What does the acid dissociation constant (Ka) measure?

The acid dissociation constant (Ka) measures the strength of an acid in solution. It quantifies the extent to which an acid donates protons (H⁺ ions) to the surrounding solution when it is dissolved in water. A higher Ka value indicates that the acid more readily dissociates, thereby demonstrating a stronger acidic behavior.

This constant is specific to a particular acid and is influenced by factors such as temperature and the nature of the solvent. The value of Ka is derived from the equilibrium expression of the dissociation reaction of the acid, representing the ratio of the concentrations of the products to the concentration of the reactants at equilibrium. Therefore, determining the Ka of an acid allows us to compare the relative strengths of different acids, confirming why it is directly related to the strength of an acid in solution.