## why/how do molar gibbs free energies change?

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

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

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

Sue Bin Park 2I
Posts: 52
Joined: Mon Jun 17, 2019 7:24 am

### why/how do molar gibbs free energies change?

the textbook has this passage in 4j.2, pg 332:

"The molar Gibbs free energy of a substance in a mixture depends on what molecules it has as neighbors, so the molar Gibbs free energies of NH3, N2, and H2 change as the reaction proceeds. For example, at an early stage of the reaction, an NH3 molecule has mostly N2 and H2 molecules around it, but at a later stage of the reaction, most of its neighbors may be NH3 molecules."

how/why exactly does this occur? what do neighbouring molecules have to do with one species' molar gibbs free energy? i feel like its definitely hinting at the fact that deltaG = 0 at equilibrium, but the textbook doesn't really explain the mechanics of why the above statement is true.

Angela Patel 2J
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

### Re: why/how do molar gibbs free energies change?

I'm not 100% sure, but it probably has to do with changes in entropy. Different molecular compositions for a solution would probably change entropy (and therefore gibbs free energy) as there would be a different number of states. I'm guessing that for the midterm we don't have to understand this exact concept of gibbs free energy changing in a solution.