The condition ΔG = 0 is very important because it defines chemical equilibrium. Here’s a simple explanation:
1. Meaning of ΔG = 0
- When ΔG = 0, the reaction is no longer spontaneous in either direction.
- The system has reached a point where the rate of the forward reaction equals the rate of the reverse reaction.
- No net change occurs in the concentrations of reactants and products.
2. Why it matters
- ΔG = 0 tells us the position of equilibrium.
- It helps chemists predict how much product or reactant will be present at equilibrium.
- It also shows that the system has minimized its free energy, which is a natural tendency.
3. Practical examples
- Water boiling at 100°C and 1 atm → ΔG = 0 for liquid-vapor transition → water and vapor coexist.
- N₂ + 3H₂ ⇌ 2NH₃ (Haber process) → at equilibrium ΔG = 0 → the amounts of N₂, H₂, and NH₃ remain constant.
Summary
- ΔG = 0 → reaction at equilibrium.
- No net change occurs, forward and reverse rates are equal.
- The system has reached its lowest free energy under the given conditions.