (2marks)
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 3

(b) Study the information in the table below and answer the questions that
follow (The letters do not represent the actual symbols of the elements)
Ionization Energy_KJ/Mole
Element Electronic configuration 1st 1.E 2nd 1.E
A 2.2 900 1800
B 2.8.2 736 1450
C 2.8.8.2 590 1150
(i) What chemical family do the elements A, B and C belong? (1mark)
………………………………………………………………………………………
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(ii) What is meant by the term ionization energy? (1mark)
………………………………………………………………………………………
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(iii) The 2nd ionization energy is higher than the 1 st ionization energy of
each. Explain. (1mark)
………………………………………………………………………………………
………………………………………………………………………………………
……………………………………………………………………………………….
(iv) When a piece of element C is placed in cold water, it sinks to the
bottom and an effervescence of a colourless gas that bums
explosively is produced. Use a simple diagram to illustrate how this
gas can be collected during this experiment. (3marks)
 4

2. Use the flow chart below to answer the questions that follow.

Br2 (g)

Na2CO3

(i) Name the following;

(i) Gas L (1mark)
………………………………………………………………………………………
……………………………………………………………………………………….
(ii) Gas H (1mark)
………………………………………………………………………………………
……………………………………………………………………………………..
(iii) K (1mark)
………………………………………………………………………………………
………………………………………………………………………………………
(ii) Name the processes involved in the following steps:
(i) Step I (1mark)
………………………………………………………………………………………
……………………………………………………………………………………….
 5

(ii) Step II (1mark)

………………………………………………………………………………………
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(iii) Step III (1mark)
………………………………………………………………………………………
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(iii)Draw the structure of compound E. (1mark)
………………………………………………………………………………………………
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(iv) Write a chemical equation for the complete combustion of substance F.
(1mark)
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……………………………………………………………………………………………….
(v) Name the condition and reagents in step III:
(i) Condition. (1mark)
………………………………………………………………………………………
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(ii) Reagent (1mark)
………………………………………………………………………………………
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(vi) Calculate the mass of salt Q that would be formed by using 21.9kg of G
when it reacts with excess sodium hydroxide. (2marks)
(C = 120, H = 1.0, Na = 23.0, O = 16.0)
 6

(iv) Draw the structure of polymer D. (1mark)

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3. The following set – up was made in an experiment by a group of form four
students. The readings of the balance before and after experiment were indicated
in the diagram below. Given that the initial and the final temperature of water
was 26.70C and 28.00C respectively. The specific heat capacity of water is
4200Jkg-1k-1

Thermometer

50cm3 of water of
density 1g/cm-3

Tripod stand

Determine:
(a) Temperature change that occurred. (1mark)
…………………………………………………………………………………………………
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………………………………………………………………………………………………..
(b) Amount of ethanol used. (1mark)
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(c) Moles of ethanol used. (2marks)
 7

…………………………………………………………………………………………………
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(d) Amount of heat gained by water. (2marks)
…………………………………………………………………………………………………
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(e) Molar enthalpy of combustion of ethanol. (2marks)
…………………………………………………………………………………………………
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(f) Use the following thermochemical processes to answer the questions that
follow;
C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) Hc = -125kJmol-1
C(s) + O2(g) CO2(g) Hc = - 393kJmol-1
H2(g) + ½ O2(g) H2O(l) Hc = -286kJmol-1
(i) Draw an energy level diagram representing the formation and
combustion processes of propane, carbon and hydrogen. (2marks)
……………………………………………………………………………………………
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……………………………………………………………………………………………
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(ii) Hence or otherwise, determine the heat of formation of propane.
(2marks)
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 8

4. (a) The diagram below represents the extraction of sulphur by the frasch
process.

B
C

Level
Ground

(i) Identify and state the use of the substances that pass through tubes A
and C. (2marks)
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
(ii) Rhombic and monoclinic are Allotropes of sulphur. They are inter
convertible as shown below.
96oC

Rhombic ⇌ Monoclinic
I. What does the temperature 96oC represent. (1mark)
………………………………………………………………………………………
………………………………………………………………………………………
II. State the differences in crystalline appearances between rhombic
and monoclinic crystals. (1mark)
………………………………………………………………………………………
………………………………………………………………………………………
 9

(b) The following scheme represents the steps followed in the contact
process, study it and answer the questions which follow.

