Question

Differentiate roasting and calcination process giving one example of each

Answer 1

The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting. Roasting

2ZnS (s) + 3O2 (g) gives 2ZnO(s) + 2SO2 (g)

The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.

Calcination

ZnCO3 (s) gives ZnO(s) + CO2 (g)STEP FOLLOWED AFTER ROASTING/CALCINATION
The metal oxides are then reduced to the corresponding metals by using suitable reducing agents such as carbon. For example, when zinc oxide is heated with carbon, it is reduced to metallic zinc.

ZnO(s) + C(s) →Zn(s) + CO(g

Answer 2

Roasting is the process in which carbonate ores are converted into oxides in excess of oxygen.
Eg : from HgS, Hg can be yield and from ZnS, ZnO can be yield.

Calcination is a process in which Sulphide ores are converted into oxides in absence of oxygen or supply of oxygen in limited amount.
Eg : limestone