$\mathrm{AlF}_{3}$ is soluble in HF only in presence of KF. It is due to the formation of\

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Professor PC Thomas Classes · Answer

(b) : $\mathrm{AlF}_{3}$ is insoluble in anhydrous HF because the $\mathrm{F}^{-}$ ions are not available in hydrogen bonded HF molecules but, it becomes soluble in presence of little amount of KF due to formation of complex, $\mathrm{K}_{3}\left[\mathrm{AlF}_{6}ight]$.\ $\mathrm{AlF}_{3}+3 \mathrm{KF} ightarrow \mathrm{K}_{3}\left[\mathrm{AlF}_{6}ight]$