Question

Differentiate between roasting and calcination.

Answer 1

Hint: Both roasting and calcination are processes used in metallurgy. They are generally used to remove impurities from the metal ore. They are both thermal treatments provided to a meal ore.

Complete step by step answer:
 Even though both roasting and calcination are used for a similar purpose these two processes are very different from each other which we will discuss below-

ROASTING	CALCINATION
Ore is heated in regular or excess supply of air.	Ore is heated in absence of air.
Ore is heated at below the melting point	Generally used for carbonates and oxide ores.
Generally used for sulphide ores.	No such specifications are observed
Impurities are removed in form oxide gases like-$S{{O}_{2}},{{P}_{2}}{{O}_{5}}$	Moisture and other impurities are removed.
Most common example is for chalcocite ore-$2C{{u}_{2}}S+3{{O}_{2}}\to 2C{{u}_{2}}O+2S{{O}_{2}}$	Most common example is calcination of limestone-\[CaC{{O}_{3}}\xrightarrow{\Delta }CaO+C{{O}_{2}}(g)\]

These are the few differences between the two processes.

Additional Information: Calcination is carried out in a reactor or a furnace which are after referred as kilns. Calcination of limestone is a very common reaction which is used in formation of cement industrially. However, calcination is also used for removal of aluminium ions from zeolites during their synthesis.
Roasting is an exothermic process and is carried out in a reverberatory furnace. In early age, roasting was carried out by burning wood on top of ore so that its temperature would rise to a point where sulphur became its fuel i.e. no external fuel sources were required. However, this produced a large amount of toxic acidic and metallic compounds.

Note: It is important to remember that calcination is an oxygen deficient process and roasting is an oxygen excess process. It is also important to remember that calcination should not be confused with calcification which is a completely different process in biology.