`AIF_3` does not dissolve in anhydrous HF but dissolves in KF. When `BF_3` is added to the above solution containing KF, aluminium trifluoride is precipitated. Explain.

Explanation

`AIF_3` does not dissolve in anhydrous HF because it is not available for coordination with `AIF_3` due to the presence of intermolecular hydrogen bonding. It dissolves in KF because `F^(- )` ion can coordinate with `AIF_3` to form a salt.
`3KF + AIF_3 to K_3[AIF_6]`
The salt is decomposed by `BF_3` which is a Lewis acid (electron deficient) and `AlF_3` is precipitated.
`K_3 [AlF_6]+3BF_3 to AIF_3 darr +3KBF_4`