Question

Giving example, differentiate between roasting and calcination.

Answer 1

Differentiation

Roasting	Calcination
Ore is heated in presence of excess air or oxygen	Ore is heated in absence or in limited air or Oxygen.
Used in sulphide ore.	Used in Carbonate ore.
SO₂ is produced along with metal oxide.	CO₂ is produced along with metal oxide.

Example of roasting :

$$\begin{gathered} 2ZnS+3O_2\to 2ZnO+2S{O}_{2 \\ } \\ 2PbS+3O_2\to 2PbO+2S{O}_{2 \\ } \\ 2Cu₂S+3O_2\to 2C{u}_{2}O+2S{O}_{2 \\ } \end{gathered}$$

Example of calcination:
$$\begin{gathered} F{e}_2{O}_3.2H_{2}O\to Fe2O3\left(s\right)+x{H}_{2}O\left(g\right) \\ ZnC{O}_3\to ZnO\left(s\right)+C{O}_2\left(g\right) \\ CaC{O}_3+M_{g}C{O}_3\to CaO\left(s\right)+M_{g}O\left(s\right)+2C{O}_2\left(g\right) \end{gathered}$$

Thus, in calcination compounds are heated in absence of air or oxygen whereas in roasting air or oxygen is present at the time of heating.