Describe the principle controlling each of the following processes :
Electrolytic refining of metals.

Explanation

The impure metal is made the anode. A strip of the same metal in pure form is taken as cathode. They are immersed in an electrolytic bath containing soluble salt of the same metal. Metals like copper and zinc are refined using this method. The reactions involved may be written as :
Anode : `M to M^(2+) +2e^(-)`
Cathode : `M^(n+) +n e^(-) to M`.