What is the relationship between exergy and Gibbs free energy?

[Nikitin]

Hi. I have two questions:

1) Is -ΔG the amount of useful work a system can do while the pressure and temperature of the surroundings are constant?

2) Is exergy = -ΔG only if the pressure and temperature of the system and surroundings is constant?

thanks

 

[dauto]

What is exergy?

 

[Nikitin]

It's defined as the theoretical maximum work a system can do when moving towards thermal equilibrium.

I'm just unsure about the specifics behind its definition.

http://en.wikipedia.org/wiki/Exergy