Justify that the reaction :
`2Cu_(2)O_((s))+Cu_(2)S_((s))to6Cu_((s))+SO_(2(g))` is a redox reaction. Identify the species oxidised/reduced, which acts as an oxidant and which acts as a reductant.

Explanation

Let us assign oxidation number to each of the species in the reaction under examination. This results into :
`overset(+1,-2)(2Cu_(2)O_((s)))+overset(+1,-2)(Cu_(2)S_((s)))tooverset(0)(6Cu_((s)))+overset(+4,-2)(SO_(2)(g))`
We therefore, conclude that in this reaction copper is reduced from +1 state to zero oxidation state and sulphur is oxidised from -2 state to +4 state. The above reaction is thus a redox reaction.
Further, `Cu_(2)O` helps sulphur in `Cu_(2)S` to increase its oxidation number, therefore, Cu(I) is an oxidant, and sulphur of `Cu_(2)S` helps copper both in `Cu_(2)S` itself and `Cu_(2)O` to decrease its oxidation number, therefore, sulphur of `Cu_(2)S` is reductant.