Molecularity and Rate Law

[Ryan Aung 2I]

How does molecularity relate to rate law?

[Paul Torres 2I]

Molecularity relates to rate law because it helps determine what the order of the reaction is. When an elementary step has a certain number of atoms in the reactants, the molecularity changes. For instance, when there are two species in the reactants for an elementary step, meaning it is bimolecular or has bimolecular molecularity. Therefore, the rate law is in the second order since there are two species. If there was a singular unimolecular molecularity, then it would be in the first order.

[Lina Shammas]

Hi!

You can determine the molecularity of a reaction using rate law by adding all of the exponents of the concentrations.

For example: k[A][B]

This is bimolecular because the total number of molecules involved is 1+1=2.

Another example: k[A]^2

This is also bimolecular because the total number of molecules involved is 2.

You can just add the exponents, and whatever the sum is lets you know how many molecules are invovled.

[ella3]

The overall reaction order for an elementary reaction will be equal to its molecularity. Molecularity is the number of species involved in an elementary step, or the number of molecules colliding in that step.

Example:

A + A --> P
rate = k[A]^2
Bimolecular
Overall Rxn order = 2 = Bi

or

A + B --> P
rate = k[A][B]
Bimolecular
Overall Rxn order = 2 = Bi

The same trend applies to unimolecular and termolecular reactions!
Hope this helps :)

[Jessica Norman 1B]

Molecularity helps in determining the order of the reaction. If the rate law is in the first phase, it will be unimolecular. If it is in the second, it will be bimolecular. And if it is in the third phase, I believe it will be called termolecular.

[samaagwani-disc2L]

Molecularity relates to rate law because it allows us to determine what the order of the reaction is. Molecularity can change when an elementary step has a certain number of atoms in the reactants. The molecularity can be determined by adding the exponents of the concentrations. For example, k[A]^2 is bimolecular because the total number of molecules involved is two. Another example could be k[A][B]. This would also be bimolecular because 1+1=2. I hope this helps:)