Which one of the following reactions does not occur during extraction of copper ?

The following changes occur during smelting.

(a) Most of the ferrous sulphide gets oxidised to ferrous oxide which combines with silica (flux) to form fusible slag.

$2\mathrm{FeS} + 3{\mathrm{O}}_2 \to 2\mathrm{FeO} + 2{\mathrm{SO}}_2$

$\mathrm{FeO} + {\mathrm{SiO}}_2 \to {\mathrm{FeSiO}}_3$ (Ferrous silicate)

The slag being lighter floats and forms the upper layer. It is removed through the slag hole from time to time.

(b) During roasting or in the blast furnace if any oxide of copper is formed, it combines with FeS and is changed back into its sulphide.

$2{\mathrm{Cu}}_2\mathrm{S} + 3{\mathrm{O}}_2 \to 2{\mathrm{Cu}}_2\mathrm{O} + 2{\mathrm{SO}}_2$

${\mathrm{Cu}}_2\mathrm{O} + \mathrm{FeS} \to {\mathrm{Cu}}_2\mathrm{S} + \mathrm{FeO}$

Ferrous oxide thus formed again combines with silica to form more slag.

$\mathrm{FeO}+{\mathrm{SiO}}_2\to {\mathrm{FeSiO}}_3$

So, no formation of calcium silicate $\left({\mathrm{CaSiO}}_3\right)$ in extraction of $\mathrm{Cu}$.