Question

What are the electrodes used in the extraction of aluminium?

Answer 1

Aluminium is extracted by electrolysis in Hall's electrolytic process.

1. During electrolysis, the negative electrodes (cathodes) and the positive electrodes (anodes) both are made of graphite, a form of iron.
2. Molten aluminium is produced at the cathode and oxygen gas is evolved at the anode.

$$\begin{gathered} {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{aq}\right)\stackrel{\mathrm{Electrolysis}}{\to }2{\mathrm{Al}}^{3+}\left(\mathrm{aq}\right)+3{\mathrm{O}}^{2-}\left(\mathrm{aq}\right) \\ \mathbf{At}\mathbf{}\mathbf{cathode}:2{\mathrm{Al}}^{3+}\left(\mathrm{aq}\right)+6{\mathrm{e}}^{-}\to 2\mathrm{Al}\left(\mathrm{s}\right) \\ \mathbf{At}\mathbf{}\mathbf{anode}\mathbf{}:3\mathrm{O}\left(\mathrm{g}\right)+3\mathrm{O}\left(\mathrm{g}\right)\to 3{\mathrm{O}}_2\left(\mathrm{g}\right) \end{gathered}$$

Hence, Graphite electrodes are used in the extraction of aluminium.