When concentrated HCl is added to aqueous solution of C o C l 2 , its colour changes from reddish pink to…

When concentrated HCl is added to aqueous solution of CoCl2, its colour changes from reddish pink to deep blue. Which complex ion gives blue colour in reaction?
  1. CoCl64-
  2. CoCl63-
  3. CoH2O62+
  4. CoCl42-

Solution

On addition of conc. HCl. The equilibrium between two coloured Co (II) species can be described by equation

CoH2O6aq2++4Claq-⇌CoCl4aq2-+6H2OℓPinkBlue

The equilibrium is disturbed by changing the conc. of Cl- ions by addition of conc. HCl in forward direction.
 
     
 

Asked in: JEE Main 2015 (11 Apr Online)

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