Keq & Sponteneity

[Graffiti]

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Could anyone explain the relationship between Keq and delta G? I'm reading TBR thermo chapter and they don't really seem to emphasize the differences between the two and it's really confusing me. What is the relationship between spontaneity and Keq?

 

[GreenRabbit]

deltaG is change in free energy, negative is spontaneous. Keq is equilibrium constant. They are related by the equation: deltaG = -RTlnK

As you can see, when K is less than 1 (reactants favored), deltaG is positive and therefore we say the reaction is not spontaneous. When K is greater than 1 (products favored), G is negative and we say the reaction is spontaneous.

 

[Graffiti]

deltaG is change in free energy, negative is spontaneous. Keq is equilibrium constant. They are related by the equation: deltaG = -RTlnK

As you can see, when K is less than 1 (reactants favored), deltaG is positive and therefore we say the reaction is not spontaneous. When K is greater than 1 (products favored), G is negative and we say the reaction is spontaneous.

yeah but is it regular delta G or only for delta G naught is this true? or both?

Also, in a reaction coordinate diagram, the free energy... is that delta G naught or regular delta G. In other words, in a reaction coordinate diagram, if the free energy is negative, is it safe to say keq > 1 (and vice versa for a nonspontaenous rxn)?

 

[GreenRabbit]

yeah but is it regular delta G or only for delta G naught is this true? or both?

Also, in a reaction coordinate diagram, the free energy... is that delta G naught or regular delta G. In other words, in a reaction coordinate diagram, if the free energy is negative, is it safe to say keq > 1 (and vice versa for a nonspontaenous rxn)?

Since delta G naught just means standard conditions, it would be delta G naught if your Keq is given under standard conditions. It would be delta G for any other conditions (with Keq for those conditions).

The reaction coordinate diagram can be given for any temperature and pressure, again it depends on whether the conditions are standard.