Gibbs free energy is a measure of the spontaneity of a chemical reaction. It is the chemical potential for a reaction and is minimized at equilibrium. The change in Gibbs free energy can be calculated by ΔG°_rxn = ΔH°_rxn - TΔS°_rxn where ΔG°_rxn is:

• A. the standard enthalpy change of the reaction
• B. the standard entropy change of the reaction
• C. the standard Gibbs free energy change of the reaction
• D. the equilibrium constant of the reaction

Answer: (C)

Verified step by step guidance

1. Begin by understanding the Gibbs free energy equation: ΔG°_rxn = ΔH°_rxn - TΔS°_rxn. This equation relates the change in Gibbs free energy (ΔG°_rxn) to the change in enthalpy (ΔH°_rxn), temperature (T), and change in entropy (ΔS°_rxn).
2. Identify each term in the equation: ΔG°_rxn represents the standard Gibbs free energy change of the reaction, ΔH°_rxn is the standard enthalpy change, T is the temperature in Kelvin, and ΔS°_rxn is the standard entropy change.
3. Recognize that the Gibbs free energy change (ΔG°_rxn) indicates the spontaneity of a reaction. A negative ΔG°_rxn suggests that the reaction is spontaneous under standard conditions.
4. Understand that at equilibrium, the Gibbs free energy is minimized, meaning ΔG°_rxn approaches zero, and the reaction is at a state where the forward and reverse reactions occur at the same rate.
5. Relate the Gibbs free energy change to the equilibrium constant (K) using the equation ΔG°_rxn = -RT ln(K), where R is the universal gas constant and T is the temperature. This shows how Gibbs free energy is connected to the equilibrium constant of the reaction.