Gibbs Free Energy Calculator
Calculate delta G = delta H - T * delta S. Determine reaction spontaneity.
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Enter the enthalpy change (delta H) in kJ/mol, the temperature in Kelvin, and the entropy change (delta S) in J/(mol K). The calculator computes delta G = delta H - T * delta S and indicates whether the reaction is spontaneous.
About the Gibbs Free Energy Calculator
Gibbs free energy determines whether a process is thermodynamically spontaneous. When delta G is negative, the process can occur without external energy. The equation delta G = delta H - T * delta S combines enthalpy (heat) and entropy (disorder) contributions. It is one of the most important equations in all of chemistry and biochemistry.
Frequently Asked Questions
What does a negative delta G mean?
A negative delta G means the reaction is spontaneous (thermodynamically favorable) under the given conditions. It will proceed without external energy input. Note that spontaneous does not mean fast.
Why is delta S entered in J/(mol K) but delta H in kJ/mol?
This matches how thermodynamic data is commonly tabulated. Entropy values are typically small numbers in J/(mol K), while enthalpy values are in kJ/mol. The calculator converts delta S to kJ/(mol K) internally.
At what temperature does a reaction become spontaneous?
Set delta G = 0 and solve: T = delta H / delta S. If both delta H and delta S are negative, the reaction is spontaneous below this temperature. If both are positive, it is spontaneous above this temperature.