What is the relationship between exergy and Gibbs free energy?

In summary, exergy and Gibbs free energy are both measures of a system's potential energy, with exergy specifically referring to the maximum available work and Gibbs free energy taking into account both potential energy and entropy. Exergy is closely related to thermodynamic efficiency and is affected by factors such as temperature, pressure, and composition. Gibbs free energy is used to determine the spontaneity of a reaction, with a negative value indicating a spontaneous reaction that releases energy.
  • #1
Nikitin
735
27
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
 
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  • #2
What is exergy?
 
  • #3
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
 

Related to What is the relationship between exergy and Gibbs free energy?

1. What is the difference between exergy and Gibbs free energy?

Exergy and Gibbs free energy are both measures of the potential energy of a system. However, exergy specifically refers to the maximum available work that can be obtained from a system as it reaches equilibrium with its surroundings, while Gibbs free energy takes into account both the potential energy and the entropy of the system.

2. How is exergy related to thermodynamic efficiency?

Exergy is closely related to thermodynamic efficiency, as it is a measure of the maximum possible work that can be obtained from a system. A more efficient system will have a higher exergy, as less energy is wasted as heat.

3. What factors affect the exergy of a system?

The exergy of a system is affected by several factors, including temperature, pressure, and the composition of the system. Higher temperatures and pressures generally lead to higher exergy, while the composition of the system can affect the potential for work to be extracted.

4. How is Gibbs free energy used to determine the spontaneity of a reaction?

The change in Gibbs free energy (ΔG) of a reaction is a measure of the amount of energy available to do work. If ΔG is negative, the reaction is considered spontaneous and will proceed without requiring external energy input. If ΔG is positive, the reaction is non-spontaneous and will only occur with an input of energy.

5. Can Gibbs free energy be negative?

Yes, Gibbs free energy can be negative. A negative ΔG indicates that the reaction is spontaneous and releases energy. This can occur when the products of a reaction have a lower energy state than the reactants, and the difference in energy is released as heat or work.

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