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 :
+1-2 +1-2 0 +4-2
`2Cu_(2)O(S)to Cu_(2)S(s) to 6Cu(s)+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.