## Delta G spontaneity

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

deniise_garciia
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### Delta G spontaneity

How can you tell if delta G is spontaneous or non spontaneous when it is Temperature dependent?

Cynthia Aragon 1B
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Joined: Mon Apr 09, 2018 1:38 pm

### Re: Delta G spontaneity

When Delta G is given and you see the standard symbol it means standard temperature which is 298K. Also 1M and 1Atm is standard. Delta G is spontaneous when Delta H is positive and and Delta S is positive. Also, Delta G is spontaneous when both Delta H and Delta s are negative.

Delta G is non-spontaneous when both Delta H and Delta S are positive. Moreover, it can be that both Delta H and Delta S are negative.

Positive meaning favorable which increases entropy and negative meaning unfavorable which decreases entropy.

Posts: 63
Joined: Fri Sep 28, 2018 12:19 am

### Re: Delta G spontaneity

As a side note, you can further solve for when it becomes spontaneous by setting the equation equal to zero and solving for T.

Jocelyne Milke 1G
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### Re: Delta G spontaneity

Here's a picture that may help.
Attachments

yuetao4k
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### Re: Delta G spontaneity

When you plug in the temperature and other variables, as long as delta G is negative, then the reaction is spontaneous.

Celio_G_Dis2C
Posts: 33
Joined: Fri Jan 11, 2019 12:16 am

### Re: Delta G spontaneity

When delta H and delta S have differing signs then the reaction is temperature dependent

Celio_G_Dis2C
Posts: 33
Joined: Fri Jan 11, 2019 12:16 am

### Re: Delta G spontaneity

"Delta G is non-spontaneous when both Delta H and Delta S are positive. Moreover, it can be that both Delta H and Delta S are negative. " is not correct. It MAY become nonspontaneous

Nghi Nguyen 2L
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Joined: Fri Sep 28, 2018 12:18 am

### Re: Delta G spontaneity

you really just have to look at delta G in relation to the other variables such as delta H, delta S, and T
knowing their signs will help you determine whether or not delta G is positive or negative, thus giving you spontaneity

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