Q.With one example, explain roasting.

Roasting converts a sulphide ore into its oxide by heating in air; e.g. ZnS -> ZnO.

Roasting is the process of heating a concentrated ore (usually a sulphide) strongly in the presence of an excess (regular supply) of air, at a temperature below the melting point of the metal. The ore is converted into its oxide, and volatile impurities and gases such as SO2 escape.

Example - roasting of zinc blende (ZnS):

2ZnS + 3O2 --(heat)--> 2ZnO + 2SO2

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