Describe the underlying principle of each of the following processes :
(i) Recovery of silver from the solution obtained by leaching silber ore with a solution of NaCN
(ii) Electrolytic refining of crude metal.

Explanation

(i) N/A
(ii) Electrolytic refining : In this, method, the impure metal is made to act as anode. A strip of the same metal in pure form is used as Cathode. They are put in a suitable elecrtolyte both containing solulbe salt of the same metal. The more basic metal remains in the solutions and the less basic ones go to the anode mud. The rections are :
Anode : `M to M^(n+) + "ne"^(-)`
Cathode : `M^(n+) +" ne"^(-) to M`
Copper and zinc are refined by this method.