Consider the reactions :
(a) `H_(3)PO_(2) (aq) + 4 AgNO_(3) (aq) + 2 H_(2)O (1) to H_(3) PO_(4) ( aq) + 4 Ag(s) + 4HNO_(3)(aq)`
(b) `H_(3)PO_(2) (aq) + 2Cu SO_(4)(aq) + 2H_(2)O(1) to H_(3) PO_(4)(aq) + 2 Cu(s) + H_(2)SO_(4)(aq)`
(c) `C_(6)H_(5) CHO(1) + 2[Ag (NH_(3))_(2)]^(+) (aq) + 3 OH^(-) (aq) to C_(6)H_(5)COO^(-)(aq) + 2Ag(s) + 4NH_(3)(aq) + 2 H_(2)O(1)`
(d) `C_(6)H_(5)CHO(1) + 2Cu^(2+) (aq) + 5 OH^(-) (aq) to ` No change observed .
What inference do you draw about the behaviour of `Ag^(+)` and `Cu^(2+)` from these reactions ?

Explanation

Reactions `(a)` and `(b)` indicate that `H_(3)PO_(2)` (hypophosphorus acid) is a reducing agent and thus reduces both `AgNO_(3)` and `CuSO_(4)` to `Ag` and `Cu`, respectively. Conversely, both `AgNO_(3)` and `CuSO_(4)` act oxidising agent and thus oxidise `H_(3)PO_(2)` to `H_(3)PO_(3)` (phosphorus acid).
Reaction `(c )` suggests that `[Ag(NH_(3))_(2)]^(+)` oxidises `C_(6)H_(5)CHO` (benzaldehyde) to `C_(6)H_(5)COO^(Θ)` (benzotate ion), but reaction (d) indicates that `Cu^(2+)` ions cannot oxidise `C_(6)H_(5)CHO` to `C_(6)H_(5)COO^(Θ)`. Therefore, from the above reactions, we conclude that `Ag^(o+)` ion is a stronger oxidising agent than `Cu^(2+)` ion.