(i) Name three possible identities of solid A. (1mark)

……………………………………………………………………………………
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(ii) Name two impurities removed by the purifier. (1mark)
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(iii) Why is it necessary to remove impurities. (1mark)
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 10

(c) The following chemical equation shows a reaction taking place in the
catalytic chamber/converter.
2SO2S+ O2(g) ⇌ 2SO3 (g) D Ho= -197kjmol-1
(i) How would the following factors affect the production of sulphur
(IV) oxide.
I. Increase in temperature. (1mark)
………………………………………………………………………………
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II. Decrease in pressure (1mark)
………………………………………………………………………………
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(ii) Name the catalyst which is commonly used in this process and
why? (1mark)
…………………………………………………………………………………
…………………………………………………………………………………
(iii) State and explain one environmental effect of sulphur (IV) oxide
in the atmosphere. (2marks)
…………………………………………………………………………………
…………………………………………………………………………………
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 11

5. (a) The diagram below shows the set up that can be used to obtain nitrogen gas
in an experiment carried out by form 3 of Otieno Oyoo Boys High Schol.

Tube K Copper (ii) oxide

Dry ammonia Nitrogen gas
gas
Heat Beaker
Water

Liquid L Ice

(i) How is the ammonia gas from this process dried? (1mark)
………………………………………………………………………………………………
………………………………………………………………………………………………
(ii) Name liquid L? (1mark)
………………………………………………………………………………………………
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(iii) What observation would be made at tube K at the end of the experiment?
(1mark)
………………………………………………………………………………………………
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(iv) Write an equation for the reaction that took place in the tube K. (1mark)
………………………………………………………………………………………………
……………………………………………………………………………………………….
(v) At the end of the experiment the pH of water in the beaker was found to be
10.0. Explain. (1mark)
………………………………………………………………………………………………
……………………………………………………………………………………………….
 12

(b) A student set up the following apparatus for preparing jars of dry ammonia
but found that no gas collected in the gas jars, although a reaction occurred
in the flask.

Heat Ammonium Dry agent

chloride

(i) Explain why there was no gas collected? (1mark)

………………………………………………………………………………
………………………………………………………………………………
(ii) The following alteration were made
 Using a mixture of ammonium chloride and an alkali,
Ca(OH)2 instead of NH4CL
 The flask was made to slope with neck downward.
State the reason for each alteration above. (2marks)
………………………………………………………………………………………
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(iii) When ammonia gas is passed into a jar of hydrogen chloride
gas, white fumes are formed. Explain with an aid of equation
of reaction. (2marks)
………………………………………………………………………………
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 13

(iv) Ammonia decompose if sparked electrically, what would you

expect to be the products of the decomposition? (1mark)
………………………………………………………………………………
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6. The table below shows the change in concentration of Bromine liquid against
time.
Concentration of Br2 (l) Time in minutes
mol/dm3
10.0x103 0
8.1 x 103 1
6.6 x 103 2
4.4 x103 4
3.0 x103 6
2.0 x103 8
1.3 x103 10
(a) Plot a graph of concentration of bromine (vertical axis) against time.
(3marks)
 14

(b) From the graph determine

(i) The concentration of bromine at the end of 3 minutes. (1mark)
………………………………………………………………………………………
………………………………………………………………………………………
(ii) The rate of reaction at t = 1 ½ minutes. (2mark)
………………………………………………………………………………………
………………………………………………………………………………………
……………………………………………………………………………………..

(b) Explain how the concentration of bromine affects the of the reaction.
(2marks)
…………………………………………………………………………………………………
…………………………………………………………………………………………………
………………………………………………………………………………………………….
 15

(c) On the same axis, sketch the curve that would be obtained if the reaction was
carried out at 200C and label the curve as curve II. Give a reason for your
answer. (2marks)
……………………………………………………………………………………………………
……………………………………………………………………………………………………
…………………………………………………………………………………………………

7. A student was supplied with a colourless liquid supposed to be water.

(a) (i) Describe one chemical test that could have been used to that the
liquid was water. (2marks)
……………………………………………………………………………………………
……………………………………………………………………………………………
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…………………………………………………………………………………………
(iii)How could it have been shown that it was pure water? (1mark)
……………………………………………………………………………………………
……………………………………………………………………………………………
…………………………………………………………………………………………..
(b) The flow chart below shows the various stages of water treatment.

Water reservation Filtration unit I Process Y

Filtration
unit II

Addition of
Tap water
Sodium hypochlorite
 16

(i) Which substance are likely to be removed in filtration unit 1?

(1mark)
………………………………………………………………………………………
………………………………………………………………………………………
(ii) What is the name of Process Y? (1mark)
………………………………………………………………………………
………………………………………………………………………………
(iii) What is the purpose:
I. Process Y? (1mark)
………………………………………………………………………
………………………………………………………………………
II. Addition of solution hypochlorite? (1mark)
………………………………………………………………………
……………………………………………………………………….
(c) It was confirmed that magnesium sulphate was in the tap water.
(i) What type of hardness was present in the water. (1mark)
…………………………………………………………………………………………
…………………………………………………………………………………………
(ii) Explain how the hardness can be removed. (2marks)
…………………………………………………………………………………………
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