## 9.63

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

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

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

Kaylin Krahn 1I
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### 9.63

Why is it that the compounds with a positive free energy of formation are unstable with respect to the elements?

Kelly Kiremidjian 1C
Posts: 62
Joined: Fri Sep 29, 2017 7:04 am

### Re: 9.63

Thermodynamic stability occurs when a system is in its lowest energy state. Therefore, compounds with positive free energy are said to be unstable while compounds with negative free energy are said to be stable.

Sally Nason - 1K
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Joined: Fri Sep 29, 2017 7:05 am

### Re: 9.63

If the value for delta G is negative then energy needs to be added in order to form the compound so therefore it would not be stable, as it doesn't occur spontaneously. However, a negative delta G for a compound means the compound can form without any stimulus or added energy and is therefore a stable compound.

Janine Chan 2K
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Joined: Fri Sep 29, 2017 7:04 am

### Re: 9.63

In order for decomposition of compounds into their elements to be stable, ∆G of decomposition would have to be (+) aka it won't spontaneously break down. Since decomposition is the opposite of formation, ∆Gf would have to be (-). In other words, the formation is spontaneous and the decomposition is not spontaneous (and thus stable).

Kevin Tabibian 1A
Posts: 42
Joined: Fri Sep 29, 2017 7:06 am

### Re: 9.63

A negative change in Gibbs free energy means that the product will be spontaneously favoured and therefore more stable