Gibbs Free Energy Calculator
Calculate Gibbs free energy, enthalpy, entropy, or temperature and determine reaction spontaneity
Calculate Gibbs Free Energy Properties
Heat absorbed or released in the reaction
Change in disorder of the system
Absolute temperature of the reaction
Quick Load Example Reactions
Gibbs Free Energy Results
Formula used: ΔG = ΔH - T × ΔS
Analysis:
Energy Analysis: Both enthalpy and entropy contribute significantly
Example Calculation
Haber Process: N₂ + 3H₂ → 2NH₃
Given: ΔH = -92.22 kJ, ΔS = -198.75 J/K, T = 20°C (293.15 K)
Question: Is the reaction spontaneous at room temperature?
Solution
1. ΔG = ΔH - T × ΔS
2. ΔG = -92.22 kJ - (293.15 K × -0.19875 kJ/K)
3. ΔG = -92.22 kJ + 58.26 kJ
4. ΔG = -33.96 kJ
Conclusion: Since ΔG < 0, the reaction is spontaneous at 20°C
Spontaneity Guide
ΔG < 0
Spontaneous (Exergonic)
Reaction proceeds without external energy
ΔG > 0
Non-spontaneous (Endergonic)
Requires external energy input
ΔG = 0
At Equilibrium
No net change in the system
Temperature Effects
Understanding Gibbs Free Energy
What is Gibbs Free Energy?
Gibbs free energy (G) is a thermodynamic potential that measures the maximum reversible work that can be performed by a system at constant temperature and pressure. It combines the effects of enthalpy and entropy to predict reaction spontaneity.
Key Concepts
- •Negative ΔG indicates a spontaneous process
- •Positive ΔG requires external energy input
- •ΔG = 0 represents equilibrium conditions
- •Temperature affects the entropy contribution
The Gibbs Equation
Primary Formula
ΔG = ΔH - TΔS
ΔG = Gibbs free energy change
ΔH = Enthalpy change
T = Absolute temperature (K)
ΔS = Entropy change
Equilibrium Relationship
ΔG = -RT ln(K)
Relates free energy to equilibrium constant
Standard Conditions
ΔG° measured at 25°C, 1 atm, 1 M concentrations
Enthalpy vs Entropy Contributions
Enthalpy-Driven Reactions
When |ΔH| >> |TΔS|, the reaction is primarily driven by enthalpy changes.
Examples: Combustion reactions, acid-base neutralizations
Entropy-Driven Reactions
When |TΔS| >> |ΔH|, the reaction is primarily driven by entropy changes.
Examples: Dissolution processes, phase transitions