Consider the reactions:

(a) H₃PO₂(aq) + 4 AgNO₃(aq) + 2 H₂O(l) → H₃PO₄(aq) + 4Ag(s) + 4HNO₃(aq)

(b) H₃PO₂(aq) + 2CuSO₄(aq) + 2 H₂O(l) → H₃PO₄(aq) + 2Cu(s) + H₂SO₄(aq)

(c) C₆H₅CHO(l) + 2[Ag (NH₃)₂]+(aq) + 3OH^– (aq) → C₆H₅COO^–(aq) + 2Ag(s) +4NH₃ (aq) + 2 H₂O(l)

(d) C₆H₅CHO(l) + 2Cu²⁺(aq) + 5OH^–(aq) → No change observed.

What inference do you draw about the behaviour of Ag⁺and Cu²⁺from these reactions?

In the above given reactions we can clearly see that:

(a) H₃PO₂(aq) + 4 AgNO₃(aq) + 2 H₂O(l) → H₃PO₄(aq) + 4Ag(s) + 4HNO₃(aq)
Inference: Ag is getting reduced and P is getting oxidised.

(b) H₃PO₂(aq) + 2CuSO₄(aq) + 2 H₂O(l) → H₃PO₄(aq) + 2Cu(s) + H₂SO₄(aq)

Inference: Cu is getting reduced and P is oxidised.

(c) C₆H₅CHO(l) + 2[Ag (NH₃)₂]+(aq) + 3OH^– (aq) → C₆H₅COO^–(aq) + 2Ag(s) +4NH₃ (aq) + 2 H₂O(l)

Inference: Ag is getting reduced and C₆H₅CHO is getting oxidised.

(d) C₆H₅CHO(l) + 2Cu²⁺(aq) + 5OH^–(aq) → No change observed.

Inference: No reaction as Cu cannot oxidize C₆H₅CHO.

Hence, as a whole Ag⁺ and Cu²⁺ act as oxidising agents in reactions (a) and (b) respectively. In reaction (c), Ag⁺ oxidises C₆H₅CHO to  C₆H₅COO^- , but in reaction (d), Cu²⁺ cannot oxidise C₆H₅CHO . Hence, we can say that Ag⁺ is a stronger oxidising agent than Cu²⁺.