(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 the chemical reactions taking place in the extraction of copper from Cu₂S.

Option (i)

Zone refining is used to obtain high purity semiconductor. The process involves the use of heat treatment along the axis of a semiconductor rod. The heat application is localised at small circumferential area and as the ring moves along the length the semiconductor melts and solidifies whereas the impurity is taken to the end of the length of the rod and is removed.

Option (ii)

Low boiling metals can be separated from an ore with the help of distillation process. Zinc and mercury can be separated from higher melting impurities using distillation process.

(b) The sulphide ores are generally roasted to obtain the component required element. Roasting is a process of heating of sulphide ores at high temperatures in presence of air. In case of copppr the following reactions are involved

This oxide can then be reduced into metallic copper with help of reduction with carbon or coking.