What is the Difference Between Free Energy and Standard Free Energy?

The difference between free energy and standard free energy lies in the conditions under which they are calculated.

Free Energy (Gibbs Free Energy):

• Gibbs free energy is a thermodynamic quantity that combines enthalpy and entropy into a single value.
• It is a measure of the potential work that can be extracted from a system under constant temperature and pressure.
• The change in Gibbs free energy (ΔG) is related to the sum of the change in enthalpy (ΔH) and the product of temperature (T) and the change in entropy (ΔS).

Standard Free Energy (ΔG°):

• Standard free energy is the Gibbs free energy at standard conditions, which are typically 25°C (298 K) and 1 atm pressure.
• It is used to compare different reactants and products in their standard states.
• The standard free energy change (ΔG°) is related to the standard enthalpy change (ΔH°), the standard entropy change (ΔS°), and the temperature (T) by the equation: ΔG° = ΔH° - TΔS°.

In summary, Gibbs free energy (ΔG) depends on the experimental conditions, while standard free energy (ΔG°) is calculated under standard conditions (25°C and 1 atm pressure). Standard free energy is used to compare different systems at their standard states, making it easier to predict the spontaneity of chemical reactions and the amount of work that can be extracted from them.

Comparative Table: Free Energy vs Standard Free Energy

Here is a table comparing free energy and standard free energy:

In summary, free energy is a measure of the available energy in a system, while standard free energy specifically refers to the free energy change for a process under standard conditions, such as 298 K and 1 atm.