Question

A zinc ore on heating in air forms sulphur dioxide. Describe briefly any two stages involved in the conversion of this concentrated ore into zinc metal.

Answer 1

Roasting: Zinc blende ore is roasted, i.e., heated in the presence of excess air. This converts zinc sulphide ore to zinc oxide. The reaction involved is.

\[\ce{\underset{(Zinc blende ore)}{\underset{Zinc sulphide}{2ZnS_{(s)}}} + \underset{(From air)}{\underset{Oxygen}{3O2_{(g)}}} ->[Roasting] \underset{Zinc oxide}{2ZnO_{(s)}} + \underset{Sulphur dioxide}{2SO2_{(g)}}}\]

Reduction: Zinc metal is extracted by the reduction of its oxide with carbon (or coke). Thus, when zinc oxide is heated with carbon, zinc metal is produced.

\[\ce{\underset{Zinc oxide}{ZnO_{(s)}} + \underset{(Reducing agent)}{\underset{Carbon}{C_{(s)}}} -> \underset{Zinc metal}{Zn_{(s)}} + \underset{Carbon monoxide}{CO_{(g)}}}\]