Aqueous copper sulphate solution (blue) gives - (2) a bright green solution with aqueous potassium chloride. Explain these experimental results.

Explanation

Aqueous copper sulphate contains coordination entity `[Cu(H_(2)O)_(4)]^(2+)`, which is blue in colour.
(2) On addition of aqueous KCl solution, `H_(2)O` ligands are replaced by `Cl^(-)` ligands forming the soluble complex ion `[CuCl_(4)]^(2-)`, which has a bright green colour.
`[Cu(H_(2)O)_(4)]^(2+)+underset("tetrachlorocuprate (II) ion (green)")(4Cl^(-)rarr[CuCl_(4)]^(2-)+4H_(2)O)`