Where K is the equilibrium constant, A,B,C,D are the equilibrium concentrations of aqueous/gaseous compounds, a,b,c,d are the coefficients in the balanced chemical equation.
The equilibrium constant is related to the rate constants of the forward and reverse reactions. It is always the same for a given reaction at a given temperature. Since k changes with temp, so does K.
Any reaction that contains compounds in two different states is referred to as heterogeneous. Liquid and solid compounds are not involved in the equilibrium law. They are actually incorporated into K because they do not change. The concentration of a liquid or a solid is their densities; regardless of how much solid or liquid is present. This is not true for aqueous and gaseous compounds, where the concentration changes depending on the volume of the container.
Magnitude of K:
K represents the relative position of the equilibrium.
If K is large (K>1), this means the numerator is larger than the denominator and the products are more concentrated than the reactants. The equilibrium is more to the right.
If K is small (K<1), this means the numerator is smaller than the denominator and the reactants are more concentrated than the products. The equilibrium is more to the left.
If the equilibrium concentrations are [I2]=[H2]=0.442M, [HI]=3.116M