Chemical Balance (continued)

Equilibrium Constant (Kc)

Observe the following chemical reaction. Being direct reaction 1 and inverse reaction 2.

According to the kinetic law or law of speed:

At the moment of equilibrium:

Isolating K:

The division of two constants in mathematics gives rise to a third constant:

KC = equilibrium constant as a function of concentrations


Knowing the value of the concentrations of the substances at equilibrium, the constant KC can be calculated. The equilibrium constant has no unity, it is dimensionless.

The equilibrium constant KC is given by the ratio (division) of product concentrations by the concentration of direct reaction reagents, raised to exponents equal to their stoichiometric chemical reaction coefficients.

This formula represents the Law of Mass Action Or the Guldberg-Waage Law.