Rate Law (Dependence of rate on concentration of reactants)
The representation of rate of reaction in terms of the concentration of the reactants is called the rate law. It can only be established by experiments.
Generally, rate law expressions are not simple and these may differ for the same reaction on conditions under which the reaction is being carried out.
But for large number of reactions starting with pure reactants we can obtain simple laws. For these reactions:
K = Rate constant = specific reaction rate = rate of reaction when concentration is unity
Unit of K = (conc) 1-order time-1
Value of K is constant for a given reaction, depends only on temperature.