Question

Is `HCl` a strong acid or strong base? How is the determined?

Answer 1

`"Hydrogen chloride"` is a `"strong acid"`.

Explanation:

Acidity (and we usually specify an aqueous solvent) is assessed on the basis of the completeness of the following equilibrium:

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

Hydrogen chloride is acidic because it increases the concentration of the characteristic cation of the solvent, i.e. `H_3O^+`, `"the hydronium ion"`.

On the other hand, hydrogen fluoride is a weak acid, because the equivalent equilibrium lies farther to the left:

`HF(l) + H_2O(l) rightleftharpoons H_3O^(+) + F^-`

Fluoride is a stronger base than chloride, and hence hydrogen fluoride is a weak acid.