Question

Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as:
(A) Smelting
(B) Ore dressing
(C) Calcination
(D) Bessemerisation

Answer 1

Hint: All the given processes are used in the extraction of metals from their ores. When the ore is heated in a limited supply of air or absence of air at a temperature just below its melting point causes thermal decomposition, phase transition and removes volatile components of the ore.

Complete Step by step answer: The thermal treatment in presence of air applied to metals to achieve warm deterioration of the unstable parts is known as calcination.
Calcination occurs at the temperatures below the softening or melting temperature of the ores.
Calcination is carried out in a reverberatory furnace and the holes of the furnace are kept closed. Calcination is used for carbonate and hydroxide ores.
For example, consider calcination of limestone. When limestone is calcined, it converts to calcium oxide and along with it carbon dioxide gas is released. The reaction is as follows:

${\text{CaC}}{{\text{O}}_{\text{3}}}\xrightarrow{{{\text{Calcination}}}}{\text{CaO}} + {\text{C}}{{\text{O}}_{\text{2}}}$

Thus, heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as calcination.

Thus, the correct option is (C) calcination.

Note: 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 grains are mechanically separated from the ore to produce a concentrate is known as ore dressing.
The process in which air is blown to molten copper to produce metallic copper is known as bessemerisation.