Spontaneity question

$\Delta S = \frac{q_{rev}}{T}$

Mike Matthews 1D
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am

Spontaneity question

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
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

Re: Spontaneity question

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
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

Re: Spontaneity question

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
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

Re: Spontaneity question

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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Joined: Fri Sep 29, 2017 7:04 am

Re: Spontaneity question

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

Riya Pathare 2E
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Joined: Sat Jul 22, 2017 3:01 am
Been upvoted: 1 time

Re: Spontaneity question

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

Nate O 2L
Posts: 15
Joined: Fri Sep 29, 2017 7:06 am

Re: Spontaneity question

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
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

Re: Spontaneity question

dG=dH-TdS
keep dG negative to maintain spontaneity