Which complex of the following pairs has the larger value of `Delta_(0)`
(i) `[Co(CN)_(6)]^(3-)` and `[Co(NH_(3))_(6)]^(3+)`
(ii) `[Co(NH_(3))_(6)]^(3+)` and `[CoF_(6)]^(3-)`
(iii) `[Co(H_(2)O)_(6)]^(2+)` and `[Co(H_(2)O)_(6)]^(3+)` .

Explanation

`[Co(CN)_(6)]^(3-)` has larger value of `Delta_(0)` than `[Co(NH_(3))_(6)]^(3+)` since `CN^(Θ)` has greater field strength than `NH_(3)` (ii) `NH_(3)` has greater field strength than `F^(Θ)` ion hence `Delta_(0)` will be greater for `[Co(NH_(3))_(6)]^(3+)`
(iii) Charge on Co in `[Co(H_(2)O)_(6)]^(2+)` is + 2 whereas charge on Co in `[Co(H_(2)O)_(6)]^(3+)` is + 3 Since charge on `Co(NH_(3))_(6)]^(3+)` is higher than `[Co(NH_(3))_(6)]^(2+) ,Delta_(0)` for `[Co(NH_3)_(6)]^(3+)` is larger than `[CoNH_(3)_(6)]^(2+)` .