## Molecularity

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Drew Myers 4G
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Molecularity

What is molecularity?

Sean Cheah 1E
Posts: 105
Joined: Wed Sep 18, 2019 12:20 am

### Re: Molecularity

Molecularity describes the number of reactant molecules that are required to collide in each elementary step of a reaction. Elementary steps that involve only a single reactant molecule are unimolecular, those that involve two are bimolecular, three termolecular, and so on. Note that molecularity depends on the number of molecules not the number of distinct compounds (e.g. 2NO --> N2O2 is bimolecular because there are 2 NO reactant molecules). Additionally, note that molecularity is not defined for multi-step reactions, though one can consider the molecularity of each of the individual elementary steps that make up the overall reaction.

Aman Sankineni 2L
Posts: 103
Joined: Fri Aug 30, 2019 12:17 am

### Re: Molecularity

The molecularity of a reaction is defined as the number of molecules or ions that participate in the rate-determining step.

asannajust_1J
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### Re: Molecularity

unimolecular would correspond with 1 molecule that initiates the reaction
bimolecular would correspond with 2 molecules colliding to start a reaction
termolecular would correspond with 3 molecules colliding
and higher molecularity is very rare

Micah3J
Posts: 100
Joined: Tue Oct 08, 2019 12:16 am

### Re: Molecularity

asannajust_1J wrote:unimolecular would correspond with 1 molecule that initiates the reaction
bimolecular would correspond with 2 molecules colliding to start a reaction
termolecular would correspond with 3 molecules colliding
and higher molecularity is very rare

Termolecular can also be 2 of the same molecules colliding with a separate molecule. [A] + [A] + [B] -> [P]