Gibbs Free Energy (ΔG) Calculator online tool
- Reaction-Based Mode: Input ΔG values of reactants and products.
- Formula-Based Mode: Use the equation ΔG = ΔH − TΔS by providing enthalpy, entropy, and temperature.
Dual-Mode ΔG Calculator
Reactants
Products
Gibbs Free Energy of Reaction (ΔGrxn)
The Ultimate Tool for Reaction Spontaneity
This advanced calculator determines the Gibbs Free Energy change (ΔG), the definitive value for predicting whether a chemical reaction will proceed spontaneously. It offers two powerful methods to suit your available data.
Method 1: By Formation (ΔG°f)
This method is ideal when you are working under standard conditions (298.15 K, 1 atm) and have access to tables of standard Gibbs free energies of formation (ΔG°f).
The formula is:
This approach calculates the overall ΔG° by subtracting the total free energy of the reactants from that of the products. Remember that ΔG°f for a pure element in its most stable form is 0.
Method 2: By Equation (ΔH, T, ΔS)
This is the fundamental thermodynamic equation. It's incredibly powerful because it allows you to calculate ΔG at any temperature, not just standard conditions. It reveals how temperature influences spontaneity.
The formula is:
Where:
- ΔH is the total change in enthalpy (heat).
- T is the absolute temperature in Kelvin.
- ΔS is the total change in entropy (disorder).
This tool automatically handles unit conversions (e.g., from °C to K, and J/K to kJ/K) to prevent common errors and ensure an accurate calculation.
How to Interpret the Result
The sign of ΔG is the key:
- ΔG < 0 (Negative): The reaction is spontaneous in the forward direction (exergonic).
- ΔG > 0 (Positive): The reaction is non-spontaneous (endergonic). Energy must be supplied for it to occur.
- ΔG = 0: The system is at equilibrium, with the forward and reverse reactions occurring at equal rates.