Reaction Gibbs energy and equilibrium
The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q.
Key knowledge
The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q. At equilibrium it vanishes, giving ΔᵣG° = −RT ln K. The relation concerns thermodynamic direction and equilibrium, not reaction speed.
Values and equations
ΔᵣG = ΔᵣG° + RT ln Q; ΔᵣG° = −RT ln K
- ΔᵣG
- molar reaction Gibbs-energy change J mol⁻¹
- ΔᵣG°
- standard molar reaction Gibbs-energy change J mol⁻¹
- R
- molar gas constant J mol⁻¹ K⁻¹
- T
- absolute temperature K
- Q
- dimensionless reaction quotient 1
- K
- dimensionless equilibrium constant 1
Conditions and scope
- Use the same balanced reaction, temperature and standard states in ΔᵣG°, Q and K.
- The direction criterion assumes fixed temperature and pressure with the stated work constraints; concentrations alone may not equal activities.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inspected the nonstandard Gibbs-energy expression and its equilibrium specialization.
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Entry details
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- uni-chem-gibbs-equilibrium
- Revision
- core.1
- Structured reference record
- University core expansion