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

Options

A. `[Co(CN)_(6)]^(3-) gt [Co(NH_(3))_(6)]^(3+)gt [Co(CN)_(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+)`

Answer

C

Explanation

The CFSE of the ligands are in the order
` H_(2) Olt NH_(3)lt CN^(-)`
Therefore , wavelength will be in the opposite order as
`[Co(H_(2)O)_(6)]^(3+) gt [Co(NH_(3))_(6) ]^(3+) gt [Co (CN)_(6)]^(3-)`