Given below are the steps for extraction of copper from its ore. Write the reaction involved. 
(i) Roasting of copper (I) sulphide.
(ii) Reduction of copper (I) oxide with copper (I) sulphide.
(iii) Electrolytic refining
(b) Draw a neat and well labelled diagram for electrolytic refining of copper.

Explanation

(i) (a) Roasting : `2Cu_(2)S(s) + 3O_(2)(g) overset("heat")rarr 2Cu_(2)O(s) + 2SO_(2)(g)`
(b) Reduction : `2Cu_(2)O(s) + Cu_(2)S(s) overset("heat")rarr6Cu(s) + SO_(2)(g)`
This reaction in which one of the reactants `(Cu_(2)S)` carries the reduction of one of the products `(Cu_(2)O)` formed during the reaction, is known as auto-reduction.
(c ) Reactions taking place in electrorefensing are :
At cathode (reduction) : `Cu^(2+)(aq) + 2e^(-)rarr Cu(s)`
At anode (oxidation) : `Cu(s) rarr Cu^(2+)(aq) + 2e^(-)`