## 11.83

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

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

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

Kathleen Vidanes 1E
Posts: 62
Joined: Fri Sep 29, 2017 7:07 am

### 11.83

Why is it that if we want the equilibrium constant at two temperatures, we need to calculate the delta H(standard) and the delta S(standard)? Why can't we just use the equation delta G(standard) = -RTlnK and replace the T depending on the equilibrium constant that we are solving for?

Ishan Saha 1L
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

### Re: 11.83

Hi,
In this problem we actually use both of those methods to ultimately solve for k at each temperature. We cannot directly use the equation delta G(standard) = -RTlnK because we do not know G(standard) in 11.83. Thus we need to solve for it using the formula delta G(standard)= delta H(standard)- T*delta S(standard), and then we can use delta G(standard) = -RTlnK to solve for K.

Hope this helped!