Question

The process of heating an ore in the absence of air below its melting point is known as ……..
A. Calcination
B. Roasting
C. Smelting
D. Poling

Answer 1

When minerals and metallurgical ores are treated thermally, it transforms into materials which have several uses. The given method in the question is a method which is used in the purification process. This has been used in several industries.

Complete step by step answer:
Let’s focus on the given options first.
A. In calcination reaction, carbonates and hydroxides or hydrated oxides get converted to its oxides. This is done in limited supply of air or in absence of air at a temperature below its melting point. During this reaction, several components are expelled out like organic matter, volatile impurities, moisture etc. The mass which is remaining in it becomes porous. Sometimes, it is done to expel out the water molecule from hydrated oxides or carbon dioxide from carbonate ore.
Some examples are calcination of limestone, bauxite, iron etc.
B. Roasting is exactly the opposite of calcination. It is done in the absence of air. This is also undergone heating at a temperature below its melting point. Sometimes ores alone are heated but sometimes ores are combined with some materials and then heated.
Some examples are roasting of zinc sulfide, lead sulfide, copper sulfide etc.
C. Smelting is the process of heating a metal from its ores beyond its melting point. This is done in the presence of oxidizing agents or reducing agents.
D. Metals which have oxidized impurities are purified using a method known as poling. Copper or tin is purified from its copper ores or tin ores.
All the given methods are done in the presence of air except calcination. Thus the process of heating an ore in the absence of air below its melting point is known as calcination.

Hence, option A is the correct answer.

Note: We use a calcination process mainly to remove the volatile substances or make them in powder form. An example of the calcination process is given below. This shows the calcination process of zinc.
${{ZnC}}{{{O}}_3}\xrightarrow{\Delta }{{ZnO}} + {{C}}{{{O}}_2}$.