What makes #HCl# a strong acid?

1 Answer
Oct 11, 2016

The protonolysis reaction lies strongly to the right.


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

#HCl(aq) + H_2O(l) rightleftharpoons H_3O^+(aq) + Cl^(-)(aq)#

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

O the other hand, for the congeneric hydrogen fluoride:

#HF(aq) + H_2O(l) rightleftharpoons H_3O^+(aq) + F^(-)(aq)#,

this equilibrium lies to the LEFT HAND SIDE, and #HF# is not considered to be a strong Bronsted acid.