Spontaneity question


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Mike Matthews 1D
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Joined: Fri Sep 29, 2017 7:04 am

Spontaneity question

Postby Mike Matthews 1D » Sat Mar 17, 2018 11:19 am

If delta S total is positive can you say that a reaction is spontaneous or is the only way to determine the spontaneity of a reaction through calculating Gibbs free energy?

Isabella Sanzi 2E
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Joined: Thu Jul 13, 2017 3:00 am

Re: Spontaneity question

Postby Isabella Sanzi 2E » Sat Mar 17, 2018 11:34 am

I think the only way to determine spontaneity of a reaction is to calculate the Gibb's Free Energy. Even if you have a large, positive delta S that does not necessarily mean that you will have a negative delta H, and since the equation is deltaG = deltaH - T(deltaS), if the delta H is positive enough, the delta G could be positive, indicating that the reaction would not be spontaneous.

Oscar Valdovinos 1I
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Re: Spontaneity question

Postby Oscar Valdovinos 1I » Sat Mar 17, 2018 1:39 pm

Assuming delta H is postive,
The temperature is high enough it could overcome a positive delta H and make delta G negative (thus a spontaneous reaction). But if temperature is low it doesn't matter if you have a positive delta S, the reaction is not spontaneous.

Justin Bui 2L
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Re: Spontaneity question

Postby Justin Bui 2L » Sat Mar 17, 2018 6:23 pm

Yeah, I'd say it's safest to check it through Gibbs free energy just because the sign of delta G would be able to tell you for sure whether or not something is spontaneous and it's the combination of multiple things apart from just delta S.

Troy Tavangar 1I
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Re: Spontaneity question

Postby Troy Tavangar 1I » Sun Mar 18, 2018 1:13 am

Since deltaH and the temperature affect spontaneity, you must find Gibbs to find if it is spontaneous.

Riya Pathare 2E
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Re: Spontaneity question

Postby Riya Pathare 2E » Sun Mar 18, 2018 10:32 am

Both delta G and delta Stotal can tell you the spontaneity of a reaction

Nate O 2L
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Re: Spontaneity question

Postby Nate O 2L » Sun Mar 18, 2018 3:10 pm

To keep it simple, negative delta G values mean it is spontaneous. You obtain delta G by taking into consideration the enthalpy and entropy values.

Phillip Tran
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Joined: Thu Jul 13, 2017 3:00 am

Re: Spontaneity question

Postby Phillip Tran » Sun Mar 18, 2018 5:02 pm

dG=dH-TdS
keep dG negative to maintain spontaneity


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