Question

The following questions are related to the extraction of aluminum by electrolysis. (i) Name the other aluminum-containing compound added to alumina and state its significance. (ii) Give the equation for the reaction that takes place at the cathode. (iii) Explain, why is it necessary to renew the anode periodically?

Answer 1

1. The other aluminium containing compound added to alumina is cryolite. For alumina, it acts as a solvent. It also decreases the fusion temperature from 2050 degrees to 950 degrees and enhances the conductivity.
2. The reaction that takes place at the cathode is, ${\mathrm{Al}}^{3+}+3\mathrm{e}\to \mathrm{Al}$.
3. At the anode, oxygen gas is formed during the electrolysis process. The oxidizing of the graphite anode produces carbon dioxide. So, it is important to replace the anode periodically.

Therefore, the answers are:

1. Cryolite
2. ${\mathrm{Al}}^{3+}+3\mathrm{e}\to \mathrm{Al}$
3. At the anode, oxygen gas is formed during the electrolysis process. The oxidizing of the graphite anode produces carbon dioxide. So, it is important to replace the anode periodically.