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2016 KCSE MOKASA Joint Examination

Chemistry Paper 1

1.

Explain the following:
(i) It is always advisable to scoop chemical substances using a clean spatula.
( ½ mark)
………………………………………………………………………………………………………………………….
(ii) Flammable substances should always be kept away from flames in the laboratory.
( ½ mark)
………………………………………………………………………………………………………………………….

1 marks

2.

Name one reagent that can be used to distinguish between Al3+ and Zn2+ ions in solution
and state what would be observed if each of the ions is treated with the reagent you have
named.
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3 marks

3.

Manganese sulphide reacts with acids according to the following equation.

State, giving a reason what would happen to the equilibrium if;
(i) Water is added to the equilibrium mixture. (1 ½ marks)
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(ii) Hydrogen chloride is bubbled into the equilibrium mixture. (1 ½ marks)
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3 marks

4.

Use the thermochemical equations below to answer the questions that follow.


(i) Draw an energy cycle diagram to show the enthalpy of formation of ethane.
(1 ½ marks)

(ii) Calculate the enthalpy of formation of ethane. (1 ½ marks)

3 marks

5.

State the conditions under which copper reacts with sulphuric acid and give an equation
for the reaction.
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2 marks

6.

When 8.8g of hydrocarbon Z was burnt in excess air, 14.4g of water and 11.95 dm3 of
carbon (IV) oxide were obtained at s.t.p. Determine the empirical formula of Z.

3 marks

7.

Perspex is a synthetic polymer of formula


(a) Write the structural formula of the monomer of Perspex. (1 mark)
(b) State the type of polymerization involved in the formation of perspex.
(1 mark)
……………………………………………………………………………………………………………………………………

2 marks

8.

When zinc granules are dropped into two separate solutions of dilute sulphuric (VI) and
concentrated sulphuric (VI) acid, effervescence of a colourless gas occurs in each case.
Give equations to represent the reactions that take place.
……………………………………………………………………………………………………………………………………
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2 marks

9.

Study the chart below and answer the questions that follow.


(a) Identity solid X. (1 mark)
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(b) Write an ionic equation for the reaction between P and copper (II) sulphide
solution. (1 mark)
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(c) State the observation made when gas P is bubbled through iron (III) chloride
solution. (1 mark)
……………………………………………………………………………………………………………………………………

3 marks

10.

Use the nuclear equations below to answer the questions that follow.

(i)
(ii)

(a) Give the actual names of particles X and Y. (1 mark)
X ………………………………………………………………………………………………
Y ………………………………………………………………………………………………
(b) Give the name of a radiation whose emission does not change the mass number
or the atomic number of a radioisotope. (1 mark)
…………………………………………………………………………………………………………………………

2 marks

11.

The structures below represent two cleaning agents M and P.

Which cleaning agent would be most suitable for use with water containing calcium
sulphate. Give a reason.
…………………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………………….

2 marks

12.

You are given the following half equations:


(i) Obtain an equation of the cell reaction. (1 mark)
…………………………………………………………………………………………………………………………………….
(ii) Calculate the value for the cell. (1 mark)
(iii) Give the oxidizing species. (1 mark)
…………………………………………………………………………………………………………………………………….

3 marks

13.

Using dots (●) and crosses (×) to represent outermost electrons; draw diagrams to show
bonding in:

(a) Aluminium chloride. (1 ½ marks)
(b) Sulphuric (IV) oxide. (1 ½ marks)

3 marks

14.

Use the information in the table below to answer the questions that follow.

Melting pointElementAtomic number
97.8R11
660S13
1440T14
-40.1U17
63.1V19


(a) Write the electron arrangement of: (1 mark)
(i) ion of S ……………………………………………….
(ii) atom of T ……………………………………………….

(b) Explain why the melting point of T is higher than that of U. (2 marks)
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3 marks

15.

Complete the table below.

3 marks

16.

The diagram below represents a set up used for the large scale manufacture of hydrochloric acid.

(a) Name substance X. (1 mark)
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(b) What is the purpose of the glass beads? (1 mark)
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(c) Give one use of hydrochloric acid. (1 mark)
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3 marks

17.

Calculate the volume of nitrogen (I) oxide produced when 38.2g of ammonium nitrate is
completely decomposed by heating (at s.t.p). (N = 14, H = 1, O = 16)

3 marks

18.

Give equations to show the reactions that take place when;
(a) iron reacts with steam. (1 mark)
…………………………………………………………………………………………………………………………………….
(b) Give one industrial use of the gas produced in the reactions in (i) and (ii) above.
(1 mark)
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2 marks

19.

(a) 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.
(2 marks)
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(b) Give the total number of atoms present in the gas produced when water is added
to magnesium nitrate. (1 mark)
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3 marks

20.

The graph below shows the behavior of a fixed mass of a gas at constant temperature.

(a) What is the relationship between the volume and the pressure of the gas?
(1 mark)
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(b) 60 cm3 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.), O = 16.0)
(3 marks)

2 marks

21.

State and explain the observation made when a moist red litmus paper is put in a gas jar
of dry chlorine gas.
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2 marks

22.

(a) When extinguishing a fire caused by burning kerosene, charbon (IV) oxide is
preferred to water. Explain. (2 marks)
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(b) Write the formula of the oxide of carbon which is ‘silent killer’. (1 mark)
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3 marks

23.

Explain why chlorine is a gas while iodine is a solid at room temperature.
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2 marks

24.

Apart from their location, state any two differences between a proton and an electron.
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2 marks

25.

What term is given to: The amount of energy given out when a neutral atom in gaseous
state gains an electron?
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1 marks

26.

A certain fertilizer is suspected to be containing nitrate ions. Describe how the presence
of nitrate ions can be determined in such fertilizer.
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3 marks

27.

Write balanced chemical equations to show the action of heat on the following nitrates.
(a) Lead (II) nitrate (1 mark)
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(b) Silver nitrate (1 mark)
…………………………………………………………………………………………………………………………………..

2 marks

29.

Starting with zinc carbonate solid describe how zinc hydroxide can be prepared in the
laboratory.
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3 marks

30.

Below is a scheme of some reactions starting with but-z-yne. Study it and answer the
questions that follow.


(a) Name Y, X and T (1 ½ marks)
Y ……………………………………………………………………………….
X ……………………………………………………………………………….
T ……………………………………………………………………………….
(b) Give the name of the following organic compounds. ( ½ mark)

2 marks

31.

The following results were obtained during an experiment to determine the solubility of
potassium nitrate in water at 300C. Mass of dish = 15.86g, mass of dish + saturated
solution at 30oC = 26.86g, mass of dish + solid KNO3 after evaporation to dryness = 16.7g. Calculate the mass of saturated solution containing 60.0g of water at 30oC.

2 marks

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