Gibbs Free Energy (G) measures the maximum usable energy in a system available to do work at constant temperature and pressure.
Gibbs Free Energy helps us predict whether a chemical reaction will occur spontaneously without outside energy input.
A reaction is spontaneous if: ΔG<0 Negative ΔG = spontaneous reaction Positive ΔG = non-spontaneous reaction ΔG = 0 = equilibrium
ΔH < 0: Exothermic reaction (releases heat) ΔH > 0: Endothermic reaction (absorbs heat) This affects ΔG directly.
ΔS > 0: More disorder (favorable) ΔS < 0: Less disorder (unfavorable) Entropy changes also impact ΔG.
Temperature (T) can shift the balance: High T favors reactions increasing disorder (entropy-driven). Low T favors reactions releasing energy (enthalpy-driven).
Combustion reactions have: ΔH < 0 (release heat) ΔS > 0 (increase disorder) Result: Always spontaneous (ΔG < 0).
At room temperature: ΔH > 0 (absorbs heat) ΔS > 0 (increases disorder) Result: ΔG < 0, spontaneous at high temperatures.
ΔH > 0 (energy absorbed) ΔS < 0 (more ordered products) Result: Non-spontaneous without sunlight (positive ΔG).
Gibbs Free Energy guides processes like: Designing batteries Understanding metabolism Developing sustainable energy sources
Non-spontaneous reactions can occur by coupling with spontaneous ones. Example: ATP hydrolysis powers biological processes.
Gibbs Free Energy predicts reaction spontaneity. Negative ΔG = spontaneous. Factors: Enthalpy, entropy, and temperature.