What determines the strength of an acid?

The strength of an acid is fundamentally determined by its ability to donate protons (H⁺ ions) to a solution, as well as the extent to which it dissociates in that solution. Strong acids fully dissociate in water, releasing a greater number of protons compared to weak acids, which only partially dissociate. This distinction is critical because the concentration of protons in a solution directly relates to the acidity of that solution.

When considering the ability of an acid to donate protons, it's important to recognize that the more fully an acid dissociates, the stronger it is. For example, hydrochloric acid (HCl) is a strong acid that completely dissociates to provide H⁺ ions in solution, while acetic acid (CH₃COOH), a weak acid, does not dissociate completely. Hence, both the inherent ability to donate protons and the extent of dissociation are key factors in determining the strength of an acid.