Question 18

What is the role of graphite rod in the electrometallurgy of aluminium?

Answer

In the electrometallurgy of aluminium, a fused mixture of purified alumina (Al2O3), cryolite (Na3AlF6) and fluorspar (CaF2) is electrolysed. In this electrolysis, graphite is used as the anode and graphite-lined iron is used as the cathode. During the electrolysis, Al is liberated at the cathode, while CO and COare liberated at the anode, according to the following equation.

If a metal is used instead of graphite as the anode, then Owill be liberated. This will not only oxidise the metal of the electrode, but also convert some of the Al liberated at the cathode back into Al2O3. Hence, graphite is used for preventing the formation of Oat the anode. Moreover, graphite is cheaper than other metals.

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