## Exercise 9.63

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

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

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

Rucha Kulkarni 2A
Posts: 43
Joined: Fri Sep 29, 2017 7:05 am

### Exercise 9.63

Does anyone know how to solve exercise 9.63 on the homework?

Anna Li 2E
Posts: 21
Joined: Sat Jul 22, 2017 3:00 am

### Re: Exercise 9.63

I'm guessing you use Appendix A to check each molecule's gibb's free energy to see which ones have a positive free energy. Positive free energy corresponds with unstable molecules.

This topic was also answered by Chem_Mod at this thread if you are still confused:
viewtopic.php?f=135&t=19252

Nishma Chakraborty 1J
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

### Re: Exercise 9.63

Hey!

So, the question is asking which of the four compounds are stable compared to their individual elements. If a value of free energy is positive, that means that the compound is unstable with regards to its individual elements. Basically, that reaction is endothermic-- you have to put in heat/energy to bring the elements together. So, compounds with a negative value of free energy indicate that the reaction is favorable, and the elements want to form a bond in order to become more stable, and will release energy.

a) PCl5 and d)SO2 are the answer because they have negative delta G values.

Hope this helps :)