Identify the substance oxidised and substance reduced in the following reactions :
(i) `ZnO(s) + C(s) to Zn(s) + CO(g)`
(ii) `2Na(s) + O_(2)(g) to 2Na_(2)O(s)`
(iii) `CuO (s) + H_(2)(g) to Cu(s) + H_(2)O(l)`.

Explanation

(i) C is oxidised to CO and ZnO is reduced to Zn.
(ii) Na is oxidised to `Na_(2)O` and `O_(2)` is reduced.
(iii) `H_(2)` is oxidised to `H_(2)O` and CuO is reduced to Cu.