Rate Law

Over a period of time, rate of the reaction slowly decreases as the reactants are consumed. Rate is directly proportional to the concentration of the reactants raised to some power.

xA (g) + yB (g) → Products

Rate ∝ [A]^x[B]^y

Rate = k[A]^x[B]^y

where k is the constant of proportionality.

Rate law is defined as the mathematical relationship between rate of a reaction and the concentration of the reactants.  The constant k in the rate law is called the rate constant. It is numerically equal to the rate of the reaction if all the concentrations were set equal to unity.

Each reaction is characterized by its own rate constant, whose value is dependent on the temperature, but independent of concentration of the reactants.