Question

Partial roasting of sulphide ores is done in the metallurgical operation of copper. Why?

Answer 1

• Roasting is the process of heating sulfide ores to a high temperature in the presence of air.
• The concentrated ore is heated in excess supply of oxygen copper pyrites( ${\mathrm{CuFeS}}_2$).
• The copper sulfide becomes copper oxide which again reacts with unreacted carbon sulfide and gives auto-reduction.

$2\mathrm{CuS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{CuO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right)$

$2\mathrm{CuO}\left(\mathrm{s}\right)+\mathrm{CuS}\left(\mathrm{s}\right)\stackrel{\mathrm{Auto}-\mathrm{reduction}}{\to }3\mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)$