Equilibrium Law

In an equilibrium system at a given temperature, there is a constant ratio (K) between the concentration of products and the concentration of reactants. Note, however, that this value will vary with temperature.

For an equilibrium system of the general form...

The equilbrium constant is given by...

Substances in the solid or liquid phase are excluded from the equilibrium constant equation.

For example, the system given by...

Would have the equilibrium constant...

K can be used to qualitatively predict the relative amounts of products and reactants present at equilibrium.

For example, if K is large (greater than 1), then there is a large amount of products relative to reactants at equilibrium. Likewise, if K is small (less than 1), then there is a large amount of reactants relative to products at equilibrium.