(a) Name the method of refining which is
(i) used to obtain semiconductor of high purity,
(ii) used to obtain low boiling metal.
(b) Write chemical reactions taking place in the extraction of copper from Cu₂S.

(a) (i) Zone refining is the method, which is used to obtain the semiconductors like Si,               Ge and Ga in high purity.  

     (ii) This method is applicable for metals, such as Sn, Pb and Bi, which have low                      melting points as compared to their impurities.
$\begin{array}{r}\left(\mathrm{b}\right) 2{\mathrm{Cu}}_2\mathrm{S}+3{\mathrm{O}}_2\to 2{\mathrm{Cu}}_2\mathrm{O}+2{\mathrm{SO}}_2\\ {\mathrm{Cu}}_2\mathrm{O}+{\mathrm{Cu}}_2\mathrm{S}\to 6\mathrm{Cu}+{\mathrm{SO}}_2\end{array}$