Ncert Exercises & Solutions

An aqueous pink solution of cobalt(II) chloride changes to deep blue on addition of excess of HCl. This is because ........

1.	${[Co (H_{2} O_{6})]}^{2 +}$ is transformed into ${[{CoCl}_{6}]}^{4 -}$
2.	${[Co (H_{2} O_{6})]}^{2 +}$ is transformed into $CoCl^{2-}_4$
3.	Tetrahedral complexes have smaller crystal field splitting than octahedral complexes.
4.	Tetrahedral complexes have larger crystal field splitting than octahedral complex

Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, c)

Aqueous pink solution of cobalt (II) chloride is due to the electronic transition of electron fom

t_{2 g} to e_{g}

, the energy level of

{[Co (H_{2} O_{6})]}^{2 +}

complex. When an excess of HCI is added to this solution

(i) ${[Co (H_{2} O_{6})]}^{2 +}$ is transformed into ${[C o C l_{4}]}^{2 -}$

(ii) Tetrahedral complexes have smaller crystal field splitting than octahedral complexes because $∆_{t} = \frac{4}{9} ∆_{0}$

Hence, options (b) and (c) are correct choices.