# Re: Units for deltaS of Reaction

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Determine the value of the entropy change, deltaS rxn for the combustion of CO (g) at 298 K...

According to Collegeboard (the question came from an old FRQ), the answer's units are J/mol K, which is what I wrote. However, my chem teacher says the units are incorrect (and took a point off my test -.-), and I've noticed that entropy's usually written in J/K.

What's the difference between deltaS rxn and normal S, and the difference between J/K and J/mol K? (And who's correct -- Collegeboard or my teacher?)

Thanks :).

### Re: Units for deltaS of Reaction

As far as I am aware, entropy is measured in J/K and this would apply to a reaction.

[delta]S = S products - Sreactants.

So S for the reaction should be in J/K

There is a term called molar entropy which is measured in J/mol K

'Chemistry is not just the study of matter; Chemistry is the study which matters!' - Kingchemist

### How's it going, are the units

How's it going, are the units of molar entropy(J/mol K)  actually J*K/mol  or  J/(mol*K) ?

### molar entropy units are  J/

molar entropy units are  J/(mol*K)