Question

An aqueous solution of $CoCl_2$ on addition of excess of concentrated $HCl$ turns blue due to formation of

• A. $[Co(H_2 O)_4 Cl_2 ]$
• B. $[Co(H_2 O)_2 Cl_4 ]^{2-}$
• C. $[CoCl_4 ]^{2-}$
• D. $[Co(H_2 O)_2 Cl_2 ]$

Answer 1

Answer: (C)

$[CoCl_4 ]^{2-}$

Answer 2

$CoCl _{2}$ is weak Lewis. It reacts with chloride ion to produce salt containing the tetrahedral $\left[ CoCl _{4}\right]^{2-}$ ion which is blue in colour. The oxidation state of $CO$ is $+2$.