Gibbs Free Energy
Predict reaction spontaneity (ΔG = ΔH - TΔS)
✅ What This Calculator Is & Why It Matters
The Gibbs Free Energy (ΔG) Calculator determines the ultimate thermodynamic fate of a chemical reaction. It tells you whether a reaction will happen spontaneously on its own, or if you must constantly force it to happen by adding external energy.
Why does it matter? It is the master equation of thermodynamics. A reaction might release massive amounts of heat (favorable Enthalpy) but result in a highly ordered structure (unfavorable Entropy). Gibbs Free Energy balances these two competing forces to give you a definitive "Yes" or "No" on whether the reaction is thermodynamically possible.
✅ The Formula Explained Simply
The equation balances heat (Enthalpy, ΔH) against disorder (Entropy, ΔS) at a specific Temperature (T):
ΔG = ΔH - TΔS
If ΔG is negative (< 0), the reaction is spontaneous. If ΔG is positive (> 0), it is non-spontaneous.
✅ 3-5 Real-World Examples
Example 1: Spontaneous Reaction (Negative ΔG)
Iron rusting. It releases heat (ΔH < 0) and creates disorder (ΔS > 0).
Result: ΔG is negative at all temperatures. Rusting is always spontaneous (even if it is slow).
Example 2: Temperature Dependent
Melting ice. It requires heat (ΔH > 0) but creates disorder (ΔS > 0).
Result: At -10°C, ΔG is positive (ice stays frozen). At +10°C, the TΔS term overwhelms the heat requirement, ΔG becomes negative, and the ice spontaneously melts.
✅ FAQ Section (Google PAA Targeted)
If ΔG is negative, why isn't the reaction happening right now?
Gibbs Free Energy says absolutely nothing about *speed* (kinetics), only about *possibility* (thermodynamics). Diamonds turning into graphite has a negative ΔG (it is spontaneous), but it takes millions of years because the activation energy is so high.
What does it mean if ΔG is exactly zero?
It means the system is at perfect dynamic equilibrium. The forward and reverse reactions are happening at the exact same rate. Phase changes (like water boiling at exactly 100°C) have a ΔG of zero.
✅ Pro-Tips for Gibbs Math
- The Units Trap: Enthalpy (ΔH) is almost always given in kiloJoules (kJ), while Entropy (ΔS) is given in Joules (J). You MUST divide ΔS by 1000 to convert it to kJ before subtracting it from ΔH, or your answer will be wildly incorrect.
✅ Related Calculators
✅ AI Explanation of Results
Our AI explicitly interprets the sign of your calculated ΔG, stating clearly whether the reaction is exergonic (spontaneous) or endergonic (non-spontaneous) at your specified temperature.
About the Gibbs Free Energy Calculator
Solve chemical kinetics and thermodynamics problems. Calculate Gibbs free energy, activation energy, entropy, or reaction rates.
This precision chemistry tool is designed for academic reference, laboratory workflows, and student education. It provides instant, real-time computational results with standard formulas and dimensional analysis inputs.