Here’s a explanation of how Gibbs free energy (ΔG) is calculated for a reaction without using equations:
1. Using standard free energy values
- Every substance has a standard free energy of formation, which is like a “baseline energy” for 1 mole of that substance under standard conditions.
- To find ΔG for a reaction:
- Compare the total free energy of the products with the total free energy of the reactants.
- Subtract the reactants’ total from the products’ total.
- If ΔG is negative, the reaction is spontaneous.
- If ΔG is positive, the reaction is non-spontaneous.
2. Using equilibrium constant
- The equilibrium constant (K) tells us how far a reaction goes at equilibrium.
- ΔG is related to K:
- Large K (products favored) → ΔG is negative → reaction is spontaneous.
- Small K (reactants favored) → ΔG is positive → reaction is not spontaneous.
3. Adjusting for conditions
- The standard free energy assumes standard conditions (1 atm, 25°C, 1 M solutions).
- If conditions differ (like concentration, temperature, or pressure), ΔG can be adjusted to account for those changes.
Summary
- ΔG tells us whether a reaction will happen naturally.
- Compare the energy of products and reactants or use the equilibrium constant.
- Adjust for actual conditions if needed.