Question

Differentiate between calcination and roasting.

Answer 1

Hint: The process of converting ore into an oxide by heating it strongly is called calcination. Roasting is the process where ore is converted into its oxide by heating it above its melting point in the presence of excess air.

Complete step by step answer:
Ores can be turned to metals only after converting carbonates and sulphides to an oxide ore. Through calcination or roasting, conversion of oxide is processed.

CALCINATION	ROASTING
Process in which ore is heated in the absence of air or supplied in small quantities is known as calcination.	Roasting is the process where ore is converted into its oxide. This process is done in the presence of excess air by heating it above its melting point.
During calcination moisture is pumped out from an ore.	During roasting moisture is present.
Calcination is used for carbonates and oxide ores.	Roasting is used for sulphide ores.
During calcination Carbon dioxide is given out.	During roasting a large amount of poisonous, metallic and acidic compounds are released.

Additional Information: In decomposition of limestone to lime and carbon dioxide, mostly the calcination process is used. Calcination is used in the removal of the ammonium ions in the synthesis of zeolites. Roasting process is generally applied to sulfide minerals. During roasting, oxide is converted from sulphide, and sulfur is released as sulfur dioxide (gas).

Note: Calcination and roasting are generally carried out in a reverberatory furnace. Remember that Calcination is used for carbonates and oxide ores while roasting (it is a metallurgical process) is used for sulphide ores.