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KCSE CLUSTER TESTS 16

Chemistry Paper 1

1.

A certain element (Y) has atomic number 15 and mass number of 31.

i) Calculate the number of neutrons in the element. (1mk)


ii) Draw the ionic structure of the element. (1mk)


iii) How would the atomic size of the above element compare with another atom (X) whose atomic number is 11 and atomic mass 23? Explain (2mks) ........................................................................................................................................ ........................................................................................................................................

4 marks

2.

Lead II sulphate can be prepared by double decompositions.

a) What is meant by double decomposition? (1mk)

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b) Starting 1.0M sodium sulphate describe how you would prepare lead II sulphate solution. (2mks) ........................................................................................................................................ ........................................................................................................................................ ........................................................................................................................................ ........................................................................................................................................

3 marks

3.

a) Two gases X and Y have a relative density of 1.98 and 2.90gcm-3 respectively. They diffuse under the same conditions. If the relative molecular mass of Y is 64. Determine the relative molecular mass of X. (2mks)

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b) Under the same conditions carbon IV oxide, propane and nitrogen I Oxide diffuse at the same rate. Explain (1mk) ........................................................................................................................................ ........................................................................................................................................

3 marks

4.

The diagram below represents an incomplete set-up for preparation of dry sample of gas R


a) Complete the diagram to show how sample of gas R can be collected. (2mks)

b) Write a chemical equation for the reaction that produces gas R. (1mk)

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3 marks

5.

a) One of the use of sulphur IV oxide is bleaching wood pulp in industries. Explain why paper that is bleached with sulphur IV oxide turns colour to yellow when exposed to sunlight. (2mks)

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b) Name the products formed when sulphur IV oxide reacts with aqueous calcium hydroxide solution. (1mk) ........................................................................................................................................ ........................................................................................................................................

c) What is the significance of the reaction (b) above in the manufacture of sulphur VI acid? (1mk) ........................................................................................................................................ ........................................................................................................................................

4 marks

6.

Below is an equation for equilibrium reaction

What observations would be made if:

i) Temperature was raised. (1mk) .............................................................................................................................................

ii) Concentration is increased (1mk) ........................................................................................................................................ ........................................................................................................................................

2 marks

7.

a) The activity of a radioactive isotope decreases from 512 counts per minute to 64 counts per minute in 9 minutes.

What is the half – life of the radioactive Isotope? (2mks)

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b) Explain the difference between nuclear fission and nuclear fusion. (2mks)

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4 marks

8.

In the last stage of the Solvay process, a mixture of sodium hydrogen carbonate and ammonium chloride is formed.

i) State the method of separation used. (1mk) ........................................................................................................................................ ........................................................................................................................................

ii) Write an equation showing how lime is slaked (1mk) ........................................................................................................................................ ........................................................................................................................................

iii) Name the by- product recycled in the above process. (1mk) ........................................................................................................................................ ........................................................................................................................................

3 marks

9.

The structure below represents a polymer used in the manufacture of toys.

i) Draw and name the structure of the monomer. (1mk)


ii) Name the type of polymerization that occurs when forming the polymer. (1mk)

2 marks

10.

Chlorine can be prepared in the laboratory by oxidation of concentrated hydrochloric acid by lead IV oxide.

i) Give the condition necessary for the reaction above. (2mks)

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ii) Give a reason why the gas should be passed through water before collecting it. (1mk) ........................................................................................................................................ ........................................................................................................................................

iii) State the most suitable method for collecting dry chloride gas. (1mk) ........................................................................................................................................

4 marks

11.

a) Iron is usually extracted from its ores which are mainly haematite and magnetite. Name two impurities found in the ore. (1mk)

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b) State two roles of limestone in the extraction of iron. (2mks) ........................................................................................................................................ ........................................................................................................................................

3 marks

12.

The set below was used to collect the gas produced when zinc nitrate is strongly heated.

a) State two observations made in the test – tube. (2mks)

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b) Identify gas A (1mk)

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3 marks

13.

The table below shows the results obtained when a current of 2 amperes is passed through copper II sulphate solution for 15 minutes.

Calculate the quantity of electricity required to deposit one mole of copper (Cu =63.5) (3mks)

3 marks

14.

