### Chemistry Past Questions

3691

Distinguish between cracking and reforming. Of what importance are the two processes in the petroleum industry?

3692

State Gay-Lussac's law and illustrate the law with one chemical reaction.

3693

(a) Explain with equation where appropriate, the functions of the following substances in the Solvay Process:

(i) limestone,

(ii) ammonia,

(iii) brine.

(b) Explain why the reaction between aqueous sodium trioxocarbonate (IV) solution and dilute hydrochloric acid is a neutralization reaction.

(c) Calculate the mass of sodium trioxocarbonate (IV) produced by the complete decomposition of 16.8g of sodium hydrogen trioxocarbonate (IV) (H = 1, O = 16, Na = 23, S = 33)

3694

(a) Explain why transition metals

(i) have high melting points

(ii) have variable oxidation states,

(iii) exhibit paramagnetism

(b) (i) Name the impurities present in bauxite

(ii) State how the impurities in bauxite are removed

(ii) Explain why aluminium oxide is said to be amphoteric.

(c) (i) Describe the electrolysis of copper (II) tetraoxosulphate (VI) solution, using copper electrodes.

(ii) Will the colour of the copper (II) tetraoxosulphate (VI) solution change at the end of the electrolysis described in (c)(i) above? Give reasons for your answer.

3695

(a) Write the structural formula of:

(i) 2, 2, 4 - trimethylpentane, (ii) ethylmethanoate, (iii) trans 2, 3 - dimethylbut - 2-ene.

(b) Write the structure of the straight-chain compound that is isomeric with 2,2,4 - trimethylpentane.

(c) Write chemical equations to illustrate the oxidation of: (i) a secondary alkanol (ii) a dihydric alkanol.

(d) When-Crushed cassava was warmed with dilute hydrochloric acid, a sweet-tasting compound, D was obtained. When compcund D was treated with the enzyme, zymase and the mixture distilled a clear and colourleCsliduid, E was obtained. When liquid E was warmed with eth anoic acid i n the presence of a few drops of concentrated tetraoxosulphate (V1) acid, a compound F, with fruity smell was obtained

. (i)To what class of compounds does D belong?

(ii) Name E and F

(iii) Write the fun-ctional group in F

(iv) Write the equation for the reaction between E and ethanoic acid in the presence of concentrated tetraoxosulphate (VI) acid.

(v) Name the type of reaction that takes place between E and ethanoic acid.

(e) Arrange the followingcompounds in their correct order of increasing boiling points: CH$$_3$$CH$$_2$$CH$$_2$$OH, CH$$_3$$CH$$_2$$CH$$_2$$CH$$_2$$CH$$_2$$CH$$_3$$ and CH$$_2$$CH$$_2$$CH$$_2$$CH$$_3$$; Explain the order.