ICSE Class 10 Answered
Roasting: It is the process in which a sulphide ore is strongly heated in the presence of air to convert it into a metal oxide.
This is done in case of sulphide ores so as to remove sulphur in the form of SO2 and to obtained corresponding metal oxide.
So, roasting is not done for carbonate ores, moreover, calcination is more difficult than roasting.
It is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides.
So before reduction can be done, the ore is converted into metal oxide.