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KCSE CLUSTER TESTS 16

Chemistry Paper 2

1.

Study the information in the table below which shows the periodic properties of certain elements. The letters do not represent the actual symbols of the element.

a) Give the period and group to which element P belongs:

Group..............................................................................................

Period...............................................................................................

b) Using dots (.) and crosses (x) to represent electrons show the bonding in a compound formed between Q and R. .................................................................................................................................................... ...................................................................................................................................................

c) Compare and explain the reactivity of elements P and Q with water.

.................................................................................................................................................... ................................................................................................................................................... .................................................................................................................................................... ...................................................................................................................................................

d) Explain why the atomic radius of R is smaller than its ionic radius.

.................................................................................................................................................... ...................................................................................................................................................

e) Write down the electronic arrangement of the atom of:

P.....................................................................................................................

S.....................................................................................................................

f) Identify two elements that belongs to the same period.

.................................................................................................................................................... ...................................................................................................................................................

g) What name is given to the group of elements where R belongs?

.................................................................................................................................................... ...................................................................................................................................................

h) Element P reacts with water at stp to produce 0.224dm3 of gas. Determine the mass of P which was reacted with water. (Molar gas volume at stp =22.4dm3, Relative atomic mass of P =24).

.................................................................................................................................................... ...................................................................................................................................................

10 marks

2.

a) The flow chart below is a summary of fractional distillation of liquid air.

i) Explain how carbon (IV) oxide gas is removed in step I
...................................................................................................................................................

ii) State the form in which F is removed.

....................................................................................................................................................

iii) Identify the products D, E and F

D..............................................................................................

E..............................................................................................

F...............................................................................................

iv) Explain how the dust particles are removed.

.................................................................................................................................................... ...................................................................................................................................................

v) Describe how one can distinguish a gas jar full of carbon (IV) oxide from oxygen. .................................................................................................................................................... ...................................................................................................................................................

vi) Give two commercial uses of carbon (IV) oxide

.................................................................................................................................................... ...................................................................................................................................................

vii) State one use of substance E

....................................................................................................................................................

viii) Describe the process by which Nitrogen is obtained from air on a large scale. .................................................................................................................................................... ...................................................................................................................................................

12 marks

3.

Use the standard electrode potentials given below to answer the questions that follow

a) Select two half cells which when combined give the lowest workable cell potential

.................................................................................................................................................... ...................................................................................................................................................

b) Calculate the emf for cell formed by combining the two half cells in (a) above. .................................................................................................................................................... ...................................................................................................................................................

c) Using the half reactions listed above, select i) the strongest oxidizing agent. .................................................................................................................................................... ...................................................................................................................................................

ii) the strongest reducing agent

.................................................................................................................................................... ...................................................................................................................................................

d) The set up below was used to study the reaction between silver nitrate solution and copper metal.

i) After a few minutes, lustrous crystals of silver are formed on the copper spiral. Write down the ionic equation to confirm this. ....................................................................................................................................................

ii) State the observation made in the solution after the set up was left overnight. .................................................................................................................................................... ...................................................................................................................................................

iii) If the above set up involved the ions of element W and metal X, use the electrode potentials given above to calculate the emf of the cell. .................................................................................................................................................... ...................................................................................................................................................

e) A current of 0.75A was passed through the solution for 1 hour and 4 minutes. The mass of metal R deposited on the jug was 0.52g. (IF=96500C, R=52). i) Calculate the quantity of electricity passed

.................................................................................................................................................... ...................................................................................................................................................

ii) How many moles of metal R were deposited?

.................................................................................................................................................... ...................................................................................................................................................

iii) Calculate the quantity of electricity required to deposit two moles of metal R. .................................................................................................................................................... ...................................................................................................................................................

iv) Calculate the number of faradays required to deposit 52g of metal R. .................................................................................................................................................... ...................................................................................................................................................

v) Determine the charge on the ion metal R.

.................................................................................................................................................... ...................................................................................................................................................

10 marks

4.

a) The diagram below is a set up to prepare ethyne gas.

i) Name the reagents used in the above reaction.

Solid B........................................................................................................................

Liquid A ....................................................................................................................

ii) Write an equation for the reaction taking place between liquid A and solid B .................................................................................................................................................... ...................................................................................................................................................

iii) What property of the gas enables it to be collected as shown above. .................................................................................................................................................... ...................................................................................................................................................

iv) State the main commercial use of ethyne.

