Aqueous copper sulphate solution (blue in colour) gives: (i) a green precipitate with aqueous potassium fluoride and (ii) a bright green solution with aqueous potassium chloride. Explain these experimental results.

Explanation

Aqueous `CuSO_4` solution exists as `[Cu(H_2O)_4]SO_4` which has blue colour due to `[Cu(H_2O)_4]^(2+)` ions.
(i). When KF is added, the weak `H_2O` ligands are replaced by `F^(ɵ)` ligands forming `[CuF_4]^(2-)` ions which is a green precipitate.
`[Cu(H_2O)_4]^(2+)+4F^(ɵ)underset("Tetrafluorocuperate"(II))([CuCl]^(2-))+4H_2O`
The reaction can also be written as such
`CuSO_(4(aq))+4KF_(aq)toK_2[CuF_4]+K_2SO_4`
`CuSO_(4(aq))+4KCl_(aq)toK_2[CuCl_4]+K_2SO_4`