Gibbs free energy (ΔG) is a thermodynamic quantity that predicts whether a chemical reaction or process will be spontaneous at constant temperature and pressure.
Key points:
- Definition:
- It combines the effects of enthalpy (ΔH) and entropy (ΔS) into a single value.
- It tells us whether a reaction can occur naturally without outside energy.
- Interpretation of ΔG:
- ΔG < 0 → The reaction is spontaneous (can occur on its own).
- ΔG > 0 → The reaction is non-spontaneous (requires energy input).
- ΔG = 0 → The system is at equilibrium; no net change occurs.
- Factors affecting ΔG:
- Enthalpy (ΔH): Heat released or absorbed by the reaction.
- Entropy (ΔS): Change in disorder of the system.
- Temperature (T): Affects the influence of entropy on spontaneity.
Simple analogy:
- Think of ΔG as the “energy available to do work.” If ΔG is negative, the system has energy available to drive the process forward spontaneously.