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