The base ionization constant, Kb, for the acetate ion (C2H3O2–) is a measure of the strength of this ion as a base in water. The acetate ion can accept a proton (H+) from water, resulting in the formation of acetic acid (C2H4O2) and hydroxide ions (OH–). The equilibrium reaction is:
C2H3O2– + H2O ⇌ C2H4O2 + OH–
The Kb value for the acetate ion is approximately 5.6 x 10-10. This value indicates that the acetate ion is a weak base, as it only partially ionizes in solution. The small value of Kb reflects the fact that the equilibrium strongly favors the reactants, meaning that acetate does not significantly increase the concentration of hydroxide ions in solution.