Gibbs Free Energy (ΔG = ΔH − TΔS) & Equilibrium Constant (K_eq) Calculator

Determine reaction spontaneity (ΔG° < 0) and log₁₀(K_eq) at any Kelvin temperature.

Gibbs Free Energy Change (ΔG°)
-12.2 kJ/mol
Entropic Term (−TΔS) 32.8 kJ/mol
log₁₀ Equilibrium Constant (log K) 2.14 log K
Crossover Temperature (T = ΔH/ΔS) 409.09 K
Inputs
kJ/mol
Standard enthalpy change ΔH° in kJ/mol.
J/(mol·K)
Standard entropy change ΔS° in J/(mol·K).
K
Reaction temperature in Kelvin (298.15 K = 25°C).
Results & Graph
Gibbs Free Energy Change (ΔG°)
-12.2 kJ/mol
Entropic Term (−TΔS)
32.8 kJ/mol
log₁₀ Equilibrium Constant (log K)
2.14 log K
Crossover Temperature (T = ΔH/ΔS)
409.09 K

Gibbs Free Energy Change (ΔG°)

Graph 1 • Enthalpy Kj Mol Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
-34.7 kJ/mol -11.8 kJ/mol 11.1 kJ/mol 50%: 10.3 kJ/mol 10.3 50% 75%: -0.95 kJ/mol -0.9 75% 100%: -12.2 kJ/mol -12.2 100% 125%: -23.45 kJ/mol -23.4 125% 150%: -34.7 kJ/mol -34.7 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Gibbs Free Energy Change (ΔG°) -12.2 kJ/mol Entropic Term (−TΔS) 32.8 kJ/mol log₁₀ Equilibrium Constant (log K) 2.14 log K Crossover Temperature (T = ΔH/ΔS) 409.09 K
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Gibbs Free Energy Change (ΔG°)-12.2 kJ/molEntropic Term (−TΔS)32.8 kJ/mollog₁₀ Equilibrium Constant (log K)2.14 log KCrossover Temperature (T = ΔH/ΔS)409.09 K
Summary: At 298.15 K, ΔG° = -12.2 kJ/mol (Exergonic / Spontaneous) with log₁₀(K_eq) = 2.14.
Summary: At 298.15 K, ΔG° = -12.2 kJ/mol (Exergonic / Spontaneous) with log₁₀(K_eq) = 2.14.
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Formula & Mathematical Methodology: Gibbs Free Energy & K_eq Reference Equation

ΔG° = ΔH° − T × (ΔS° / 1000)
ln(Keq) = −ΔG° × 1000R × T
ΔG° = ΔH° − T × (ΔS° / 1000); ln(K_eq) = −(ΔG° × 1000) / (R × T)
  • enthalpyKjMol: Enthalpy Kj Mol (kJ/mol)
  • entropyJmolK: Entropy Jmol K (J/(mol·K))
  • temperatureKelvin: Temperature Kelvin (K)

Rounding: Laboratory and clinical equations retain full floating-point precision and round displayed results to 2 decimal places.

Worked Example: Reference Calculation: Gibbs Free Energy & K_eq

Determine reaction spontaneity (ΔG° < 0) and log₁₀(K_eq) at any Kelvin temperature.

  1. Enter the reagent concentrations, assay readings, or clinical laboratory parameters.
  2. Compute the standard formula: ΔG° = ΔH° − T × (ΔS° / 1000); ln(K_eq) = −(ΔG° × 1000) / (R × T).
  3. Review the primary result, supporting reference intervals, and 3 SVG visualizations.
Result: Evaluates Gibbs Free Energy & K_eq via ΔG° = ΔH° − T × (ΔS° / 1000); ln(K_eq) = −(ΔG° × 1000) / (R × T).

Frequently Asked Questions

What formula is used by the Gibbs Free Energy (ΔG = ΔH − TΔS) & Equilibrium Constant (K_eq) Calculator?

It computes ΔG° = ΔH° − T × (ΔS° / 1000); ln(K_eq) = −(ΔG° × 1000) / (R × T) and plots three custom SVG graphs showing parameter sensitivity and component breakdowns.

Can I compare different reagent dilutions or lab scenarios side by side?

Yes. Use the "Compare (0/3)" button to pin up to 3 scenarios side by side.

Are entered values stored on any server?

No. Every calculation runs 100% locally in your browser.

Science & Engineering · Analytical Chemistry & Lab Bench

Gibbs Free Energy (ΔG = ΔH − TΔS) & Equilibrium Constant (K_eq) Calculator: inputs, method, and how to read the result

Determine reaction spontaneity (ΔG° < 0) and log₁₀(K_eq) at any Kelvin temperature.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Enthalpy Kj Mol: Standard enthalpy change ΔH° in kJ/mol.
  • Entropy Jmol K: Standard entropy change ΔS° in J/(mol·K).
  • Temperature Kelvin: Reaction temperature in Kelvin (298.15 K = 25°C).

What the calculation includes

With the default values shown, Gibbs Free Energy Change (ΔG°) is -12.2 kJ/mol. The calculation follows Gibbs Free Energy & K_eq Reference Equation; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Enthalpy Kj Mol from -45 kJ/mol to -40 kJ/mol changes Gibbs Free Energy Change (ΔG°) from -12.2 kJ/mol to -7.2 kJ/mol. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard IUPAC atomic weights, 25°C (298.15 K) reference thermodynamics, and published clinical literature equations.
  • Educational and laboratory reference tool only; clinical scoring calculators do not replace professional medical judgment or institutional protocols.

Scope: IUPAC / NIH Laboratory & Clinical Reference Standard Check the assumptions and limitations against your situation before relying on the estimate.

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