## spontaneous reactions

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

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

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

Jasleen Kahlon
Posts: 52
Joined: Wed Nov 21, 2018 12:19 am

### spontaneous reactions

What exactly does a reaction being spontaneous mean in terms of thermodynamics, and what occurs when ∆S and ∆H are either both negative or both positive?

Ashley Wang 4G
Posts: 103
Joined: Wed Sep 11, 2019 12:16 am

### Re: spontaneous reactions

A spontaneous reaction means it will tend to occur under the given conditions without an outside source of energy. Note that it says nothing about the speed of the reaction!

When ∆S and ∆H are either both negative or both positive, that is when the temperature dependence of the reaction becomes very important, as the magnitude of T will determine whether the reaction will be spontaneous.

Hope this helps!

saigorijavolu2k
Posts: 108
Joined: Sat Sep 28, 2019 12:15 am

### Re: spontaneous reactions

A negative delta S means that the reverse reaction is spontaneous. A positive delta S means that the forward reaction is spontaneous. A negative delta H means that it is exothermic and usually exothermic reactions are associated with being spontaneous because they release energy.