What is the law of mass action?

The law of mass action basically means that the rate at
which a reaction takes place depends on the concentration of the reactants in the
reaction.

Thus, if you have a general reaction of the
form:

A + B --> C

then
the rate of the reaction, k, = [A][B] where the brackets indicate molar
concentrations.

What this means is that if you increase the
concentration of one or more of the reactants you can increase the rate at which the
reactants combine to form the desired product.