Acid/Base Equilibria

Ionic equilibria can be classified into two categories: homogeneous equilibria, and heterogeneous equilibria. As an acid is a molecule capable of ceding protons to another molecule and a base is a molecule capable of capturing protons from another molecule, for each acid, there is a corresponding base. Amphiprotic solvents give rise to an acid-base equilibrium between a molecule of solvent acting as an acid and a second molecule of solvent acting as a base. Acids are classified by a value called the acidity constant, which depends on the solvent in which the acid-base reactions take place. The strongest acid that can exist in a solution is the positive ion yielded by the autoprotolysis of the solvent. The strongest base which can exist in a solution is the negative ion created by the autoprotolysis of the solvent. This phenomenon is known as the leveling effect of a solvent.