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### G at minimum

Posted: Sat Feb 03, 2018 8:02 pm
Why can there no longer be any change in a system when G (Gibbs free energy) is at a minimum?

### Re: G at minimum

Posted: Sat Feb 03, 2018 8:09 pm
Gibbs free energy is essentially a measure of how much energy we can get from a system. So if the free energy is at a minimum, then the reaction is at equilibrium and no more change in energy can be done in the system. If anyone would like to add, please feel free.

### Re: G at minimum

Posted: Sat Feb 03, 2018 10:04 pm
So if Gibbs Free Energy is at a maximum or minimum, it means that the reaction is at equilibrium?

### Re: G at minimum

Posted: Sat Feb 03, 2018 10:13 pm
When G is at minimum, the reaction is at equilibrium so the system shouldn't have any tendency to do work spontaneously.

### Re: G at minimum

Posted: Sat Feb 03, 2018 10:18 pm
The graph for Gibbs Free Energy that we learned in lecture was the graph with the minimum. So I'm not too sure what you mean by when it is at a maximum it's at equilibrium. But I think the graph we learned is a good explanation.
When the ball is anywhere on the graph other than the lowest point, it will roll down to the lowest point. The higher the ball is, the more available energy there is to do work. I don't think there's ever a maximum unless you want to think about how much energy a reaction can actually produce but that goes into specific reactions because no two are the same. Once the ball has reached the bottom, it won't roll anymore; the ball is essentially not able to do anything anymore and this is where there is no energy left to do work which we call equilibrium.

### Re: G at minimum

Posted: Sun Feb 04, 2018 12:01 am
I like to also think about the fact that equilibrium is measured where the change in G is equal to 0. This also explains why negative G values are spontaneous, because they are approaching a lower number (where dG=0). If there is less free energy it is safe to assume that there is less potential for work.

### Re: G at minimum

Posted: Sun Feb 04, 2018 1:28 pm
How come the system isn't necessarily at equilibrium when delta G naught is zero?