## Equations to use

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

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

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

Alana Sur 3B
Posts: 61
Joined: Fri Sep 28, 2018 12:25 am

### Equations to use

When calculating change in Gibbs free energy, when do we use the equation with change entropy and enthalpy and when do we use the gibbs free energy of formation of products and reactants? In the textbook (6th ed), the questions just say refer to appendix 2A but some of the solutions use entropy and enthalpy and the others use gibbs free energy of formation

josie 1C
Posts: 18
Joined: Fri Sep 28, 2018 12:19 am

### Re: Equations to use

it just depends on the information you're given in the problem

Kessandra Ng 1K
Posts: 67
Joined: Fri Sep 28, 2018 12:25 am

### Re: Equations to use

If the problem asks you about different temperatures, for example, and you had to find ∆H and ∆S in the previous parts, then you would use ∆G = ∆H - T∆S. Otherwise, if they give you the values for ∆Gf for the products and reactants, you would use the other equation instead.