The Various steps involved are:
(i) Concentration : The ore is crushed and then concentrated by froth floatation process.
(ii) Roasting : The concentrated ore is heated in the presence of excess of air at about 1200 K to form zinc oxide.
\(\underset{\text{zinc blends}}{2ZnS} + 3O_2\xrightarrow{\text{Heat}} \underset{\text{zinc oxide}}{2ZnO} + 2SO_2\)
(iii) Reduction : ZnO obtained above is mixed with powered coke and heated to 1673 K in a fire clay retort. It is reduced to zinc metal.
\(ZnO + C \xrightarrow{1673 K}Zn + CO\)
(iv) Electrolytic refining : Impure zinc is made of anode
and cathode consists of a sheet of pure zince. The electrolyte consists of \(ZnSO_4\) solution acidified with dil. \(H_2SO_4\) On passing electric current, pure zinc gets deposited on the cathode.
Zinc is more reactive than hydrogen and it displaces hydrogen from acids. Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas is evolved.
The reaction will take place as:
\(Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4 (aq) + H_2(g)\)
