Gibbs Free Energy

Definition

Gibbs free energy is a thermodynamic quantity that combines the concepts of energy, entropy, and temperature to determine the spontaneity and feasibility of a chemical reaction. It is a critical measure of the driving force behind chemical processes and physical transformations.

5 Must Know Facts For Your Next Test

1. Gibbs free energy, denoted as $G$, is defined as the sum of a system's enthalpy ($H$) and the product of its entropy ($S$) and the absolute temperature ($T$): $G = H - TS$.
2. The change in Gibbs free energy, $\Delta G$, determines the spontaneity and feasibility of a chemical reaction: if $\Delta G < 0$, the reaction is spontaneous; if $\Delta G > 0$, the reaction is non-spontaneous and requires an input of energy.
3. Reactions with $\Delta G = 0$ are at equilibrium, where the forward and reverse reactions occur at the same rate, and there is no net change in the system.
4. Gibbs free energy changes can be used to predict the direction of a reaction and the extent to which it will proceed, as well as to calculate the maximum amount of work a reaction can perform.
5. The magnitude of $\Delta G$ also provides information about the reaction's energy requirements and the degree of spontaneity, with larger negative values indicating more favorable and spontaneous reactions.

Review Questions

• Explain how Gibbs free energy relates to the concept of reaction equilibrium.
  • Gibbs free energy is directly related to the concept of reaction equilibrium. At equilibrium, the change in Gibbs free energy, $\Delta G$, is equal to zero, indicating that the forward and reverse reactions are occurring at the same rate, and there is no net change in the system. If $\Delta G < 0$, the reaction is spontaneous and will proceed towards products; if $\Delta G > 0$, the reaction is non-spontaneous and will require an input of energy to occur. The magnitude of $\Delta G$ also provides information about the degree of spontaneity and the energy requirements of the reaction.
• Describe how Gibbs free energy can be used to predict the feasibility and direction of a chemical reaction.
  • Gibbs free energy can be used to predict the feasibility and direction of a chemical reaction. If the change in Gibbs free energy, $\Delta G$, is negative, the reaction is spontaneous and will occur naturally. Conversely, if $\Delta G$ is positive, the reaction is non-spontaneous and will require an input of energy to proceed. The magnitude of $\Delta G$ also provides information about the degree of spontaneity, with larger negative values indicating more favorable and spontaneous reactions. By calculating $\Delta G$ for a given reaction, you can determine whether the reaction will occur spontaneously, the amount of work it can perform, and the energy requirements for the reaction to proceed.
• Analyze how the concepts of enthalpy, entropy, and temperature are integrated into the Gibbs free energy equation and how this relationship influences the spontaneity and feasibility of a chemical process.
  • The Gibbs free energy equation, $G = H - TS$, integrates the concepts of enthalpy, entropy, and temperature to determine the spontaneity and feasibility of a chemical process. Enthalpy, $H$, represents the total energy of the system, including the energy required to create the system and the energy required to pressurize and heat the system. Entropy, $S$, measures the disorder or randomness of the system, which increases as a reaction proceeds towards equilibrium. Temperature, $T$, is the absolute temperature of the system. The relationship between these three factors, as expressed in the Gibbs free energy equation, determines whether a reaction will occur spontaneously ($\Delta G < 0$), require an input of energy ($\Delta G > 0$), or be at equilibrium ($\Delta G = 0$). This understanding is crucial for predicting the feasibility and direction of chemical processes.

Related terms

Enthalpy:

The total energy of a system, including the energy required to create the system as well as the energy required to pressurize and heat the system.

Entropy:

A measure of the disorder or randomness of a system, which increases as a reaction proceeds towards equilibrium.

Spontaneity: The tendency of a process to occur naturally without the input of external energy, as determined by the sign of the Gibbs free energy change.