ABSTRACT
The dissociation of an acid HA can be represented as a proton transfer reaction involving a Brønsted acid:
HA H O(aq) 2+ H O A3 (aq) (aq) + <+
with the equilibrium constant1 defined by
K = a a
£
¤² ¥
¦´ . . . [1]
We saw earlier that the relative activity2 of the solvent water is given by its mole fraction, which, for most solutions, is close to unity; therefore we usually set aH O2 = 1, so that Eqn [1] becomes
Ka = a a
. . . [2]
where Ka is called the acid dissociation constant. Values of the dissociation constants for several acids and bases are listed in Table 1.
