Molecularity

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Payton Kammerer 2B
Posts: 49
Joined: Tue May 01, 2018 3:00 am

Molecularity

I'm a little confused on the definition of molecularity. Or I suppose, the definition of "species"
Is a species a single molecule, or is it a single type of molecule? I may be confused because in biology, a species is a type of organism, but this definition seems to have little to do with that. In an elementary step in which two NO molecules collide, is that one or two species?

Brian_Ho_2B
Posts: 221
Joined: Fri Aug 09, 2019 12:16 am

Re: Molecularity

Molecularity accounts for both the number of different types of species as well as their stoichiometric coefficients. For instance, if an elementary step had something like: 2A + B --> something, the molecularity is termolecular, because in total, there are three molecules involved.

Justin Sarquiz 2F
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: Molecularity

A species in this case refers to the number of reactants. In the example you gave, this is bimolecular. The number of moles of reactants determines the molecularity.

Posts: 113
Joined: Thu Jul 11, 2019 12:16 am

Re: Molecularity

The textbook defines molecularity as the number of reactant moles, atoms, or ions taking part in a specified elementary reaction.

Christineg1G
Posts: 115
Joined: Fri Aug 09, 2019 12:15 am
Been upvoted: 1 time

Re: Molecularity

Molecularity would be the number of molecules or species in an elementary step, and also determine the rate. Rate law for each elementary steps comes directly from molecularity.