A large number of molecules act as weak bases, forming some amount of OH^- ions when added to water. There are two common forms of weak bases

1. Molecules that can remove a proton from water, such as NH₃: NH₃ + H₂O < = > NH₄⁺ + OH^-
2. Anions derived from weak acids, such as the acetate ion, CH₃COO^-. CH₃COO^- + H₂O < = > CH₃COOH + OH^-

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