.................................................................................................................................................... ...................................................................................................................................................

b) The scheme below represents some reactions of ethyne. Study it and answer the questions that follow.

ii) Draw the structural formula of compound P labeled above.

.................................................................................................................................................... ...................................................................................................................................................

iii) Name the reagents used in: I. Process R

............................................................................................................................................. .............................................................................................................................................

II. Step I

............................................................................................................................................. .............................................................................................................................................

iv) Name the polymer T

............................................................................................................................................. .............................................................................................................................................

v) State one use of polymer T

.............................................................................................................................................

c) Ethanol and ethanoic acid reacts according to the following equation under condition M and process N to form product Z.

Name

i) Condition M

.................................................................................................................................................... ...................................................................................................................................................

ii) Process N

.................................................................................................................................................... ...................................................................................................................................................

iii) Draw the structural formula of product Z.



iv) State one different between the above reaction and that of an acid and a hydroxide. .................................................................................................................................................... ...................................................................................................................................................

v) Butane is often used as the main component in domestic gas fuels. Calculate its heating value.

d) i) Explain the observation made when butane and butan– i-ol are separately added to acidified potassium dichromate (VI).


ii) State one application of the reaction indicated in d (i) above.

.................................................................................................................................................... ...................................................................................................................................................

12 marks

5.

Aluminium is extracted using the electrolytic cell represented by the diagram below:

a) Why is aluminium extracted by an electrolytic method?

.................................................................................................................................................... ...................................................................................................................................................

b) Name the electrodes labeled x and y

x...........................................................................................

y..........................................................................................

c) The chief ore from which aluminium is extracted is bauxite

i) Name two main impurities present in bauxite

.................................................................................................................................................... ...................................................................................................................................................

ii) Aluminium oxide is the main component in bauxite with a melting point of but the electrolysis of molten aluminium oxide is carried out at . Explain how this is achieved.

d) Write the equations for the reactions taking place at the

I. Cathode

.......................................................................................................................................

II. Anode

.......................................................................................................................................

e) One of the electrodes named in (b) above is replaced periodically which one and why? .......................................................................................................................................

.......................................................................................................................................

f) Duralmin (an alloy of aluminium and magnesium) is preferred to pure aluminium in the construction of aeroplane bodies. Give two properties of duralmin that are considered.

.......................................................................................................................................

........................................................................................................................................

12 marks

6.

a) The flow chart below represents the industrial manufacture of nitric (V) acid. Study it and answer the questions that follow:-

i) Describe what takes place in the catalytic chamber, stating conditions.

.......................................................................................................................................

.....................................................................................................................................

ii) Write an equation for the reaction in chamber R.

.......................................................................................................................................

.....................................................................................................................................

iii) Why does copper metal react with hot concentrated nitric (V) acid but does not react with hot hydrochloric acid? .......................................................................................................................................

.....................................................................................................................................

iv) The reaction in chamber R is exothermic. How can the yield be affected by cooling the apparatus? Explain .......................................................................................................................................

.....................................................................................................................................

b) The chart below represents two industrial processes and some properties and uses of the products.

Name

I. Zinc ore................................................................................................

II. Colourless crystals (IUPAC name) ....................................................
c) Write equations for the reactions in
i) Step I.........................................................................................................
ii) Step IV .....................................................................................................
d) Give two conditions needed for step II to occur.
.......................................................................................................................................

.....................................................................................................................................

9 marks

7.

a) Define a base .

.....................................................................................................................................

b) In the equation below, identify the species that is acting as an acid. Explain

.......................................................................................................................................

.....................................................................................................................................

c) Study the chart below and answer the questions that follow:

i) Identify the metal ions in solution K.

.....................................................................................................................................

ii) Name the white precipitate L

.....................................................................................................................................

iii) Give the formula of the complex ion M

.......................................................................................................................................

.....................................................................................................................................

iv) What type of reaction occur in step 2 ? Explain.

.......................................................................................................................................

.....................................................................................................................................

d) The following is tabulated results of two experiments carried out using two clean pieces of magnesium ribbon of the same length and mass when reacted with different acids of the same concentration and volume.

ii) Explain briefly the relationship between the curves and the concentration of H+ ions(aq) in both acids. .......................................................................................................................................

.....................................................................................................................................

.......................................................................................................................................

....................................................................................................................................

e) i) Name two substances that cause permanent hardness.

.......................................................................................................................................

.....................................................................................................................................

ii) Using an equation, show how boiling removes temporary hardness.

.......................................................................................................................................

.....................................................................................................................................

14 marks

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