In order to obtain 1 tonne of aluminium, 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite is required. 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. When bauxite is treated with sodium hydroxide solution, what happens to (i) the aluminium oxide (ii) the iron (III) oxide
Solution: (i) The aluminium oxide forms sodium aluminate.
(ii) The iron (III) oxides does not dissolve in NaOH and is removed by filtration.