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KCSE CLUSTER TESTS 15

Chemistry Paper 2

1.

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

I. Write the electronic configuration for the ion formed by element B and D. B............................................................................................................................. (1mk) D............................................................................................................................. (1mk)

II. Select an element which is

i) The most reactive non metal (1mk)

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ii) A poor conductor of electricity. (1mk)

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b) In which period of the periodic table does element E belong? (1mk)
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c) element E loses its outermost electron more readily than A. Explain (1mk) ................................................................................................................................ ................................................................................................................................

d) Using dots (.) and crosses (x) to represent the outermost electrons, show bonding in the compound formed by elements C and D. (2mks)

e) Explain why the melting point of element B is higher than A. (2mks) ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................

g) Describe how a sold mixture of the sulphate of element R and lead sulphate can be separated into solid samples. (3mks) ................................................................................................................................ ................................................................................................................................ ................................................................................................................................

13 marks

2.

a) With the aid of a chemical equation, explain how boiling affects water hardness. (2mks)

b) The saturated point of sodium nitrate in 100g of water is given for various temperatures in 0C.

i) Plot a graph of saturation point of sodium nitrate against temperature. (3mks)

ii) Using the curve, determine the solubility at 700C. (1mk)


i) 100 grams of solution of sodium nitrate is in saturated conditions at 100c. How many grams of the salt will have to be added to make the solution just saturated at 800C (2mks)

ii) State one application of solubility (1mk)

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c) The graph below is a plot of concentration against time for a given reaction.

a) What is represented by curve A? Explain. (2mks)

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b) Explain why curve A rises fast then remain constant. (1mk)

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c) What does point P represent on the graph? (1mk)

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13 marks

3.

Crude oil is the main source of organic compounds such as hydrocarbons. The hydrocarbons in the crude oil have to be separated. a) Name four important hydrocarbons obtained from crude oil. (2mks)

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b) Give two uses of any two hydrocarbons in 3(a) above. (2mks)

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c) Give the meaning of the following terms.

I. Catalytic cracking (1mk)

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II. Thermal cracking (1mk)

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d) Study the following reaction scheme and answer the questions that follow

Name:

i) Colourless gas A ( ½ mk)

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ii) Product B ( ½ mk)

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iii) Gas D ( ½ mk)

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iv) Liquid E ( ½ mk)

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e) Write balanced equations for the reactions taking place in step I, II and III above. (3mks)


f) Name the type of reaction taking place in step I and II (1mk)

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g) State the importance of the reaction taking place in step II. (1mk)

14 marks

4.

The diagram below represents an incomplete set-up of apparatus that can be used to prepare and collect dry carbon (iv) oxide gas. Complete the diagram and answer the questions that follow.

I. a) Complete the above diagram (2mks)

b) Identify liquid R. (1mk)

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c) Write the equation for the reaction taking place in the flask S (1mk)

d) Explain why it is not advisable to use lead (II) carbonate in place of marble chips (1mk) .................................................................................................................................................... ....................................................................................................................................................

II. The diagram below is used to investigate the effect of carbon (II) oxide on Lead (II) oxide. Study it and answer the questions that follow.

8 marks

5.

The diagram below shows a set- up of apparatus that can be used to prepare nitrogen (IV) oxide. Study it and use it to answer the questions that follow

a) i) Write the equation for the reaction that takes place in the boiling tube. (1mk)

ii) State the observations made in the boiling tube. (2mks) .................................................................................................................................................... ....................................................................................................................................................

iii) Explain why lead (II) nitrate is preferred over other metal nitrates in this experiment. (2mks) .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... ....................................................................................................................................................

iv) Describe how gas A can be identified. (1mk)

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b) i) Name liquid B (1mk)

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ii) Write a chemical equation to show how liquid B is formed in this experiment. (1mk)

c) i) In another experiment excess aqueous lead (II) nitrate solution was reacted with a solution which contained 2.34g of sodium chloride. Calculate the mass of precipitate formed in this reaction. (Pb=207, Cl=35.5, Na=23) (2mks)

ii) Derive the ionic equation for the reaction that takes place when nitrogen (IV) oxide reacts with aqueous sodium hydroxide. (1mk)
.................................................................................................................................................... ....................................................................................................................................................

11 marks

6.

The flow chart below shows a sequence of reactions starting with iron. Use the chart to answer the questions that follow.

i) Name the reagent and state the conditions for step I (2mks) .................................................................................................................................................... ....................................................................................................................................................

ii) Name the following solid I) Solid S (1mk)

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II) Solid U (1mk)

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III) Solid T (1mk)

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IV) Write an ionic equation for the reaction which take place in step 3 (1mk)


V) Name one other substance that could be used instead of sodium hydroxide in step 3. (1mk) ...................................................................................................................................................

b) Give the name of the reagent which when reacted with concentrated hydrochloric acid produce chloride gas. (1mks)

i) Explain why it is necessary to pass chlorine gas through the apparatus before heating begins? (1mk) ............................................................................................................................................................ ............................................................................................................................................................

ii) Calcium oxide would be preferred to calcium chloride in the guard tube (1mk) ............................................................................................................................................................ ............................................................................................................................................................

iii) What property of iron (III) chloride makes it possible to be collected as shown in the diagram (1mk) ............................................................................................................................................................ ............................................................................................................................................................

iv) Write an equation for the chemical reaction that took place in the guard tube (1mk) ............................................................................................................................................................ ............................................................................................................................................................

12 marks

7.

The diagram below shows a set- up of apparatus that was used to prepare hydrogen gas.

a) Explain the observations that would be made if calcium turnings were used instead of zinc granules in the above experiment (2mks) ............................................................................................................................................................ ............................................................................................................................................................

b) i) Explain how liquid L can be identified by chemical means. (2mks) ............................................................................................................................................................ ............................................................................................................................................................

ii) How could the purity of liquid L be confirmed? (1mk) ............................................................................................................................................................ ............................................................................................................................................................

c) During this experiment, 100cm3 of XM suphuric acid was reacted. The volume of the gas produced was found to be 480cm3. Determine the value of x, the concentration of the acid in moles per litre. (1 mole of gas occupies 24000cm3 at R.T.P) (2mks)

9 marks

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