Acid dissociation constant

Measure of an acid's strength in solution

In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ⁠ K a {\displaystyle K_{a}} ⁠) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction HA ↽ − − ⇀ A − + H + {\displaystyle {\ce {HA <=> A^- + H^+}}} known as dissociation in the context of acid–base reactions. The chemical species HA is an acid that dissociates into A−, called the conjugate base of the acid, and a hydrogen ion, H+.

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