Question

Is `HF` a strong acid in water?

Answer 1

`H-F` is not a strong Bronsted acid:

`HF(aq) + H_2O rightleftharpoons H_3O^+ + F^-` `;pK_a=3.17`

Explanation:

Two factors explain the reduced acidity of `HF` in relation to the lower hydrogen halides: (i) the `H-F` bond is strong; and (ii) the resultant `F^-` is small and strongly polarizing.

Both enthalpy and entropy conspire to reduce the acidity of `H-F`. The entropy effect is probably the most significant.

It is a fact that solutions of `NaF(aq)` are slightly basic. How is this consistent with the former?