There are a large number of different types of equilibrium constant which are distinguished by the specific form of equilibrium to which the constant applies and the approximations to activity made in the use of the constant. These types are indicated by a subscript following the general symbol for an equilibrium constant K, and a list is given in the following section in which many of them are introduced. Equilibrium constants have nominal units, although these are unfortunately left to be understood, which depend upon their form as well as upon any incorporation of constants into the reported value. The numeric value of a constant, and the units given to it, must be consistent.
Equilibrium constants have values which depend upon the conditions under which they are measured.
The values of equilibrium constants given here are all at 25oC and one bar pressure, either in the gas phase or in aqueous solution, unless otherwise specified. The remainder of this section is still under construction.