Question

Although there are several ores, 80% of the world copper production comes from the ore chalcopyrite ($CuFe{S}_2$). The extraction of copper from chalcopyrite involves partial roasting, removal of iron and self-reduction. In the self-reduction step, the reducing species is:

• A. $S$
• B. $O^{2-}$
• C. $S^{2-}$
• D. $S{O}_2$

Answer 1

The correct option is C $S^{2-}$

What happens during the self-reduction step?
$C{u}_{2}S+2C{u}_{2}O⟶6Cu+S{O}_2\left(g\right)$

There is a reason why the copper is called 'blister copper'.

Clearly, the metal gets reduced from (+1) oxidation state to 0 (elemental metallic copper).

However, there is no change in the oxidation state of oxygen atoms at all. That leaves us with the sulphide ion
$S^{2-}$ as the reducing species!