Unimolecular vs Bimolecular

[Ruby Sanchez 1K]

How can we tell whether a mechanism is unimolecular or bimolecular?

[Jasmine Sanchez 1K]

A unimolecular reaction will have a single reactant while a bimolecular reaction will have 2 reactants.

[Denise Mora 1C]

A mechanism will be unimolecular if there is only one molecule in the reactants for the rate-determining step. Usually, unimolecular reactions are involved with the decomposition of a molecule into single atoms. EX: O3--> O2 + O, in the reactants side there was only 1 reactant.
A mechanism will be bimolecular when there are two molecules on the reactant side in the rate-determining step, so two reactants form to make a product. EX: NO+NO-->N202, there are 2 reactant molecules in the reactant side to form N202.

[Brandon Li]

Look at the equation. unimolecular = 1 reactant and bimolecular = 2 reactants and termolecular = 3 reactants and so on

[806205379]

The molecularity of a reaction mechanism, whether it's unimolecular or bimolecular, depends on the number of reactant molecules involved in the rate-determining step of the reaction. For a unimolecular reaction mechanism: The rate-determining step involves only one reactant molecule. The rate law for the overall reaction is typically first-order with respect to that reactant. For a bimolecular reaction mechanism: The rate-determining step involves two reactant molecules coming together and colliding in a single step. The rate law for the overall reaction is typically second-order with respect to one reactant (if both reactants are involved in the rate-determining step, the overall reaction could be second-order with respect to both). To determine whether a mechanism is unimolecular or bimolecular, you would need to examine the proposed mechanism and identify the step that determines the rate of the reaction. If that step involves only one reactant molecule, it's likely a unimolecular mechanism. If it involves two reactant molecules colliding, it's likely a bimolecular mechanism.

[Kai Johnson 3B]

To add onto this a third order reaction would be called termolecular which is important to know as we have looked at third order rates before.