Co-Ordination Compounds Question 78
Question: An aqueous solution of $ CoCl_2 $ on addition of excess of concentrated HCl turns blue due to formation of
[AIIMS 2005]
Options:
A) $ [Co{{(H_2O)}_4}Cl_2] $
B) $ {{[Co(H_2O)2Cl_4]}^{2-}} $
C) $ {{[CoCl_4]}^{2-}} $
D) $ [Co(H_2O)2Cl_2] $
Show Answer
Answer:
Correct Answer: C
Solution:
$ CoCl_2 $ is a weak Lewis acid, reacting with chloride ion to produce salt containing the tetrahedral $ {{[CoCl_4]}^{2-}} $ ion.
$ CoCl_2 $ is blue when anhydrous, and a deep magneta colour when hydrated, for this reason it is widely used as an indicator for water.
