Question

When limestone is heated, carbon dioxide gas​ is given off. The metallurgical operation is :
A. Smelting
B. Reduction
C. Calcination
D. Roasting

Answer 1

Hint: Calcination is a process of preparing metal ores. In this process metal carbonate is heated to form metal oxide along with carbon dioxide gas.

Complete Step by Step Answer:
Limestone is a carbonate compound of calcium that is calcium carbonate.
Calcination is defined as the thermal treatment of a solid chemical compound, mainly carbonate compound of a metal, that is heated at high temperature without melting under restricted supply of ambient oxygen gas. This process is generally used for the purpose of removing impurities or the volatile substances or to active thermal decomposition.
In this reaction calcium carbonate is heated to form calcium oxide along with carbon dioxide gas.
The reaction can be given as follows-
$CaC{{O}_{3}}\to CaO+C{{O}_{2}}$
In this reaction one mole of calcium carbonate is heated to form one mole of metal oxide ore that is calcium oxide along with carbon dioxide gas.
Thus we can say that when limestone is heated, carbon dioxide gas​ is given off. The metallurgical operation is calcination.
Thus the correct option is C.

Note: On heating limestone or calcium carbonate decomposes to calcium dioxide and carbon dioxide gas. In this reaction heat is needed so, it is a endothermic reaction.