A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis reactions, and the auto-ionization of water reaction. The summative equations are weak acid negative weak base reactions. The acid ionization constants (K[subscript a]) of HC[subscript 2]H[subscript 3]O[subscript 2], H[subscript 3]PO[subscript 4], H[subscript 2] PO[subscript 4][superscript -], HPO[subscript 4][superscript 2-], and NH[subscript 4][superscript +] are determined from measurements of the pH in buffer solutions with known weak acid and known weak base concentrations, and base hydrolysis constants (K[subscript b]) are determined using K[subscript a] times K[subscript b ]= K[subscript w].