Write chemical reactions taking place in the extraction of zinc from zinc blende.
Write chemical reactions taking place in the extraction of zinc from zinc blende.

Solution 8:
The following processes are involved in the extraction of zinc from zinc blende:
(i) Concentration: Zinc blende ore is crushed and the concentration done by froth- floatation process.
(ii) Roasting: The concentrated ore is then roasted in presence of excess of air at about 1200 \mathrm{~K} as a result zinc oxide is formed.

    \[2 \mathrm{ZnS}+3 \mathrm{O}_{2} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{ZnO}+2 \mathrm{SO}_{2}\]

zinc blende zinc oxide
(iii) Reduction: Zinc oxide obtained above is mixed with powdered coke and heated to 1673 \mathrm{~K} in a fire clay retort where it is reduced ‘to zinc metal. \mathrm{ZnO}+\mathrm{C} \stackrel{1673 \mathrm{~K}}{\rightarrow} \mathrm{Zn}+\mathrm{CO}
At 1673 \mathrm{~K}, zine metal being volatile (boiling point 1180 K), distills over and is condensed.
(iv) Electrolytic refining: Impure zinc is made the anode while pure zinc strip is made the cathode. \mathrm{ZnSO}_{4} solution acidified with dil. \mathrm{H}_{2} \mathrm{SO}_{4} is the electrolyte used. On passing electric current, pure zinc gets deposited on the cathode.