The colour of the coordination compounds depends on the crystal field splitting . What will be the correct order of obsorption of wavelength of light in the visible region, for the comolexes, `[Co(NH_(3))_(6)]^(3+)`m and `[Co(H_(2)O)_(6)^(3+)`?

Options

A. `[Co(CN)_(6)]^(3-)gt[CO(NH_(3))_(6)]^(3+) gt[Co(H_(2)O)_(6)]^(3+)`
B. `[Co(NH_(3))_(6)]^(3+)gt[Co(H_(2)O)_(6)]^(3+)gt[Co(CN)_(6)]^(3-)`
C. `[Co(H_(2)O)_(6)]^(3+)gt[Co(NH_(3))_(6)^(3+)gt[Co(CN)_(6)]^(3-)`
D. `[Co(CN)_(6)]^(3-)gt[Co(NH_(3))_(6)]^(3+)gt[Co(H_(2)O)_(6)]^(3+)`

Explanation

(c) As we know that, strong field ligand split the five degenerate energy levers with more energy separation thean weak field ligand, i.e as strenght of ligand increaeses crystal field spilting energy increases.
Hence " " `DeltaE=(hc)/(lambda)`
`rArr" " DeltaEprop(1)/(lambda)rArrlambdaprop(1)/(DeltaE)`
As energy seperation increases, the wavelength decreases/
Thus. the correct order is
`[Co(H_(2)O)]^(3+)gt[Co(NH_(3))_(6)]^(3+)gt[Co((CN)_(6)]^(3-)`
Hence strength of ligand increaase. `DeltaE` inceases CFSE increaese and `lambda` absored decrease.