Question

[fe(CN)6]^-4and [Fe(h2o)6]^2 are of different. colours in dilute solutions .why,?​

Answer 1

$[Fe(CN)_6]^{4-}$ is an inner orbital octahedral complex since CN⁻ is a strong field ligan d and causes the electrons to pair up.

On the other hand, in $[Fe(H_2O)_6]^{2+}$, water is a weak field ligan d

This means, CN⁻ has a higher crystal field splitting energy value than water.

Hence absorption energy of  d-d transition also differs. So there is difference in their colors.

HOPE THIS HELPS!!