. a) What effect does impurities have on the melting point of substances? (1mk) ........................................................................................................................................

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b) State two application of the above phenomenon. (2mks)

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3 marks

15.

Compare the molar enthalpy of neutralization of hydrochloric acid with potassium hydroxide and that one of hydrochloric acid with ammonium hydroxide. Explain your answer. (2mks)

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2 marks

16.

Explain why when concentrated sulphuric VI acid is added to:

a) Sugar crystals, the crystals are charred to a black mass. (1mk)

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b) Old newspaper on printed on newsprint turns brown. (1mk)

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2 marks

17.

a) State Boyle’s Law. (1mk)

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b) On the axes below sketch a graph of pressure against volume

c) Explain the shape of the graph in terms of kinetic theory. (1mk)

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2 marks

18.

Two samples of hard water, A and B were boiled for some time and allowed to cool. Soap solution was stirred with each of the samples. Sample B readily formed lather with soap but sample A required much more soap to form lather. i) Write the formula of two salts likely to have caused hardness in each of the samples. (2mks)

I) Sample A .......................................................................................................................................

II) Sample B ........................................................................................................................................

ii) Which one of the water samples can be softened by using slaked lime? Explain (2mks) ........................................................................................................................................

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2 marks

19.

Industrially hydrogen can be obtained from the electrolysis of water to which sulphuric acid has been added.

i) Explain the role of sulphuric acid in the process. (1mk)

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ii) Write an equation for the production of hydrogen at the cathode. (1mk)

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2 marks

20.

Explain why hydrogen is obtained more rapidly when steam is reacted with heated magnesium than when magnesium is reacted with cold water. (2mks)

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2 marks

21.

The grid below is part of the periodic table, the number represent the atomic numbers of the elements in the grid.

On the grid indicate: a) M in the space with the most reactive metal. (1mk)


b) R in the space which could be occupied by an element capable of forming a compound M3R. (1mk)

2 marks

22.

Study the table below and answer the questions that follow:

Explain how the reducing power of the above metals changes from lithium to potassium (2mks) ........................................................................................................................................

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2 marks

23.

A mixture X contains three colourless substances which are: Alum, camphor and sugar. The solubility of these substances in the different solvents is as follows.

a) What is the quickest way of getting a pure sample of alum from the mixture? (2mks) ........................................................................................................................................

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b) How would you obtain a pure sample of sugar from the mixture above? (2mks) ........................................................................................................................................

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4 marks

24.

a) Explain what happens when chlorine gas is bubbled through a solution of hydrogen sulphide for some time. (1mk)

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b) Give an equation for the reaction taking place in the above reaction. (1mk)

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2 marks

25.

The table below shows the solubilities of salt A and B at different temperatures

a) If both A and B were present in 100cm3 of a saturated solution at 500c, what would be the total mass of crystals formed if the solution is cooled to 200c. (2mks)


b) A certain salt, C dissolves with absorption of heat from the surroundings. How would its solubility change with an increase in temperature. Explain (1mk)

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2 marks

26.

. Give the name and structural formula of the product formed when ethane gas reacts with:-

a) Bromine (1mk)

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b) Steam in the presence of phosphoric acid. (1mk)

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c) Hydrogen in the presence of platinum catalyst at 2000C. (1mk)

3 marks

27.

The following are standard electrode potentials for the given half –cells.

a) Which one of the above is the i) Strongest reducing agent? ( ½ mk)

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. ii) Strongest oxidizing agent? ( ½ mk)

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b) What would be observed when a zinc rod is dipped into a solution containing copper II ions? Explain using E

 values. (2mks)

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3 marks

28.

. Study the diagram below and answer the questions that follow.

a) Identify liquid Y (1mk)

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b) Write an equation for the reaction that takes place in the above set –up. (1mk) ........................................................................................................................................

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2 marks

29.

. a) Define the term amphoterism (1mk)

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b) Aluminium hydroxide is an amphoteric substance .

Write an equation to show how it reacts with sodium hydroxide solution. (1mk) ........................................................................................................................................

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c) 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.

Explain the difference on the volumes of the gas produced. (1mk)

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2 marks

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