Discuss the process of roasting with suitable example.

Explanation

(i) Roasting is the method, usually applied for the conversion of sulphide ores into their oxides.
(ii) In this method, the concentrated ore is oxidised by heating it with excess of oxygen in a suitable furnace below the melting point of the metal.
(iii) `2PbS + 3O_(2) overset(Delta)rarr 2PbO + 2SO_(2) uarr`
`2ZnS + 3O_(2) overset(Delta)rarr 2ZnO + 2SO_(2) uarr`
`2Cu_(2)S + 3O_(2) overset(Delta)rarr 2Cu_(2)O + 2SO_(2) uarr`
(iv) Roasting also removes impurities such as arsenic, sulphur phosphorous by converting them into their volatile oxides.
(v) Ex : `4As + 3O_(2) rarr 2As_(2)O_(3) uarr`
`S_(8) + 8O_(2) rarr 8SO_(2) uarr`
`P_(4) + 5O_(2) rarr P_(4)O_(10)uarr`