What makes HCl a strong acid?

Oct 11, 2016

The protonolysis reaction lies strongly to the right.

Explanation:

As an acid, hydrochloric acid undergoes protonolysis in water as shown:

$H C l \left(a q\right) + {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} \left(a q\right) + C {l}^{-} \left(a q\right)$

This equilibrium lies strongly, almost quantitatively to the right, and it is the position of this equilibrium that justifies our designation of $H C l$ as a strong acid.

O the other hand, for the congeneric hydrogen fluoride:

$H F \left(a q\right) + {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} \left(a q\right) + {F}^{-} \left(a q\right)$,

this equilibrium lies to the LEFT HAND SIDE, and $H F$ is not considered to be a strong Bronsted acid.