## 9.99

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

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

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

Rucha Kulkarni 2A
Posts: 43
Joined: Fri Sep 29, 2017 7:05 am

### 9.99

Does anyone know how to solve exercise 9.99?

Thuy-Anh Bui 1I
Posts: 56
Joined: Sat Jul 22, 2017 3:00 am
Been upvoted: 2 times

### Re: 9.99

The dehydrogenation of cyclohexane to benzene is not spontaneous:
C6H12 --> C6H6 + 3H2 ΔG°r = +97.6 kJ/mol
However, if it is paired spontaneous process where a molecule can accept the hydrogen product, the entire process will turn spontaneous. Ethene accepting hydrogen is spontaneous:
C2H4 + H2 --> C2H6 ΔG°r = -100.97 kJ/mol
Mutiply this equation by 3 so that it accepts 3 H2:
3(C2H4 + H2 --> C2H6) ΔG°r = 3(-100.97 kJ/mol) = -302.91 kJ/mol
Combining these reactions makes the overall process spontaneous:
C6H12 + 3C2H4 --> C6H6 + 3C2H6 ΔG°r = -205.31 kJ/mol
This technique is similar to Hess's law. Hope this helps!