The pyrometallurgical process of extraction is suitable for converting

a. Bauxite into aluminium.

b. Zinc oxide into zinc.

c. Hematite into iron.

Free energy of formation, $∆{\mathrm{G}}_{\mathrm{f}}$ of $\mathrm{MgO}\left(\mathrm{s}\right)$ and $\mathrm{CO}\left(\mathrm{g}\right)$ at $1273 \mathrm{K}$ and $2273 \mathrm{K}$ are given below.

${\mathrm{\Delta G}}_{\mathrm{f}}\left[\mathrm{MgO}\left(\mathrm{s}\right)\right]=-941 \mathrm{kJ} {\mathrm{mol}}^{-1} \text{at} 1273 \mathrm{K}$

${\mathrm{\Delta G}}_{\mathrm{f}}\left[\mathrm{MgO}\left(\mathrm{s}\right)\right]=-341 \mathrm{kJ} {\mathrm{mol}}^{-1} \text{at} 2273 \mathrm{K}$

${\mathrm{\Delta G}}_{\mathrm{f}}\left[\mathrm{CO}\left(\mathrm{g}\right)\right]=-439 \mathrm{kJ} {\mathrm{mol}}^{-1} \text{at} 1273 \mathrm{K}$

${\mathrm{\Delta G}}_{\mathrm{f}}\left[\mathrm{CO}\left(\mathrm{g}\right)\right]=-628 \mathrm{kJ} {\mathrm{mol}}^{-1} \text{at} 2273 \mathrm{K}$

The temperature at which carbon can be used as a reducing agent for $\mathrm{MgO}\left(\mathrm{s}\right)$ is

${\mathrm{CuFeS}}_2+{\mathrm{O}}_2\to \left(\mathrm{A}\right)+\left(\mathrm{B}\right)+{\mathrm{SO}}_2$

$\left(\mathrm{B}\right)+{\mathrm{O}}_2\to \left(\mathrm{C}\right)+{\mathrm{SO}}_2$

$\left(\mathrm{C}\right)+{\mathrm{SiO}}_2\to \left(\mathrm{D}\right)$

Main source of lead is $\mathrm{PbS}$. It is converted to $\mathrm{Pb}$ by:

Self-reduction process is: