CBSE · Class 10 · Science · Metals and Non-metalsDifferentiate between Roasting and Calcination with suitable chemical equations. In which step of metallurgy are these processes used?

Roasting and calcination are pyrometallurgical operations used to convert concentrated ores into metal oxides during the extraction of moderately reactive metals.

1. Roasting:

• It is the process of heating a concentrated ore strongly in the presence of excess air below its melting point.
• It is used for sulfide ores to convert them into metal oxides.
• Equation: $$2ZnS(s) + 3O_2(g) \xrightarrow{\Delta} 2ZnO(s) + 2SO_2(g)$$

2. Calcination:

• It is the process of heating a concentrated ore strongly in the limited supply or absence of air below its melting point.
• It is used for carbonate or hydrated ores to remove moisture and carbon dioxide.
• Equation: $$ZnCO_3(s) \xrightarrow{\Delta} ZnO(s) + CO_2(g)$$

Both methods are performed during the conversion of concentrated ore into metal oxide, which is subsequently reduced to free metal.