Gibbs Free Energy

Definition

Gibbs free energy is a thermodynamic potential that measures the maximum reversible work obtainable from a closed system at constant temperature and pressure. It's a key concept in understanding whether a process or reaction can occur spontaneously, as it combines enthalpy, entropy, and temperature into one equation, providing insight into the energy available for doing work.

5 Must Know Facts For Your Next Test

1. Gibbs free energy is defined by the equation $$ G = H - TS $$, where G is Gibbs free energy, H is enthalpy, T is temperature in Kelvin, and S is entropy.
2. A negative change in Gibbs free energy (\(\Delta G < 0\)) indicates that a reaction is spontaneous under constant temperature and pressure conditions.
3. At equilibrium, the change in Gibbs free energy is zero (\(\Delta G = 0\)), meaning there is no net change in the concentrations of reactants and products.
4. Gibbs free energy can be used to calculate equilibrium constants for chemical reactions through the relation $$ \Delta G = -RT \ln K $$, where K is the equilibrium constant.
5. In multi-component systems, Gibbs free energy helps predict phase behavior and stability by assessing how changes in temperature and pressure affect different phases.

Review Questions

• How does Gibbs free energy relate to the spontaneity of chemical reactions?
  • Gibbs free energy determines the spontaneity of chemical reactions by using the relationship between enthalpy, entropy, and temperature. If the change in Gibbs free energy (\(\Delta G\)) is negative, it means that the reaction can occur spontaneously. This relationship highlights how both the energy released or absorbed (enthalpy) and the disorder created (entropy) impact whether a reaction will proceed.
• Discuss how Gibbs free energy applies to phase transitions and phase equilibrium in a system.
  • Gibbs free energy plays a crucial role in understanding phase transitions and phase equilibrium by establishing conditions under which different phases coexist. At equilibrium, the Gibbs free energies of all coexisting phases are equal. During a phase transition, such as melting or boiling, the system will adjust temperature or pressure until the Gibbs free energies align, ensuring stability across phases.
• Evaluate how Gibbs free energy influences reaction yield according to Le Chatelier's principle.
  • Gibbs free energy significantly influences reaction yield as described by Le Chatelier's principle. When external conditions like temperature or pressure are altered, the system adjusts to minimize changes in Gibbs free energy. By predicting shifts in equilibrium based on these changes, it can inform strategies for maximizing product yield in chemical reactions by manipulating conditions to favor reactants or products based on their respective Gibbs energies.

Related terms

Enthalpy:

A thermodynamic quantity equivalent to the total heat content of a system, used to quantify the heat transfer in chemical reactions and phase changes.

Entropy: A measure of the disorder or randomness in a system, which reflects the number of possible microscopic configurations that correspond to a thermodynamic system's macroscopic state.

Phase Equilibrium:

The state at which multiple phases (solid, liquid, gas) coexist in equilibrium, characterized by equal chemical potential across phases.