Question

In the Hall-Heroult process, aluminum is formed at the cathode. The cathode is made out of
1. Platinum
2. Carbon
3. Pure aluminum
4. Copper

Answer 1

Correct Answer - Option 2 : Carbon

Concept:

In Hall-Heroult’s process, aluminium is formed at the cathode. The cathode is made out of carbon. In this method, Al₂ O₃ is melted with crylite, Na₃ [AlF₆] and electrolyzed in a graphite lined steel tank, which serves as the cathode. The anode is also made of graphite.

The cell runs continuously and at intervals, molten aluminium is drained from the bottom of the cell and more bauxite is added. The electrolytic reaction is as follows:

At cathode: Al³⁺ + 3e^- → Al

At anode:

C (s) + O^2- (melt) → CO (g) + 2e^-

C(s) + 2O^2- (melt) → CO₂ (g) + 4e^-