Which of the following species is (are) desirable substance(s) in extraction of copper but not in extraction of iron ?

The zone refining of metal is based on the principle of

Vapour phase refining method is applicable on

Consider the following reactions at $1000\,^oC$

$(I)$ $Zn(s) + \frac{1}{2}{O_2}(g)\xrightarrow{\Delta }ZnO(g);{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} $      $\Delta {G^o} =  – 360{\mkern 1mu} \,kJ{\mkern 1mu} \,mo{l^{ – 1}}$

$(II)$ $C(s) + \frac{1}{2}{O_2}(g)\xrightarrow{\Delta }CO(g);{\mkern 1mu} {\mkern 1mu} $      $\Delta {G^o} =  – \,460{\mkern 1mu} \,kJ\,{\mkern 1mu} mo{l^{ – 1}}$

and choose the correct statement at  $1000\,^oC$

In electrorefining of copper, some gold is produced as