Dissociation of acids

Let’s look at the dissociation of a common acid – hydrochloric acid or HCl. When HCl molecules dissolve they dissociate into H⁺ ions and Cl^- ions.

HCl is a strong acid because it dissociates almost completely.

By contrast, a weak acid like acetic acid (CH₃COOH) does not dissociate well in water – many H⁺ ions remain bound-up within the molecule.

Acids are sometimes referred to as H⁺ ion donors because they release H⁺ ions in solution for other molecules to bind to.