Relationship between Gibbs Free Energy and Equilibrium Constant Calculator

Formula first

Overview

The equation shows that the spontaneity of a reaction under standard conditions is directly related to the position of its equilibrium. A negative Gibbs free energy value results in an equilibrium constant greater than one, indicating that the products are favored at equilibrium. Conversely, a positive Gibbs free energy value implies that the reactants are favored.

Symbols

Variables

$\Delta$ G^$\circ$ = Standard Gibbs Free Energy change (J/mol), R = Gas Constant (J/mol·K), T = Temperature (K), K = Equilibrium Constant

Apply it well

When To Use

When to use: Use this equation when you need to calculate the equilibrium constant from standard thermodynamic data or vice versa.

Why it matters: It allows chemists to predict the extent of a chemical reaction without having to measure concentrations experimentally at equilibrium.

Avoid these traps

Common Mistakes

• Forgetting to convert kiloJoules (kJ) to Joules (J) when performing calculations.
• Using the wrong temperature units (Celsius instead of Kelvin).
• Confusing the standard Gibbs free energy (ΔG°) with non-standard Gibbs free energy (ΔG).

One free problem

Practice Problem

Calculate the equilibrium constant K for a reaction at 298 K where ΔG° = -5.70 kJ/mol. (R = 8.314 J/mol·K)

Solve for: $K$

Hint: Rearrange to K = e^(-ΔG / RT). Ensure ΔG is in Joules.

The full worked solution stays in the interactive walkthrough.

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Related Formulas

References

Sources

1. Atkins, P., & de Paula, J. (2014). Physical Chemistry (10th ed.). Oxford University Press.
2. Zumdahl, S. S., & Zumdahl, S. A. (2017). Chemistry (10th ed.). Cengage Learning.
3. Atkins, P., & de Paula, J. (2014). Physical Chemistry, 10th Edition.
4. Royal Society of Chemistry, A-Level Chemistry Resources.
5. A-Level Chemistry (OCR/AQA/Edexcel Specification - Thermodynamics section)