(a) Outline the procedures for the treatment of water for town supply. (b) (i) State...
(a) Outline the procedures for the treatment of water for town supply.
(b) (i) Statetwo main impurities present in bauxite.
(ii) Giveone reason why bauxite is usually preferred as the ore for the extraction of aluminium.
(iii) Outline the manufacture of aluminium form purified bauxite.
(c) (i) Explainbriefly the termfine chemical industry.
(ii) Statetwo differences between afine chemical and a heavy chemical.
(d) (i) Write a balanced chemical equation for the combustion of coal.
(ii) If 5.4 g of coal is burnt completely, calculate the amount of oxygen measured at s.t.p. that would be required for the combustion.
[C = 12.0, O = 16.0, Molar volume of a gas at s.t.p. = 22.4 dm\(^3\)]
(e) Nametwo substances which can be used as electrodes during the electrolysis of acidified water.
Explanation
(a)
- addition of alum / addition of coagulating agent
- sedimentation
- filtration
- disinfection / chlorination / addition of chlorine
(b) (i) - iron (III) oxide
- silicon (IV) oxide / sand
- trioxosilicates (IV)
(ii) because aluminium oxide has too high a melting point to eletrolyse on its own /bauxite has low silica content
(iii) - Alumina and molten cryolite
- Melted and electrolysed
- Cell with carbon electrodes
- Molten aluminium produced at the base of cell.
- siphoned off / removed at the base
(c) (i) A fine chemical industry is the one that manufactures chemicals in smaller
quantities / amounts for specific use with high level of purity
(ii)
| Fine chemical | Heavy chemical |
- they are produced in smaller quantities | - they are produced in larger &nb |