Question

How does `HCl` act as a strong acid?

Answer 1

Its ionization in aqueous solution is reasonably complete.....

Explanation:

And thus for `HCl(aq)`, the following equilibrium......

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

Lies almost entirely to the right........

...and `K_a=([H_3O^+][Cl^-])/([HCl(aq)])` IS NUMERICALLY LARGE.