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Payton Kammerer 2B
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Postby Payton Kammerer 2B » Sun Mar 08, 2020 11:38 pm

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?

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Re: Molecularity

Postby Brian_Ho_2B » Mon Mar 09, 2020 8:31 am

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
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Re: Molecularity

Postby Justin Sarquiz 2F » Mon Mar 09, 2020 8:32 am

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.

Robin Cadd 1D
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Re: Molecularity

Postby Robin Cadd 1D » Mon Mar 09, 2020 8:34 am

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

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Re: Molecularity

Postby Christineg1G » Mon Mar 09, 2020 9:12 am

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.

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