What is the Difference Between Gibbs Free Energy and Helmholtz Free Energy?
🆚 Go to Comparative Table 🆚Gibbs free energy and Helmholtz free energy are both thermodynamic functions that describe the energy available for work in a system. However, they differ in their definitions and applications. Here are the key differences between them:
- Definition:
- Gibbs free energy (G) is defined as the energy available to do non-PV work in a thermodynamically-closed system at constant pressure and temperature.
- Helmholtz free energy (F) is defined as the maximum amount of "useful" (non-PV) work that can be extracted from a thermodynamically-closed system at constant volume and temperature.
- Temperature and Pressure:
- Gibbs free energy is related to the energy available at constant pressure, making it applicable to systems where pressure is constant.
- Helmholtz free energy is related to the energy available at constant volume, making it applicable to systems where volume is constant.
- Applications:
- Gibbs free energy is used to study spontaneous reactions and the effect of pressure on these reactions.
- Helmholtz free energy is used to study spontaneous changes in a system and the effect of temperature on these changes.
In summary, Gibbs free energy and Helmholtz free energy are both important thermodynamic functions that describe the energy available for work in a system. They differ in their definitions, with Gibbs free energy related to constant pressure systems and Helmholtz free energy related to constant volume systems. Their applications are also distinct, with Gibbs free energy used to study spontaneous reactions at constant pressure, while Helmholtz free energy is used to study spontaneous changes at constant volume.
Comparative Table: Gibbs Free Energy vs Helmholtz Free Energy
Gibbs free energy and Helmholtz free energy are both thermodynamic potentials that describe the energy available in a system. Here is a table comparing the differences between the two:
| Property | Gibbs Free Energy (G) | Helmholtz Free Energy (F) |
|---|---|---|
| Definition | A measure of the net useful work obtainable from a process at constant pressure and temperature. | A measure of the amount of energy required to create a system at constant temperature and volume. |
| Symbol | G | F |
| Units | Calories or joules | Calories or joules |
| Applicability | More applicable for systems with constant pressure. | Less applicable for systems with constant volume. |
| Work calculations | Represents the maximum amount of reversible work obtainable from a system at constant temperature and constant pressure. | Represents the useful work obtainable from a closed system at constant temperature and constant volume. |
| Entropy | Takes into account the change in entropy (ΔS) for reversible work calculations. | Does not take into account the change in entropy (ΔS) for reversible work calculations. |
In summary, Gibbs free energy represents the maximum amount of reversible work obtainable from a system at constant temperature and pressure, while Helmholtz free energy represents the useful work obtainable from a closed system at constant temperature and volume.
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