Name: ………………………………………………………………….Adm. No…………………..

Index No………………………………………………………………

END OF TERM ONE 2018 EXAMS

233/1
CHEMISTRY
PAPER 2
THEORY

1. The grid below represents part of the periodic table. Study it and answer the questions that follow. The
letters do not represent the actual symbols of the elements.

A K
B D G I
C F H
E J

a) i) Which letter represents an element that is least reactive. (1mk)

ii) Why are elements D and E referred to as alkaline earth metals. (1mk)

b) How does the atomic radius of F and H compare? (2mks)

c) Select two letters representing a pair of elements that would react most explosively.(1mk)

d) Write an equation showing how element D forms its ions. (1mk)

Page 1 of 11 Form 4 Chemistry Exams Term 1 2018

e) Write the formulae of :
i) Bromide of D (1/2 mk)

ii) Sulphate of C (1/2 mk)

f) What type of bonding exist between:

i) E and J (1/2 mk)

ii) G and J (1/2mk)

g) Explain why the melting point of J is higher than that of I (2mks)

h) An element Z has atomic number 14.

I) Indicate on the grid the position of the element. (1mk)

II) Write the formula of the oxide of element Z (1mk)

i) When 1.15g of C were reacted with water, 600cm3 of gas was produced. Determine the reactive atomic
mass of C. (Molar gas volume = 24 000cm3) (3mks)

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2. The flow chart below outlines the manufacture of several important fertilizer. Use it to answer the questions
that follow:
Sulphur (IV) Oxide

contact + Water Sulphuric (vi)

F
Process acid

E
oxygen

Nitrogen

Haber B
A
Hydrogen Process

T Oxidation C

Lime or
Nitric (v) acid
D
Limestone

a) i) Identify substance A,B,C,D,E and F (3mks)

A -
B -
C -
D -
E -
F -
ii) From which industrial process can sulphur be obtained? (1mk)

iii) State the condition necessary for conversion of sulphur (IV) oxide to sulphur (VI) oxide in the
contact process. (2mks)

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 iv) State one source of hydrogen used in the haber process. (1mk)

v) Calculate the composition of nitrogen in B

b) i) Name substances X and Y (2mks)

ii) Give one source of substance X used in the process above (1mk)

iii)What is the purpose of substance Y in the process above? (1mk)

iv)Write an equation from the reaction producing hydrogen chloride gas in the above process.(1mk)

3. i) Give the names of the following compounds.

I) CH3 CH2 CH2 CH2 OH (1mk)

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II) CH3 COOCH2CH3 (1mk)

ii) One of the two formulae in (a) above represents a sweet smelling compound. Give the names of the
two organic compounds that can be used to prepare this compound in the laboratory. (2mks)

iii)Ethane and Ethene react with Bromine according to the following equations given below:
I) C2H6(s) + Br2(g) C2H5Br(l) +HBr(g)

II) C2H4(g) + Br2(g) C2H4Br2(l)

Name the type of bromination reaction taking place in:

(i) (1mk)

(ii) (1mk)

iv) A certain polymer has the following structure

CH −CH 2−CH −CH 2

C6H5 C 6H 5

What is meant by polymerization? (1mk)

b)Study the scheme given below and answer the questions that follow.

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 I) Name the reagents used in:
Step 1 (1mk)

Step 2 (1mk)

II) Identify substances:

Q (1mk)

R (1mk)

P (1mk)

4. In an experiment to determine the heat of combustion of methanol, CH 3OH, a student used a set up like the one
shown in the diagram below. Study the set up and the data below it and answer the questions that follow

Volume of water = 500cm3

Final temperature of water= 27.0oC
Initial temperature of water = 20.0oC
Final mass of lamp + methanol = 22.11grams
Initial mass of lamp + Methanol = 22.98grams
Density of water = 1.0g/cm3
Specific heat capacity = 4.25Jg-1oC-1

I) Calculate:
a) The number of moles of methanol used in the experiment. (C=12, O=16, H=1) (2mks)

Page 6 of 11 Form 4 Chemistry Exams Term 1 2018

 b) The heat change in the experiment (1mk)

c) The heat of combustion per mole of methanol (2mks)

II) Explain why the value of the molar heat of combustion of methanol obtained in this experiment is different
from the theoretical value. (1mk)

III) On the axis below draw an energy level diagram for the combustion of the methanol (2mks)

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IV) Use the information below to answer the questions that follow:
Ca(s) + ½ O2(g) CaO(s) H= -635KJ/mole
C(s) + O2(g) CO2(g) H = -394KJ/mole
3
Ca(s) + C(s) + O2(g) CaCO3 H = -1207KJ/mole
2

Use energy cycle diagram to calculate the enthalpy change for the reaction:
Ca(s) + CO2(g) CaCO3(s) (3mks)

5. The table below gives some properties of gas Q and P.

Gas Density Effect on water

Q Higher than air Dissolves readily
P Heavier than air No effect

a) Describe how you would obtain a pure sample of gas P from a mixture of gas Q and P (2mks)

b) Carbon tetrachloride (CCl4) was added to a solution of iodine and sodium chloride. The mixture was
then placed in a separating funnel and two layers formed as shown below.

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 I) What is the name given to a mixture with layers like in the above? (1mk)

II) Identify the piece of apparatus used in the separation. (1mk)

c) i) What was the purpose of adding carbon tetrachloride? (1mk)

ii)Name the major components of the layer labeled A (1mk)

d) Describe briefly how common salt is separated from trona at Lake Magadi. (2mks)

6. In an experiment to determine the percentage of impurity in sodium carbonate, 1.8g of impure sodium carbonate
was reacted with excess 2M hydrochloric acid. 340cm 3 of dry carbon (iv) oxide gas was collected during the
experiment at room temperature and pressure.
(Na=23. O=16, C=12) molar gas volume at r.t.p. = 24dm3)
a) Why was excess 2M hydrochloric acid used in the experiment? (1mk)

b) Write an equation for the reaction that produced carbon (iv) oxide. (1mk)

c) Calculate:
I) The number of moles of carbon (iv) oxide produced. (2mks)

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 II) The number of moles of sodium carbonate that reacted with the acid. (2mks)

III) The mass of sodium carbonate that reacted with the acid. (2mks)

IV) The percentage of impurities in the sample of sodium carbonate. (2mks)

7. In an experiment to investigate the solubility of Y and Z, The following results were obtained:

Temperature (oC) 0 10 20 30 40 50

Solubility of solid Y 8 13 24 38 61 98
(g/100g of water)
Solubility of solid Z 28 32 35 38 42 46
(g/100g of water)

a) What do you understand by the term solubility? (1mk)

b) On the graph paper provided, plot a graph of solubility of Y and Z against temperature. (4mks)

c) From your graph determine:

I) The solubility of Y at room temperature 25oC (1mk)

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 II) The temperature at which solubility of Y is 45g/100g of water. (1mk)

d) If a solution of Y contains 35g of solid in 100g of water is cooled from 40oC, Determine:
I) The temperature at which the crystals will first form

II) The mass of crystals deposited if the solution is cooled at 5oC (1mk)

e) Compare the solubilities of Y and Z in water. (2mks)

f) Give one application of solubilities. (1mk)

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