Justify that the reaction : `2Cu_(2) O(s) + Cu_(2)S (s) rarr 6 Cu (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 :
`2 overset(+1)(Cu_(2))overset(-2)(O(s)) + overset(+1)(Cu_(2))overset(-2)(S(s)) rarr 6 overset(0)(Cu(s)) + overset(+4-2)(SO_(2))`
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.