Question

Draw labelled diagram of Hall-Heroult Electrolytic cell for the extraction of aluminium. Write anode and cathode reactions.

Answer 1

Elemental aluminium can't be prepared by the electrolysis of an aqueous aluminium salt because hydronium ions easily oxidize elemental aluminium. Although a molten aluminium salt could be used instead of it, aluminium oxide has a melting point of ${2072}^{0}C$ so electrolysing it is impractical. In the Hall–Héroult process, alumina, $A{l}_2{O}_3$, is dissolved in molten synthetic cryolite, $N{a}_{3}Al{F}_6$, to lower its melting point for easier electrolysis.