Q. In order to obtain 1 tonner of aluminium, the following inputs are required. 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is Iron (III) oxide. Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite.
(a) When bauxite is treated with sodium hydroxide solution, what happens to:
(i) the aluminium oxide,
(ii) the iron (III) oxide?
(b) (i) Name the process used for the purification of bauxite.
(ii) Write the equation for the action of heat on aluminium hydroxide.
(c) (i) Write the formulae of cryolite.
(ii) Write down the word which correctly completes the following sentence.By dissolving aluminium oxide in cryolite a ..........(conducting/non conducting) solution is produced.
(iii) Why is so much graphite required for the electrolytic process?
(iv) Write the equation for the reaction which takes palace at cathode.
