Question

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

• A. $\left[ Co \left( H _{2} O \right)_{6}\right]^{2+}$ is transformed into $\left[ CoCl _{6}\right]^{4-}$
• B. $\left[ Co \left( H _{2} O \right)_{6}\right]^{2+}$ is transformed into $\left[ CoCl _{4}\right]^{2-}$
• C. tetrahedral complexes have smaller crystal field splitting than octahedral complexes
• D. both (2) and (3)

Answer 1

Answer: (D)

Deep blue intense colour present in tetrahedral chloro complex.
i.e. $\left[ CoCl _{4}\right]^{2-}$