For each of the substance listed below, describe the role played in the extraction of aluminium. (1) Cryolite (2) Sodium hydroxide (3) Graphite.

Explanation

(1) Cryolite acts as a solvent for the electrolytic mixture and also lowers the fusion temperature from `2050^(@)C` to `950^(@)C` which saves electrical energy
(2) Sodium hydroxide is used to remove insoluble impurities from the ore. When bauxite ore is treated with sodium hydroxide, it dissolves and forms sodium aluminate leaving behind insoluble impurities called red mud (consists of ferric oxide, sand etc.)
(3) Graphite is used as an electrode in the extraction of aluminium because it has a very high melting point and is a good conductor of electricity.