Free energy change (ΔG)

Definition

Free energy change ($\Delta G$) is the difference in free energy between the products and reactants in a chemical reaction. It determines whether a process is spontaneous or non-spontaneous.

5 Must Know Facts For Your Next Test

1. $\Delta G$ is calculated using the equation $\Delta G = \Delta H - T\Delta S$, where $\Delta H$ is the change in enthalpy, $T$ is the temperature in Kelvin, and $\Delta S$ is the change in entropy.
2. A negative $\Delta G$ indicates a spontaneous reaction, while a positive $\Delta G$ indicates a non-spontaneous reaction.
3. At equilibrium, $\Delta G = 0$, meaning there is no net change in free energy.
4. $\Delta G^0$, standard free energy change, refers to conditions where reactants and products are at standard state concentrations (1 M concentration for solutions, 1 atm pressure for gases).
5. $\Delta G$ can predict reaction direction but not rate; kinetic factors must be considered separately.

Review Questions

Related terms

Enthalpy ($\Delta H$): The total heat content of a system, used to quantify heat changes during chemical reactions.

Entropy ($\Delta S$): A measure of disorder or randomness in a system.

$K_{eq}$: The equilibrium constant that expresses the ratio of product concentrations to reactant concentrations at equilibrium.