What is a Dissociation Constant?
The dissociation constant, Ka, is a measure of how strong an acid is. The higher the dissociation constant, the stronger the acid. For example, Acetic Acid has a Ka of 0.00001754 and a pKa of 4.76 (4.76 is the negative log of 0.00001754) and is a weakly dissociated acid. As shown in the following formula, the dissociation constant is actually an equilibrium constant. The use of square brackets indicates molar concentration. For example, [Acetic Acid] is the molar concentration of Acetic Acid. As shown in the formula, when Acetic Acid is added to water, very little of it converts to hydrogen ion and acetate ion. Most of it stays in the form of undissociated Acetic Acid. A strong acid like Nitric Acid, on the other hand, is mostly converted to hydrogen ions and nitrate ions, as indicated by its large dissociation constant.
