Question

Assertion :Roasting is a process in which the ore is heated strongly in absence of air.
Reason: Concentration of sulphide ores is done by calcination.
A) Both assertion and Reason are correct and Reason is the correct explanation for Assertion
B) Both assertion and Reason are correct but Reason is not the correct explanation for Assertion
C) Assertion is correct but Reason is incorrect
D) Both Assertion and Reason are incorrect

Answer 1

‌ Metals are usually present in ores as hydrated oxides(hydroxides), carbonates and sulphides. Depending upon the nature of minerals present in ore, following two methods are used for conversion of ore to their respective oxides.Roasting is the process to convert sulphide ores into their respective oxides by heating strongly in the presence of excess air.Calcination is the process to convert the carbonate and hydrated oxide ores to their respective oxides by heating either in absence or in limited supply of air.

Complete answer:
Roasting is a process in which ore is heated strongly in presence of air. Hence, Assertion is incorrect.
Further, Concentration of sulphide ores is done by a process known as Froth Flotation. This method is based upon the fact that the surface of sulphide ores is preferentially wetted by oils while that of gangue is preferentially wetted by water. Hence, Reason is also incorrect.
The correct option is Option D i.e., Both Assertion and Reason are incorrect.

Additional Information: Concentration of ores is the removal of unwanted earthy and siliceous impurities(gangue) from the ore.

Note: Calcination is the process of heating the ore in absence of air while roasting is the process of heating the ore in the presence of air. We need to remember that Froth Floatation is the process used for the concentration of sulphide ores. It is based upon preferential wetting of ore particles by oil and gangue particles by water.