enthalpy and entropy when it comes to spontaneous reactions

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Michelle Chernyak 1J
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Joined: Fri Sep 29, 2017 7:06 am

enthalpy and entropy when it comes to spontaneous reactions

Postby Michelle Chernyak 1J » Sun Feb 04, 2018 8:08 pm

What carries more weight when determining if a reaction is spontaneous, the enthaply of the reaction (if it is endothermic or exothermic) or the entropy of the reaction? Or do they carry the same weight?

Angel Ni 2K
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

Re: enthalpy and entropy when it comes to spontaneous reactions

Postby Angel Ni 2K » Sun Feb 04, 2018 8:13 pm

It depends on the temperature.

AnuPanneerselvam1H
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Joined: Fri Sep 29, 2017 7:07 am

Re: enthalpy and entropy when it comes to spontaneous reactions

Postby AnuPanneerselvam1H » Sun Feb 04, 2018 9:14 pm

Spontaneity is determined by multiplying temperature (in kelvin) and enthalpy and subtracting this from entropy. If this value is negative, the reaction is spontaneous.

Emma Li 2C
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Re: enthalpy and entropy when it comes to spontaneous reactions

Postby Emma Li 2C » Sun Feb 04, 2018 9:20 pm

Both affect! Spontaneity depends on whether or not delta G is negative, so I think any combination of positive/negative enthalpy and positive/negative entropy (except when enthalpy is positive and entropy is negative) can produce a spontaneous reaction if it makes delta G negative.

Nathan Tu 2C
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Joined: Fri Sep 29, 2017 7:07 am

Re: enthalpy and entropy when it comes to spontaneous reactions

Postby Nathan Tu 2C » Sun Feb 04, 2018 9:43 pm

Both affect whether the reaction is spontaneous. Since gibbs free energy is dependent on the enthalpy and entropy, they both help determine whether the reaction is spontaneous. Given certain combinations of enthalpy and entropy values, the temperature can help determine whether the reaction is spontaneous.

Scott Chin_1E
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Joined: Sat Jul 22, 2017 3:00 am

Re: enthalpy and entropy when it comes to spontaneous reactions

Postby Scott Chin_1E » Sun Feb 04, 2018 9:48 pm

A quick correction to the post regarding the equation to determine DeltaG and thus spontaneity:
Instead of multiplying temperature and change in enthalpy and subtracting the product from entropy, it is actually

deltaG = deltaH - (temperature)(deltaS)

Kayla Tchorz-Dis 1F
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Joined: Thu Jul 13, 2017 3:00 am

Re: enthalpy and entropy when it comes to spontaneous reactions

Postby Kayla Tchorz-Dis 1F » Sun Feb 04, 2018 11:01 pm

the value of temperature plays a great deal into the spontaneity of the reaction. The sign of the delta H and the delta also influences the ultimate sign of delta G, so it is somewhat a case to case basis. Neither one over the other influences it more.


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