Gibbs Free Energy Calculator
Says whether a reaction is thermodynamically feasible at a given temperature.
Gibbs free energy change ΔG
— kJ/mol
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
At this temperature —
Equilibrium constant K —
Temperature where ΔG = 0 —
Reading this —
The formula
ΔG = ΔH − T × ΔS K = e^(−ΔG ÷ RT)
T must be in kelvin. The sign of ΔG can flip as temperature rises because the T × ΔS term grows with it. R is 8.314 J/(mol·K).
What to watch out for
The default values are close to the decomposition of calcium carbonate: not feasible at room temperature, but feasible once hot enough.
Frequently Asked Questions
What is ΔG for ΔH = 178 kJ/mol and ΔS = 161 J/(mol·K) at 25 °C?
130.0 kJ/mol, which is not feasible.
Why is the temperature in kelvin?
The equation needs absolute temperature. Using Celsius would give the wrong answer, and the wrong sign at some temperatures.