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

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Solution

The transition of electrons from $t_{2g}$ to $e_g$ energy level gives pink colour to the aqueous solution of cobalt (II) chloride $[Co(H_2O)_6]^{2+}$ complex, when excess $HCl$ is added to the solution it forms $[CoCl_4]^{2-}$, which is blue in colour.

$[Co(H_2O)_6]^{2+}+HCl\rightarrow [CoCl_4]^{2-}$
pink Excess Blue

Hence, $[Co(H_2O)_6]^{2+}$ is transformed into $[CoCl_4]^{2-}$, it is correct option.

Crystal field splitting energy of tetrahedral complex,

$\Delta_t=\dfrac{4}{9}\Delta_0$
Where, $\Delta_0$ Crystal filed spilitting energy of octahedral complex

$\because \Delta_t<\Delta_0$

Tetrahedral complexes have a smaller crystal field splitting than octahedral complexes,
it is correct.
Hence, the correct options are (b) $\&$ (c).

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Similar questions

An aqueous pink solution of cobalt(II) chloride to deep blue on addition of excess of HCL. This is because ..........
(a) $[C o (H_{2} O)_{6}]^{2 +}$ is transformed into $[C o C l_{6}]^{4 -}$
(b) $[C o (H_{2} O)_{6}]^{2 +}$ is transformed into $[C o C l_{4}]^{2 -}$
(c) tetrahedral complexes have smaller crystal field splitting than octahedral complexes
(d) tetrahedral complexes have larger crystal field splitting than octahedral complex.

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

Q. An aqueous solution of

C o C l_{2}

on addition of excess of concentrated HCl turns blue due to formations of :

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H C l

is added to an aqueous solution of

C o {C l}_{2}

its colour changes from reddish pink to deep blue. Which complex ion gives blue colour in this reaction?

Q. Aqueous

C u S O_{4}

changes its colour from sky blue to deep blue on the addition of

N H_{3}

because:

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