### Endothermic Favorable?

Posted:

**Tue Feb 13, 2018 10:33 pm**Why are endothermic reactions not favorable at high temperatures?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=135&t=27766

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Posted: **Tue Feb 13, 2018 10:33 pm**

Why are endothermic reactions not favorable at high temperatures?

Posted: **Tue Feb 13, 2018 10:40 pm**

If you have an endothermic reaction, that means Delta H is positive. Delta S depends. If Delta S was positive, then by Delta G = Delta H - T*Delta S, the reaction would be favorable at high temperatures. If Delta S was negative, then the reaction would not be favorable at any temperature.

Posted: **Tue Feb 13, 2018 11:28 pm**

Look at the equation delta G = delta H - T(delta S)

If a reaction is endothermic then delta H will be positive. It depends whether delta S is negative or positive, and whether T is a high or low value to determine whether delta G will be negative (which would mean the reaction is favorable). If Delta S is negative, that means delta G would never be negative as a positive delta H minus a negative T times Delta S would always be positive. If Delta S is positive, than T would have to be high enough to make T times delta S a greater value than delta H, thus making delta G negative as well.

If a reaction is endothermic then delta H will be positive. It depends whether delta S is negative or positive, and whether T is a high or low value to determine whether delta G will be negative (which would mean the reaction is favorable). If Delta S is negative, that means delta G would never be negative as a positive delta H minus a negative T times Delta S would always be positive. If Delta S is positive, than T would have to be high enough to make T times delta S a greater value than delta H, thus making delta G negative as well.