(i) Indicate the principle behind the method used for the refining of zinc.
(ii) What is the role of silica in the extraction of copper ?
(iii) Which form of iron is the purest on commercial scale ?

Explanation

(i) Zinc is refined by electrol-refining in which impure metal is converted into a block of anode and after electrolysis, pure zinc gets deposited at cathode.
(ii) Silica acts as an acidic flux and removes the basic impurity of iron oxide forming ferrous silicate (slag)
`underset(("Flux"))(SiO_(2))+ underset(("Impurity"))(FeO) to underset(("Slag"))(FeSiO_(3))`
Wrought iron is the purest variety or iron . It contains 0.2 to 0.5% carbon only.