## Which equation to use

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

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

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

Dong Hyun Lee 4E
Posts: 68
Joined: Fri Sep 28, 2018 12:23 am

### Which equation to use

I'm confused on which equation is used in which situation as I know most of the textbook questions use the equation (change in g= change in h - t * change in s) so when do we use G= -RT ln(k)?

Natalie Liu 4I
Posts: 62
Joined: Fri Sep 28, 2018 12:29 am

### Re: Which equation to use

I think most likely when the question includes equilibrium constants or reaction quotients it could be an indicator to use the equation.

Kobe_Wright
Posts: 83
Joined: Fri Sep 28, 2018 12:16 am

### Re: Which equation to use

Youd use that when they are asking about equilibrium onstants, G=gstandard+RTln(q) when not at equilibrium, G=Gstan+RTln(p) when talking about pressure, and G=-RTln(k) when talking about equilibrium constant.