For a weak base in aqueous equilibrium, the base dissociation constant Kb (or its logarithmic form, pKb) quantifies the extent to which the base accepts a proton from water to produce its conjugate acid and hydroxide ion, consistent with the Bronsted-Lowry definition of a base as a proton acceptor (and the Arrhenius definition as a species that raises hydroxide concentration). Using an equilibrium expression for Kb in terms of equilibrium concentrations of products and reactants (excluding solvent), the hydroxide concentration can be determined, and via the water autoionization relationship pKw = pOH + pH = 14 (at 25°C), the hydroxide concentration is converted to pOH and then to pH. This belongs to acid-base equilibrium chemistry, a subdomain of chemical equilibrium, and mirrors the analogous weak-acid/Ka framework by symmetry between conjugate acid-base behavior.
For a weak base in aqueous equilibrium, the base dissociation constant Kb (or its logarithmic form, pKb) quantifies the extent to which the base accepts a proton from water to produce its conjugate a…