Describe the electrolytic reduction of alumina with neat labelled diagram

Explanation

i.The pure alumina obtained from bauxite ore by Bayer's process or Hall's process is electrolysed to obtain metallic aluminium.
ii. Alumina has a very high melting point `( gt 2000^@C)`.
iii. Electrolysis of alumina is carried out in an electrolytic cell at a much lower temperature by dissolving it in molten cryolite `(Na_3AlF_6)` and fluorspar `(CaF_2)`. Addition of cryolite and fluorspar reduces the melting point to about `1000^@C` .

iv.The electrolytic cell is a large steel tank having a lining of carbon (graphite) on the inner side. The carbon lining acts as cathode. A set of carbon (graphite) rods dipped in the molten electrolyte acts as anode .
v. On passing electric current, electrolysis of alumina takes place.
vi. Aluminium is formed at the cathode and oxygen gas is liberated at the anode .
vii.The electrode reactions are as follows :
Cathode: `Al^(3+) + 3e^(-) to Al_((l))` (Reduction)
Anode: `2O^(2-) to O_2 + 4e^(-)` (Oxidation)