What Is the Gibbs Free Energy & Spontaneity Calculator?
Gibbs Free Energy is the maximum amount of non-expansion work extractable from a closed thermodynamic system at constant temperature and pressure.
How Does the Gibbs Free Energy & Spontaneity Calculator Work?
A reaction is thermodynamically spontaneous when ΔG is negative. When ΔG is zero, the system has reached dynamic chemical equilibrium.
Gibbs Free Energy & Spontaneity Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Gibbs energy change ΔG equals enthalpy change ΔH minus absolute temperature T in Kelvin times entropy change ΔS.
How to Use the Gibbs Free Energy & Spontaneity Calculator
- Input the enthalpy change ΔH in kJ/mol.
- Input the entropy change ΔS in J/(mol·K).
- Specify the temperature in °C.
Step-by-Step Example Calculation
Haber-Bosch Ammonia Synthesis (25°C)
Input Values:
Understanding Your Result
Gibbs Free Energy (ΔG): In kJ/mol. Negative indicates spontaneous forward process.
Spontaneity Status: Exergonic, endergonic, or equilibrium.
Crossover Temperature: The exact temperature where ΔG switches sign.
Factors That Affect the Result
- Enthalpy drives low-temperature behavior; entropy term (T·ΔS) dominates high-temperature behavior.
When Should You Use This Calculator?
- Chemical reactor design, biochemical metabolic pathway coupling, metallurgy, and material synthesis.
Assumptions & Limitations
- Assumes constant pressure and temperature. Assumes ΔH and ΔS are approximately temperature-independent over the evaluated range.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard Gibbs-Helmholtz thermodynamic formulation.