(i) Which is a stronger reducing agent `Cr^(2+)` or `Fe^(2+)` and why ?
(ii) Explain why `Cu^(+)` ion is not stable in aqueous solution ?
(iii) Explain why `Ce^(4+)` is a stronger oxidizing agent.

Explanation

(i) `Cr^(2+)` is a stronger reducing agent than `Fe^(2+)` because `Cr^(2+) rarr Cr^(3+) + e^(-)` results in change of configuration from `d^(4)` to more stable `d^(3) ( t_(2g)^(3))` than from `d^(6)` to `d^(5)` in case of the change `Fe^(2+) rarr Fe^(3+) + e^(-)` .
(ii) This is because `Cu^(+)` ion in aqueous solution undergoes disproportionation to give more stable `Cu^(2+)` and Cu.
(iii) This is because`Ce^(4+)` tends to change to `Ce^(3+)` as `+3` oxidation state is more stable.