## Gibbs free energy of formation

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

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

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

Sanjana Borle 2K
Posts: 111
Joined: Fri Aug 09, 2019 12:15 am

### Gibbs free energy of formation

I dont understand conceptually how the standard Gibbs free energy for pure substances is also zero, like delta H standard. Since the equation for Delta G is H-TdeltaS, why doesnt the TdeltaS part factor in? Why is it still zero?

Mariah
Posts: 104
Joined: Fri Aug 02, 2019 12:16 am

### Re: Gibbs free energy of formation

Sanjana Borle 2K wrote:I dont understand conceptually how the standard Gibbs free energy for pure substances is also zero, like delta H standard. Since the equation for Delta G is H-TdeltaS, why doesnt the TdeltaS part factor in? Why is it still zero?

I think since it is a pure substance you assume that delta S is constant which makes that term zero.

005384106
Posts: 101
Joined: Sat Aug 24, 2019 12:16 am

### Re: Gibbs free energy of formation

How do you know if you are dealing with a pure substance?