Le Chatelier's Principle Simulator
Le Chatelier's Principle: If a system at equilibrium is subjected to a change, the system will shift to partially oppose the change and restore a new equilibrium.
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = −92 kJ/mol
This is the Haber process — an exothermic, forward reaction that reduces the number of gas moles (4 → 2).
Apply a change:
↑ Increase temperatureAdd energy to the system
↓ Decrease temperatureRemove energy from the system
↑ Increase pressureCompress the gas mixture
↓ Decrease pressureExpand the gas mixture
+ Add more N₂Increase [N₂]
− Remove NH₃Decrease [NH₃]
⚡ Add catalystProvide alternative pathway
↻ ResetReturn to equilibrium
System at equilibrium. Choose a change above to see how the equilibrium shifts.
Equilibrium Constant (Kc)
For: aA + bB ⇌ cC + dD
Kc = [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ
Products over reactants, each raised to the power of their stoichiometric coefficient. Only changes with temperature — not concentration, pressure, or catalysts.
Kc is large (≫1)
Equilibrium lies to the right. Products are favoured. High yield of product at equilibrium.
Kc is small (≪1)
Equilibrium lies to the left. Reactants are favoured. Low yield of product at equilibrium.
Temperature increases
For exothermic: Kc decreases (shifts left).
For endothermic: Kc increases (shifts right).
Catalyst added
Kc is unchanged. Equilibrium is reached faster, but the position doesn't shift. Both forward and reverse rates increase equally.
Edexcel exam tip: Kc only changes with temperature. If asked "what happens to Kc when pressure increases?" the answer is NOTHING — Kc stays the same. The position of equilibrium shifts, but Kc is constant at constant temperature. This catches out many students.