The main difference between the order of a reaction and molecularity of a reaction are given below:
|
ORDER OF A REACTION |
MOLECULARITY OF A REACTION |
| It is sum of the concentration terms on which the rate of reaction actually depends or it is the sum of the exponents of the concentrations in the rate law equation. | It is the number of atoms, ions or molecules that must collide with one another simultaneously so as to result into a chemical reaction. |
| It need not be a whole number i.e. it can be fractional as well as zero. | It is always a whole number. |
| It can be determined experimentally only and cannot be calculated. | It can be calculated by simply adding the molecules of the slowest step. |
| It is for the overall reaction and no separate steps are written to obtain it. | The overall molecularity of a complex reaction has no significance. It is only slowest step whose molecularity has significance for the overall reaction. |
| Even the order of a simple reaction may not be equal to the number of molecules of the reactants as seen from the unbalance equation. | For simple reactions, the molecularity can usually be obtained from the Stoichiometry of the equation. |
