Question

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

Answer 1

1) Cryolite is used to reduce the fusion temperature. The melting point of fused alumina is ${2050}^{\circ }C$ but on addition of cryolite it is reduced to ${950}^{\circ }C$. It increases the mobility of the fused mixture by acting as a solvent. It increases the conductivity of the mixture.

2) Sodium hydroxide helps in the purification of impure bauxite. It converts the impure bauxite into sodium aluminate.

3) Graphite is used as anode as it easily reduces $A{l}_2{O}_3$.