Question

(a) Write two equations to show the extraction of copper from its sulphide ore.
​(b) How will you refine copper? Draw a labelled diagram of the electrolytic cell used for the refining of copper.

Answer 1

(a)
(i) Concentrated copper sulphide ore is roasted in air, to give oxidized copper oxide.
$2{\mathrm{Cu}}_2\mathrm{S}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\stackrel{\mathrm{roasting}}{\to }2{\mathrm{Cu}}_2\mathrm{O}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right)$
Then in the absence of air, the copper oxide formed above reacts with the remaining copper sulphide to form copper metal and sulphur dioxide.
$2{\mathrm{Cu}}_2\mathrm{O}\left(\mathrm{s}\right)+{\mathrm{Cu}}_2\mathrm{S}\left(\mathrm{s}\right)\stackrel{\mathrm{heat}}{\to }6\mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)$

(ii)

Electrolysis of copper is done using copper electrodes. The crude copper serves as the anode while a thin sheet of pure copper serves as the cathode.
$$\begin{gathered} \mathrm{At}\mathrm{cathode}:{\mathrm{Cu}}^{+2}+2{\mathrm{e}}^{-}\to \mathrm{Cu} \\ \mathrm{At}\mathrm{anode}:\mathrm{Cu}\to {\mathrm{Cu}}^{+2}+2{\mathrm{e}}^{-} \end{gathered}$$

As anode dissolves away, the cathodes on which the pure metal is deposited grows in size.