Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF_(3) is bubbled through. Give reasons.

Aluminium trifluoride is insoluble in anhydrous HF but dissolves on ad

1.	Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF_(3) is bubbled through. Give reasons.
Answer» Solution :AlF3 does not dissolve in anhydrous HF because HF is a covalent compound and is strongly HYDROGEN bonded. NaF is an ionic compound and provides `F^-` IONS which combine with `AlF_3` to form a soluble complex, `Na_3 [AlF_6]`. Therefore, `AlF_3` DISSOLVES in presence of NaF. `3NaF + AlF_3 to underset("Sodium hexafluoroaluminate (III)")(Na_3 [ AlF_6])` When gaseous `BF_3` is bubbled through the RESULTING solution, boron because of its smaller size and higher electronegativity, enters into the complex and expels aluminium. Thus, `AlF_3`gets precipitated. `Na_3 [AlF_6] + 3BF_3 to underset("Sod. TETRAFLUOROBORATE (III) (soluble)")(3Na[BF_4]) + underset("insoluble")(AlF_3) darr`