Give the reactions involved during the extraction of zinc from its ore by:
$(a)$ Roasting of zinc ore
$(b)$ Calcination of zinc ore

(N/A) Roasting is the process of heating a sulphide ore in the presence of excess air. The reaction for zinc sulphide $(ZnS)$ is:
$2ZnS(s) + 3O_2(g) \xrightarrow{\text{Heat}} 2ZnO(s) + 2SO_2(g)$
$(b)$ Calcination is the process of heating a carbonate ore in the absence or limited supply of air. The reaction for zinc carbonate $(ZnCO_3)$ is:
$ZnCO_3(s) \xrightarrow{\text{Heat}} ZnO(s) + CO_2(g)$