(a) What is the difference between calamine and malachite? (b) Why is zinc used instead of Cu for recovery of Ag from [Ag(CN)₂]^- ? (c) What is the role of cryolite in metallurgy of Al?

OR

(a) Give two points of differences between pig iron and cast iron.

(b) Outline the principle of zone refining.

(a) The major difference between calamine and malachite is that calamine is zinc ore and malachite is copper ore.

(b) Zinc is a powerful reducing agent and readily displaces Ag which is present in the complex. Cu is also more reducing than Ag but is less effective than Zn. Moreover, zinc is cheaper than copper.

(c) Role of cryolite in metallurgy of Al is that it is mixed with purified alumina to reduce the melting point and to increase the fusibility.

OR

(a) The iron obtained from blast furnaces is known as pig iron. It contains around 4% carbon and many impurities such as S, P, Si, Mn in smaller amounts.
Cast iron is obtained by melting pig iron and coke using a hot air blast. It contains a lower amount of carbon (3%) than pig iron. Unlike pig iron, cast iron is extremely hard and brittle.
(b) The principle of zone refining is that the impurities in an ingot or ore of metal are more soluble in the melt state when compared to the corresponding solid state of the impurities. In the zone refining process, the impurities are concentrated at one end of the block of metal so that the rest of the block is purified.