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

Explanation

(i) The concentrated zinc blende ore (ZnS) is roasted in the presence of excess air at about 1200 K to convert it to zinc oxide .
`underset("Zinc blende")(2ZnS) + 3O_2 overset(Delta)to underset("Zinc oxide")(2ZnO) + 2SO_2`
(ii) Zinc oxide is reduced to zinc by heating with crushed coke at 1673 K .
`ZnO + C overset(1673K)to Zn + CO`
(iii) The impure copper is refined by electrorefining method. In this method, the impure zinc is made anode and a plate of pure zinc is made cathode in an electrodytic bath containing zinc sulphate and a small amount of dilute `H_2 SO_4` . On passing current , the following reactions occur :
At anode : `Zn to Zn^(2+) + 2e^(-)`
At cathode : `Zn^(2+) + 2e^(-) to Zn`
The zinc gets deposited on cathode and is collected.