NH3 + H2O NH4+ + OH–
As in the case of acetic acid, the current conducted by 0.001 M NH3 (Table 1 from Ions in Solution) is slightly above 10 percent that of 0.001 M NaOH or KOH, indicating that somewhat more than one-tenth of the NH3 molecules have been converted to NH4+ and OH– ions.
Weak bases fall into two main categories.
(CH3)3N + H2O (CH3)3NH+ + OH–
Anions of weak acids The fact that the molecules of a weak acid are not entirely converted into hydronium ions and anions implies that those anions must have considerable affinity for protons. For example, the anion of acetic acid, acetate ion, can accept protons as follows:
C2H3O2– + H2O HC2H3O2 + OH–
Thus when a compound like sodium acetate,dissolves, some hydroxide ions are produced and the solution becomes slightly basic. (Sodium ions do not react with water at all, and so they have no effect on acidity or basicity.) Other examples of weak bases which are anions of weak acids are CN–, CO32–, PO43–.