Question

Self-reduction of the sulphide ore takes place during:

• A. roasting
• B. smelting
• C. calcination
• D. cupellation

Answer 1

The correct option is A roasting

Self-reduction of the sulphide ore takes place during roasting.

Roasting consists of thermal gas-solid reactions, which can include oxidation, reduction, chlorination, sulphation, and pyrohydrolysis. In roasting, the ore or ore concentrate is treated with very hot air. This process is generally applied to sulphide minerals.

During roasting, the sulfide is converted to an oxide, and sulphur is released as sulphur dioxide, a gas. A blast of air converts $C{u}_{2}S$ partly into $C{u}_{2}O$ which reacts with remaining $C{u}_{2}S$ to give molten copper.