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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. |
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Answer» Solution :Aqueous `CuSO_(4)` solution exists as `[Cu(H_(2)O)_(4)]SO_(4)` which has blue COLOUR due to `[Cu(H_(2)O)_(4)]^(2+)` ions. (i) When KF is added, the weak `H_(2)O` LIGANDS are replaced by `F^(-)` ligands FORMING `[CuF_(4)]^(2-)` ions which is a green precipitate. `[Cu(H_(2)O)_(4)]^(2+)+4F^(-)rarrunderset(("Green ppt."))underset("Tetrafluorocuprate(II)")([CuF_(4)]^(2-))+4H_(2)O` (ii) When KCl is added, `Cl^(-)` ligands replace the weak `H_(2)O` ligands forming `[CuCl_(4)]^(2-)` ION which has bright green colour. `[Cu(H_(2)O)_(4)]^(2+)+4Cl^(-)rarrunderset(("Green solution"))underset("Tetrachlorocuprate(II)")([CuCl_(4)]^(2-))+4H_(2)O` Alternatively, directly we can write the REACTION as : `CuSO_(4)(aq)+4KF(aq)rarrK_(2)[CuF_(4)]+K_(2)SO_(4)` `CuSO_(4)(aq)+4KCl(aq)rarrK_(2)[CuCl_(4)]+K_(2)SO_(4)` |
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