Units of ΔS


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RyanTran2F
Posts: 44
Joined: Thu Jul 27, 2017 3:00 am

Units of ΔS

Postby RyanTran2F » Sat Feb 03, 2018 9:21 pm

Why does the answer key sometimes solve for ΔS and say units is J/K but sometimes J/K mol? When do we add on the "per mole" and will we be marked down if we do not have it? Thanks :)

Gianna Apoderado 1B
Posts: 57
Joined: Fri Sep 29, 2017 7:04 am

Re: Units of ΔS

Postby Gianna Apoderado 1B » Sat Feb 03, 2018 10:38 pm

From what I’ve seen, delta S is given in both J/K and J/K•mol-1 depending on the context of what you need it for! (Ive always assumed that the “per mole” is implied)

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

Re: Units of ΔS

Postby Shawn Patel 1I » Sun Feb 04, 2018 9:53 am

Hey,
If J/k mol is given for enthalpy, and there is no value of mol that needs to be accounted for, then the entropy would also be in J/k mol. In some cases, such as when calculating standard reaction entropy, and you are given the amount of moles per product or reactant, then the answer would likely come out as J/k.

RyanTran2F
Posts: 44
Joined: Thu Jul 27, 2017 3:00 am

Re: Units of ΔS

Postby RyanTran2F » Sun Feb 04, 2018 11:36 am

Shawn Patel 1I wrote:Hey,
If J/k mol is given for enthalpy, and there is no value of mol that needs to be accounted for, then the entropy would also be in J/k mol. In some cases, such as when calculating standard reaction entropy, and you are given the amount of moles per product or reactant, then the answer would likely come out as J/k.


Well that was what I thought but when the answer key calculates standard reaction entropy, the answer has a per mole. When it uses qrev/T then it is just J/K. Thanks :)


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