Question

How is fluorine isolated from flurides using Dennis method.

Answer 1

In Dennis method, pure, dry and anhydrous potassium hydrogen fluoride $\left(KH{F}_2\right)$ is electrolyzed in the molten state at $523K$ when hydrogen is liberated at the cathode while $F_2$ is liberated at anode.

$KH{F}_2⟶KF+HF$

$KF⟶K^{+}+F^{-}$

At anode:-

$F^{-}⟶\frac{1}{2}{F}_2+e^{-}$

At cathode:-

$K^{+}+e^{-}⟶K$

$K+HF⟶KF+\frac{1}{2}{H}_2$