Question 62
(i) Given below are the steps for extraction of copper from its ore. Write the reaction involved.
(a) Roasting of copper (I) sulphide.
(b) Reduction of copper (I) oxide with copper (I) sulphide.
(c) Electrolytic refining.

(ii) Draw a neat and well-labelled diagram for electrolytic refining of copper.

(i) (a) Roasting of sulphide ore:
$2{\text{Cu}}_2\text{S(s)}+3{\text{O}}_2\text{(s)}\stackrel{\text{Heat}}{\to }2{\text{Cu}}_2\text{O(s)}+2{\text{SO}}_2\text{(g)}$
(b) $2{\text{Cu}}_2\text{O(s)}+{\text{Cu}}_2\text{S(s)}\stackrel{\text{Heat}}{\to }6\text{Cu(s)}+{\text{SO}}_2\text{(g)}$

This reaction is known as auto-reduction.

(c) Reaction for electrolytic refining
At cathode:${\text{Cu}}^{2+}\text{(aq)}+2{\text{e}}^{-}\to \text{Cu(s)}$
At anode: $\text{Cu(s)}\to {\text{Cu}}^{2+}\text{(aq)}+2{\text{e}}^{-}$

(ii) Diagram for electrolytic refining of copper