Why does the reaction.

proceed better with KF than with NaF ?

Explanation

The standard enthalpies of alkali metal chlorides become more and more negative on moving down the group, i.e.. `Delta_(f)H^(Θ)` of KCI is more negative than `Delta_(f)H^(Θ)` of NaCI. Therefore, the above reaction proceeds better with KF than with NaF.