Question

Consider the following statements: Roasting is carried out to :
(i) Convert sulphide to metal oxides and $S{O}_2$
(ii) Remove water of hydration
(iii) melt the ore
(iv) Remove arsenic and sulphur impurities

• A.
  (i), (ii) and (iii) are correct
• B.
  (i) and (iv) are correct
• C.
  (i), (ii) and (iv) are correct
• D.
  (ii), (iii) and (iv) are correct.

Answer 1

The correct option is C

(i), (ii) and (iv) are correct
Roasting is the process in which concentrated ore is heated to high temperatures in presence of excess of air. It will convert sulphides to metal oxides and $S{O}_2$ and remove arsenic and sulphur impurities and water of hydration.
Some of the reactions involving sulphide ores are:
$2ZnS+3O_2\to 2ZnO+2S{O}_{2}2PbS+3O_2\to 2PbO+2S{O}_{2}2C{u}_{2}S+3O_2\to 2C{u}_{2}O+2S{O}_2$
The sulphide ores of copper are heated in reverberatory furnace. If the ore contains iron, it is mixed with silica before heating.
Iron oxide ‘slags of ’ as iron silicate and copper is produced in the form of copper matte which contains $C{u}_{2}S$ and $FeS$.
$FeO+Si{O}_2\to FeSi{O}_3$