Molecularity and Order

[nicole_ershaghi 3F]

Are molecularity and order related in any way?

[106036120]

Molecularity is the amount of molecules involved in a collision. This is just how many reactants there are in an elementary reaction. Order is the sum of the powers of all the reactants in the rate law. This can be determined experimentally.

[Sophia Lim 2A]

While molecularity and order both describe aspects of chemical reactions, they are not directly related in a one-to-one manner. However, for elementary reactions, there can be a relationship between molecularity and order:

- For elementary reactions, the molecularity of the reaction step is equal to the order of the reaction with respect to each reactant participating in that step. This is because the stoichiometric coefficients in the balanced equation for the elementary step directly determine the order with respect to each reactant.
- However, for complex (non-elementary) reactions involving multiple steps and intermediates, the order may not necessarily correspond to the molecularity of any individual step. In such cases, the order is determined experimentally, while the molecularity applies only to the individual elementary steps.