## Quiz 1 Preparation Question (Gibbs Free Energy?)

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

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

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

Steph S 2F
Posts: 10
Joined: Fri Sep 26, 2014 2:02 pm

### Quiz 1 Preparation Question (Gibbs Free Energy?)

There is a question in the Winter 2014 quiz preparation that asks us to determine if a reaction is spontaneous, and a what temperature.

Cl2(g) ---> 2Cl(g)

The answer states that the reaction is spontaneous at high temperatures. I understand why ΔS would be positive, but why is ΔH positive in this reaction?

jennifer_zhou2C
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Question (Gibbs Free Energy?)

Bonds are being broken, so it is endothermic. The delta H would be positive.

Andrew Afyouni
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Question (Gibbs Free Energy?)

Energy is required to separate intermolecular forces holding bonds together...these bonds include hydrogen bonds, dipole dipole interactions, and London dispersion forces. Adding energy to the system is required to facilitate the breaking of these interactions and thus the heat at constant pressure (enthalpy) of the system is positive. Hope this helps!