What is the Difference Between Order of Reaction and Molecularity?

The main differences between the order of reaction and molecularity are:

1. Definition: The order of a reaction is the sum of the coefficients of the reacting species involved in the rate equation, while molecularity is the number of reacting species involved in simultaneous collisions in an elementary or simplest reaction.
2. Determination: The order of a reaction is determined experimentally, whereas molecularity is a theoretical concept derived from the reaction mechanism.
3. Nature: The order of a reaction can be zero, positive, negative, whole, or fractional, while molecularity is always a whole number.
4. Applicability: The reaction order is applicable to all chemical reactions, while molecularity is only applicable to simple reactions.
5. Relationship with Concentration: The order of a reaction describes the relationship between the concentration of a reactant and the rate of the reaction, while molecularity describes the number of molecules or ions that participate in an elementary reaction.

In summary, the order of a reaction is an experimentally determined property that relates the concentration of reactants to the rate of the reaction, while molecularity is a theoretical concept that describes the number of reacting species involved in simultaneous collisions in an elementary reaction.

Comparative Table: Order of Reaction vs Molecularity

The following table highlights the differences between the order of reaction and molecularity:

In summary, the order of reaction is an experimentally determined quantity from the rate law of the reaction, while molecularity is a theoretical concept derived from the mechanism of a reaction. The order of a reaction can be applied to all chemical reactions, including complex reactions, whereas molecularity is only applicable to simple, elementary reactions.