Question

Self reduction of sulphide ore takes place during:
A.Roasting
B.Smelting
C.Calcination
D.Cupellation

Answer 1

The process in which the hydrogen atoms are gained or the oxygen atoms are lost is known as reduction. Self-reduction means the species which undergoes reduction itself acts as a reducing agent.

Complete step by step answer:
The process in which the sulphide ores of less electropositive metals like copper, lead, etc. are heated in air to convert the ore to oxide or sulphate is known as self-reduction.
The self-reduction of sulphide ore occurs during the process of roasting.
The roasting of ore involves gas-solid reactions at higher temperatures. Roasting is done to purify the metal. Roasting involves oxidation, reduction, chlorination, sulphation and pyrohydrolysis.
During roasting, the ore is treated with air having high temperature.
When sulphide ore is roasted, the sulphide is converted to an oxide and along with it sulphur dioxide gas is released.

Thus, the correct option is option (A).

Additional Information:
The process in which the oxides obtained by roasting are reduced to the metal in its molten state is known as smelting. Rocky impurities associated with the ore are removed during smelting of the ore.
The process in which the concentrated ore is heated in a limited supply of air or in absence of air at the temperature just below the melting point of the ore is known as calcination.
The process in which the ore is treated under very high temperature in a cupel is known as cupellation. The couple is a flat, porous dish made up of a high temperature resistant material. Cupellation is used for processing of metals like gold and silver.

Note: The sulphide ore of copper ${\text{C}}{{\text{u}}_{\text{2}}}{\text{S}}$ when roasted partly converts to ${\text{C}}{{\text{u}}_{\text{2}}}{\text{O}}$. This ${\text{C}}{{\text{u}}_{\text{2}}}{\text{O}}$ reacts with the remaining ${\text{C}}{{\text{u}}_{\text{2}}}{\text{S}}$ and molten copper is obtained.