How to use the gibbs free energy calculator
Find spontaneity from enthalpy, entropy and temperature. Enter enthalpy change δh, entropy change δs, temperature in the fields above; the gibbs energy δg, spontaneous?, crossover temperature are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- H — Enthalpy change ΔH (kJ/mol)
- S — Entropy change ΔS (J/(mol·K))
- T — Temperature (K)
Worked example
With enthalpy change δh = -92 kJ/mol, entropy change δs = -199 J/(mol·K), temperature = 298 K, the calculator gives gibbs energy δg ≈ -32.698 kJ/mol; spontaneous? ≈ Yes; crossover temperature ≈ 462.3116 K.
Frequently asked questions
What is the formula for the gibbs free energy calculation?
Gibbs energy ΔG (kJ/mol) = H-T × S / 1000. Spontaneous? = [Gibbs energy ΔG]<0?"Yes":"No". Crossover temperature (K) = H × 1000 / S. Here H is enthalpy change δh (kJ/mol), S is entropy change δs (J/(mol·K)), T is temperature (K).
What inputs do I need for the gibbs free energy calculator?
You need enthalpy change δh in kJ/mol, entropy change δs in J/(mol·K), temperature in K. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.