Question

Justify that the reaction:

2Cu₂O(s) + Cu₂S(s) → 6Cu(s) + SO₂(g) is a redox reaction. Identify the species oxidised/reduced, which acts as an oxidant and which acts as a reductant.

Answer 1

First of all, assign oxidation number to each of the species in the given reaction.

\(2\overset{+1}{Cu}_2\overset{-2}{O}(s)+\overset{+1}{Cu_2}\overset{-2}{O}(s)\rightarrow6\overset{o}{Cu}(s)+\overset{+4}{S}\,\overset{-2}{O}(g)\)

So, it is concluded that in this reaction, copper is reduced from +1 oxidation state to zero oxidation state and Sulphur is oxidised from -2 oxidation state to +4 oxidation state.

Hence, this reaction is a redox reaction.

Further, Cu₂O is used to oxidise Sulphur. So, Cu(l) is an oxidant and Sulphur of CuS is used to reduce copper both in CuS itself and Cu₂O to decrease its oxidation number, so, Sulphur of Cu₂S is a reductant.