Gibbs Free Energy Calculator
Calculate ΔG
ΔG = ΔH - TΔS
Equilibrium Temperature
Find T where ΔG = 0 (ΔH = TΔS)
ΔG° from Equilibrium Constant
ΔG° = -RT·ln(K)
Non-Standard ΔG
ΔG = ΔG° + RT·ln(Q)
Formula
ΔG = ΔH - TΔS | ΔG° = -RT·ln(K) | ΔG = ΔG° + RT·ln(Q) | T_eq = ΔH/ΔS
Frequently Asked Questions
What is Gibbs free energy?
Gibbs free energy (G) combines enthalpy and entropy to predict spontaneity: ΔG = ΔH - TΔS. If ΔG < 0, the reaction is spontaneous. If ΔG > 0, it is non-spontaneous. If ΔG = 0, the system is at equilibrium.
How are ΔG and K related?
ΔG° = -RT·ln(K). When K > 1, ΔG° < 0 (products favored). When K < 1, ΔG° > 0 (reactants favored). Under non-standard conditions: ΔG = ΔG° + RT·ln(Q).
When is a reaction always spontaneous?
When ΔH < 0 and ΔS > 0 (exothermic with entropy increase), ΔG is always negative. When ΔH > 0 and ΔS < 0, ΔG is always positive (never spontaneous). Other combinations depend on temperature.
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