Question

Usually ______ (sulphide/carbonate) ores are subjected to ______ (calcination/roasting) which is done in the absence of air.

Answer 1

Usually carbonate ores are subjected to calcination which is done in the absence of air.

Explanation:

Carbonate ores are heated in the absence of air to convert them into oxides, e.g., $$\mathrm{ZnCO_3 \rightarrow ZnO + CO_2}$$.