Skip to Content
Medical Term:

equilibrium constant


Definition: in the reaction A + B ? C + D at equilibrium (no net change in concentrations of A, B, C, or D), the concentrations of the four components are related by the equation Keq = [C][D]/[A][B]; Keq is the equilibrium constant If any component in the reaction has a multiplier (H2 ? 2H), that multiplier appears as an exponent in the calculation of K (Keq = [H]2/[H2]). When this equation is applied to the ionization of a substance in solution, Keq is called the dissociation constant (Kd) and its negative logarithm (base 10) is the pKd.

See Also: Henderson-Hasselbalch equation, mass:action ratio

© Copyright 2016 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.