Calcination vs Roasting: Complete Comparison

Side-by-Side Comparison

Parameter	Calcination	Roasting
Definition	Heating in limited/absent air	Heating in excess air
Ore type	Carbonate and hydrated ores	Sulphide ores
Atmosphere	No/limited O2	Excess O2 (air stream)
Gas released	CO2 (carbonates) or H2O (hydrated)	SO2
Type of reaction	Decomposition/thermal dissociation	Oxidation
Temperature	High (but no specific value tested)	High (excess air maintained)
Product	Metal oxide + CO2/H2O	Metal oxide + SO2

Key Reactions

Calcination examples: $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2$ $FeCO_3 \xrightarrow{\Delta} FeO + CO_2$ $Al_2O_3 \cdot 2H_2O \xrightarrow{\Delta} Al_2O_3 + 2H_2O$

Roasting examples: $2ZnS + 3O_2 \xrightarrow{\Delta} 2ZnO + 2SO_2$ $2PbS + 3O_2 \xrightarrow{\Delta} 2PbO + 2SO_2$ $4CuFeS_2 + 13O_2 \rightarrow 4CuO + 2Fe_2O_3 + 8SO_2$

NEET Trap

Both produce metal oxides — the key distinguishing factor is the atmosphere (limited vs excess air) and the ore type (carbonate/hydrated vs sulphide). A common wrong answer is applying calcination to sulphide ores.