key term - ΔG_f°

Definition

ΔG_f° is the standard Gibbs free energy of formation, which is a measure of the spontaneity and feasibility of a chemical reaction. It represents the change in Gibbs free energy that occurs when a substance is formed from its constituent elements in their standard states.

5 Must Know Facts For Your Next Test

1. ΔG_f° is negative for spontaneous and favorable reactions, and positive for non-spontaneous and unfavorable reactions.
2. The more negative the value of ΔG_f°, the more favorable and spontaneous the reaction is.
3. ΔG_f° can be used to calculate the equilibrium constant (K) of a reaction using the relationship: ΔG_f° = -RT ln K.
4. ΔG_f° is an intensive property, meaning it does not depend on the amount of the substance involved in the reaction.
5. The standard Gibbs free energy of formation is a key parameter in determining the feasibility and direction of chemical reactions.

Review Questions

• Explain the relationship between ΔG_f° and the spontaneity of a chemical reaction.
  • The standard Gibbs free energy of formation, ΔG_f°, is a measure of the spontaneity and feasibility of a chemical reaction. If ΔG_f° is negative, the reaction is spontaneous and favorable, meaning it will occur naturally without the input of external work. Conversely, if ΔG_f° is positive, the reaction is non-spontaneous and unfavorable, requiring the input of energy to proceed. The more negative the value of ΔG_f°, the more spontaneous and favorable the reaction is.
• Describe how ΔG_f° can be used to calculate the equilibrium constant (K) of a reaction.
  • ΔG_f° is related to the equilibrium constant (K) of a reaction through the equation: ΔG_f° = -RT ln K, where R is the universal gas constant and T is the absolute temperature. This relationship allows you to determine the equilibrium constant of a reaction if you know the standard Gibbs free energy of formation, or vice versa. By knowing the value of ΔG_f°, you can calculate the equilibrium constant and predict the extent to which a reaction will proceed at equilibrium.
• Analyze the significance of ΔG_f° as an intensive property in the context of chemical reactions.
  • The standard Gibbs free energy of formation, ΔG_f°, is an intensive property, meaning it does not depend on the amount of the substance involved in the reaction. This is important because it allows you to use ΔG_f° to determine the feasibility and spontaneity of a reaction without needing to know the specific quantities of the reactants and products. The intensive nature of ΔG_f° makes it a valuable tool for understanding and predicting the behavior of chemical systems, as it provides a universal measure of the driving force behind a reaction that is independent of the scale or size of the system.

Related terms

Gibbs Free Energy:

Gibbs free energy is a thermodynamic quantity that combines the concepts of enthalpy and entropy to determine the spontaneity and feasibility of a process.

Standard State: The standard state is a reference condition for a substance, typically at 25°C and 1 atm pressure, used to define and measure thermodynamic properties.

Spontaneity:

Spontaneity refers to the natural tendency of a process to occur without the input of external work, driven by a decrease in Gibbs free energy.