Standard free energy of formation ΔGf°

Definition

The standard free energy of formation, $\Delta G_f^\circ$, is the change in Gibbs free energy when 1 mole of a compound is formed from its elements in their standard states at 1 atm pressure and 298.15 K (25°C). It indicates the thermodynamic stability of the compound relative to its elements.

5 Must Know Facts For Your Next Test

1. The standard free energy of formation for any element in its most stable form is zero.
2. A negative $\Delta G_f^\circ$ indicates that the formation of the compound is spontaneous under standard conditions.
3. A positive $\Delta G_f^\circ$ means that the compound is not spontaneously formed from its elements under standard conditions.
4. $\Delta G_f^\circ$ can be used to calculate the Gibbs free energy change for a reaction using Hess's Law.
5. The units of $\Delta G_f^\circ$ are typically kJ/mol.

Related terms

Gibbs Free Energy:

A thermodynamic potential that measures the maximum amount of reversible work performed by a system at constant temperature and pressure.

Standard State: A reference state for a specific substance defined by a set of conventional standards such as 1 atm pressure and 298.15 K temperature.

Hess's Law:

States that the total enthalpy change during the complete course of a chemical reaction is the same regardless of the steps taken or pathway followed.