Question

Which of the following complex ions absorbs the light of minimum wavelength?

• A. $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$
• B. $\left[\text{C} \text{o} \text{F}_{6}\right]^{3 -}$
• C. $\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}$
• D. $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$

Answer 1

Answer: (C)

Wavelength of light absorb $ \propto \frac{1}{\text{s} \text{t} \text{a} \text{b} \text{i} \text{l} \text{i} \text{t} \text{y} \, \text{o} \text{f} \, \text{c} \text{o} \text{m} \text{p} \text{l} \text{e} \text{x}}$

$\text{C} \text{N}^{-}$ is strong field ligand

So complex is more stable