Standard Gibbs free energy Calculator

Formula first

Overview

This fundamental thermodynamic equation relates the standard Gibbs free energy change (ΔG°) to the equilibrium constant (K) of a chemical reaction. It provides a bridge between energetics and the final ratio of products to reactants at a specific temperature.

Symbols

Variables

R = Gas Constant, T = Temperature, K = Equilibrium Constant, $\Delta$ G^$\circ$ = Standard Gibbs Energy

Apply it well

When To Use

When to use: Apply this equation when calculating the extent of a reaction at equilibrium or finding the spontaneity of a process under standard conditions. It is specifically for systems at a constant temperature where standard state values (1 atm or 1 M) are provided.

Why it matters: It allows scientists to predict how temperature changes will shift equilibrium positions in industrial synthesis, like the Haber process. It also helps biochemists understand the energetics of enzyme-catalyzed reactions in the human body.

Avoid these traps

Common Mistakes

• Using log10 instead of ln.
• Forgetting the negative sign.

One free problem

Practice Problem

Calculate the standard Gibbs free energy change (ΔG°) for a reaction at 298.15 K that has an equilibrium constant (K) of 2.0 × 10⁴.

Solve for: $G0$

Hint: Use the natural logarithm (ln) of the equilibrium constant and ensure the result is in Joules per mole.

The full worked solution stays in the interactive walkthrough.

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Related Formulas

References

Sources

1. Atkins' Physical Chemistry
2. Callen, H. B. (1985). Thermodynamics and an Introduction to Thermostatistics.
3. Wikipedia: Gibbs free energy
4. Wikipedia: Equilibrium constant
5. NIST CODATA
6. IUPAC Gold Book
7. Atkins, P. W.; de Paula, J. Atkins' Physical Chemistry. 11th ed. Oxford University Press, 2018.
8. Callen, H. B. Thermodynamics and an Introduction to Thermostatistics. 2nd ed. John Wiley & Sons, 1985.