(a)(i) Explain briefly the term chemical industry. (ii) State three factors that should be considered in siting a chemical industry. (b)(i) Describe briefly...

Answer Details

(a)(i) A chemical industry is an industry that uses chemical reactions and processes to convert raw materials into useful finished products on a large (commercial) scale.

(a)(ii) Three factors to consider in siting a chemical industry: availability of raw materials, a cheap and adequate source of energy/power and water, and good transport and nearness to the market (availability of labour and safe waste disposal are also acceptable).

(b)(i) Extraction of tin

Tin is obtained from its ore cassiterite, \(SnO_2\). The ore is first concentrated by washing (froth flotation/gravity), then reduced with carbon (coke) in a furnace: \[SnO_2 + 2C \to Sn + 2CO\] The molten tin is run off and refined.

(b)(ii) Two uses of tin: tin-plating (coating) of steel to make food cans, and making alloys such as solder and bronze.

(c)(i) Constituents of cement: limestone (\(CaCO_3\)), clay/shale (aluminosilicates), and a little gypsum (with silica and iron oxide).

(c)(ii) Mortar (slaked lime, sand and water) sets by absorbing carbon(IV) oxide from the air, forming hard calcium trioxocarbonate(IV): \[Ca(OH)_2 + CO_2 \to CaCO_3 + H_2O\]

(d)(i) Pollution is the introduction of harmful (unwanted) substances into the environment, making it unclean and injurious to living things.

(d)(ii) Two air pollutants: carbon(II) oxide (\(CO\)) and sulphur(IV) oxide (\(SO_2\)) (oxides of nitrogen and unburnt hydrocarbons are also acceptable).

(e) \(N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)};\ \Delta H = -92.37\ \text{kJ}\). This is the exothermic Haber synthesis of ammonia; a high yield is favoured by low temperature and high pressure, while an iron catalyst is used to reach equilibrium quickly. (No specific sub-question is stated for part (e).)