## Temperature and Spontaneity

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

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

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

Lisa Tang 1C
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Joined: Fri Sep 29, 2017 7:05 am
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### Temperature and Spontaneity

Is it true that when $\Delta$H and $\Delta$S are both negative that decreasing the temperature increases spontaneity? If so, could someone explain why this is the case? I know it has to do with the equation $\Delta$G=$\Delta$H-T$\Delta$S, but beyond the math, what is the explanation?

Katie Lam 1B
Posts: 52
Joined: Fri Sep 29, 2017 7:06 am

### Re: Temperature and Spontaneity

If both delta H and delta S are negative, the reaction is only spontaneous at low temperatures since the T delta S part of the equation will be overall positive. In order for a reaction to be spontaneous, then, the negative delta H needs to be of larger magnitude than the positive T delta S so that delta G is negative.

Jessica Benitez 1K
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: Temperature and Spontaneity

The chart we went over in lecture goes:
Delta S (+) and Delta H (-) means spontaneous at all temperatures
Delta S (+) and Delta H (+) means spontaneous at high temperatures
Delta S (-) and Delta H (-) means spontaneous at low temperatures
Delta S (-) and Delta H (+) means not spontaneous at any temperatures, however, the reverse process is spontaneous

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