Spontaneity in regards to enthalpy and entropy






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Nane Onanyan 1G
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Spontaneity in regards to enthalpy and entropy

Postby Nane Onanyan 1G » Wed Mar 10, 2021 10:45 pm

When deltaH is positive and deltaS is positive, the reaction is spontaneous above a certain temperature.

Does this mean that for the reverse reaction, the reaction is spontaneous below a certain temperature? If yes, is that always the case?

Marc Lubman 3B
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Re: Spontaneity in regards to enthalpy and entropy

Postby Marc Lubman 3B » Wed Mar 10, 2021 11:01 pm

I think yes, both are correct, because the reverse reaction will have a negative enthalpy change and a negative entropy change, so whether the enthalpy change is negative enough to overcome the positive value of -TdeltaS will depend on whether the T value is low enough.

edward_brodell_2I
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Re: Spontaneity in regards to enthalpy and entropy

Postby edward_brodell_2I » Fri Mar 12, 2021 9:17 pm

Since deltaG = deltaH - TdeltaS if we see that the reverse reaction will result in an opposite -deltaH and since TdeltaS is negative at a temperature it will be favorable.

Yichen Fan 3A
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Re: Spontaneity in regards to enthalpy and entropy

Postby Yichen Fan 3A » Fri Mar 12, 2021 10:01 pm

Yeah, for the reverse reaction you will just have negative deltaH and deltaS which if you put into deltaG = deltaH - TdeltaS, it will be a spantaneous reaction below certain temperature.


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