Meaning of Free Energy (Gibbs free energy)

In summary, free energy refers to the work done by a system in a reversible isothermal process, excluding any pdV work. It can be represented by either the Gibbs function or the Helmholtz function, depending on the process being considered. This term is commonly used in chemistry thermodynamics and has applications in mechanical engineering.
  • #1
Paulo Bernardo
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Hello everyone, I'm reading some basics of chemistry thermodynamics, and it's hard for me to figure out what is the actual meaning of free energy. could someone please help clarifying this giving specify, real life examples, like applications in mechanical engineering.

Thanks
 
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  • #2
A change in the (i.e.,decrease) in the Gibbs Function, G (free energy) of a system is the work done ( energy freed) in a reversible isothermal-isobaric process exclusive of any pdV work.

The term "free energy" is also applied to the Helmholtz function H whose decrease is the work done by a system in a reversible isothermal process.

Thus G = F - pdV

One should preface free energy with either Gibbs or Helmholtz to avoid confusion.
 

1. What is the definition of free energy?

Free energy, also known as Gibbs free energy, is a thermodynamic quantity that measures the amount of energy available to do work in a system at a constant temperature and pressure.

2. How is free energy related to spontaneity?

The change in free energy of a system, represented by the symbol ΔG, determines whether a reaction or process will occur spontaneously. A negative ΔG indicates that the reaction or process is spontaneous, while a positive ΔG means that it is non-spontaneous.

3. What is the equation for calculating free energy?

The equation for calculating free energy is ΔG = ΔH - TΔS, where ΔH is the change in enthalpy (heat) of the system, T is the temperature in Kelvin, and ΔS is the change in entropy (disorder) of the system.

4. What is the significance of free energy in chemical reactions?

Free energy allows us to predict the direction and spontaneity of chemical reactions. Reactions with a negative ΔG are thermodynamically favorable and will proceed spontaneously, while those with a positive ΔG require an input of energy to occur.

5. How can free energy be affected by temperature and pressure?

Free energy is affected by temperature and pressure through the ΔH and ΔS terms in the equation. An increase in temperature or a decrease in pressure will result in a larger ΔS, making the reaction more favorable. On the other hand, a decrease in temperature or an increase in pressure will lead to a smaller ΔS, making the reaction less favorable.

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