Le Chatelier’s Principle Simulator
Predict how an equilibrium shifts when concentration, temperature, pressure, inert gas, or catalyst conditions change. Use visible controls, quick examples, and supporting visuals to understand why the system shifts left, right, or not at all.
Background
Le Chatelier’s principle says a system at equilibrium responds to a stress by shifting in the direction that partially counteracts that stress. This simulator uses the balanced reaction, phase tags, reaction enthalpy, and gas mole counts to build a student-friendly prediction.
How to use this simulator
- Enter a balanced equilibrium equation and include phase tags such as (g), (aq), (s), or (l).
- Choose the stress card: concentration, temperature, pressure/volume, inert gas, or catalyst.
- Use the visible control buttons to increase/decrease temperature, increase/decrease pressure, or add/remove species.
- Review the visual shift, gas-mole summary, and reasoning steps.
How this simulator works
The simulator applies qualitative Le Chatelier logic. It does not calculate a new equilibrium concentration table. For pressure changes, it counts gas-phase coefficients from the equation. For temperature changes, it treats heat as a product for exothermic reactions and as a reactant for endothermic reactions.
Formulas & Rules Used
Gas mole difference: Δngas = Σνproducts,g − Σνreactants,g
Increase pressure: favors the side with fewer gas moles.
Decrease pressure: favors the side with more gas moles.
Exothermic temperature increase: shifts left because heat behaves like a product.
Endothermic temperature increase: shifts right because heat behaves like a reactant.
Example Problems & Step-by-Step Solutions
Example 1 — Pressure increase
N2(g) + 3 H2(g) ⇌ 2 NH3(g). Reactants have 4 gas moles and products have 2 gas moles. Increasing pressure favors fewer gas moles, so the equilibrium shifts right.
Example 2 — Temperature increase in an exothermic reaction
For an exothermic reaction, heat behaves like a product. Increasing temperature adds heat, so the system shifts left to consume some of the added heat.
Example 3 — Add product
If NH3 is added to N2(g) + 3 H2(g) ⇌ 2 NH3(g), product concentration increases. The system shifts left to consume the added product.
Frequently Asked Questions
Q: How do I control temperature and pressure?
Select the Temperature or Pressure / volume stress card, then use the visible increase/decrease buttons before clicking Predict Shift.
Q: Why do phase tags matter?
Pressure changes depend on gas moles, so the simulator needs (g) tags to know which species are gases.
Q: Does adding an inert gas change equilibrium?
At constant volume, usually no. At constant pressure, it can shift toward the side with more gas moles.
Q: Do catalysts shift equilibrium?
No. Catalysts speed up both directions and help equilibrium arrive faster, but they do not change the equilibrium position.
All calculators