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Question
In the Hall's process for extraction of aluminium, Sate the location of cathode and anode and explain what occurs at each electrode.
Solution
Cathode is the inner lining of gas-carbon of the electrolytic cell and anode is the thick carbon rods dipping into the fused electrolytes.
At cathode: Aluminium ions get reduced as:
Al3+ + 3e- → Al
At anode: oxygen gas is liberated as:
O2- - 2e- → [O]
[O] + [O] → O2
The oxygen formed at anode oxidizes the carbon of the anode to carbon dioxide.
C + O2 → CO2
As a result the anode gets oxidized and it has to be replaced periodically.
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