Question

Mention ‘C’ and ‘R’ for ores that can be oxidised by calcination and roasting respectively and write the chemical reactions taking place.​

Ore	C/R	Chemical reaction
Bauxite (${\text{Al}}_2{\text{O}}_3.2{\text{H}}_2\text{O}$)
Galena (PbS)​
Magnesite (${\text{MgCO}}_3$)

Answer 1

Bauxite (${\text{Al}}_2{\text{O}}_3.2{\text{H}}_2\text{O}$) is a hydrated ore and hence the calcination process needs to be applied. Chemical reaction is represented as:

${\mathrm{Al}}_2{O}_3.2H_{2}O\stackrel{\mathrm{Heat}}{\to }{\mathrm{Al}}_2{O}_3+2H_{2}O$

Galena (PbS) is a sulphide ore and hence the roasting method needs to be applied. Chemical reaction is represented as:

$2\mathrm{PbS}+3O_2\stackrel{\mathrm{Heat}}{\to }2\mathrm{PbO}+2{\mathrm{SO}}_2$

Magnesite (${\text{MgCO}}_3$) is a carbonate ore and hence the metal oxide can be produced by calcination.

${\mathrm{MgCO}}_3\stackrel{\mathrm{Heat}}{\to }\mathrm{MgO}+{\mathrm{CO}}_2$