Question

How is zinc extracted from its carbonate ore (calamine)? Explain with equations.

Answer 1

Calcination is the process in which a carbonate ore is heated strongly in the absence of air to convert it into metal oxide.

Zinc is found as a sulphide in the ore zinc blende (ZnS). To extract zinc metal from zinc sulphide, it must first be transformed into zinc oxide. This is obtained through roasting. Upon strong heating of zinc blende ore (zinc sulphide) in air (roasting), zinc oxide and sulphur dioxide are produced.

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

Thus, roasting converts zinc sulphide into zinc oxide.