Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF.Aluminium trifluoride precipitates out of theresultingsolution when gaseousBF_(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 theresultingsolution when gaseousBF_(3) is bubbled through. Give reasons.
Answer» SOLUTION :(i) Anhydrous `HF` is a covalent compoundand is strongly `H`-bonded. Therefore , it does not give `F^(-)` ions and hence `AlF_(3)` does notdissolve in `HF`. In contrast,`NAF`beingan ionic compound contains `F^(-)`ions andhence combineswith `AlF_(3)`to FORM the soluble complex. `3NaF + AlF_(3) rarr UNDERSET((" soluble complex "))underset(" Sod. hetrafluoroborate (III) ")(3Na [BF_(4)]) + AlF_(3) (s)` (ii) Because of smaller size and higher electronegativity, has high MUCH higher tendency to form complexes than Al, therefore when `BF_(3)` is added to the above solution. `AlF_(3)` gets precipitated.