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chemistry/lechatelier
View PricingLe Châtelier's Principle: The Piston Chamber
Explore why adding inert gas shifts equilibrium under constant pressure but not constant volume.
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Key Concepts
Partial Pressure
The pressure contribution of each gas in a mixture. Partial pressure = (mole fraction) × (total pressure).
Le Châtelier's Principle
When a system at equilibrium is disturbed, it shifts to counteract the change.
Constant Volume vs Constant Pressure
Adding inert gas at constant volume doesn't change partial pressures; at constant pressure, volume expands.
Understanding Le Châtelier's Principle
**Le Châtelier's Principle** is a fundamental rule in chemistry stating that if a dynamic equilibrium is disturbed by changing the conditions, the system will shift its equilibrium position to counteract the applied change.
Key disturbance factors include changes in **concentration**, **temperature**, and **total pressure**. In gas-phase systems, shifts are dictated by the relative moles of gas on each side of the reaction and the resulting changes in **partial pressures**.
Through our piston chamber visualization, you can investigate the critical distinction between adding inert gas at **constant volume** (where no shift occurs) versus **constant pressure** (where a shift occurs toward the side with more moles of gas).
Equilibrium Shifts Summary
| Disturbance Factor | Change Applied | Equilibrium Shift Direction |
|---|---|---|
| Concentration | Increase Reactant / Decrease Product | Shift AWAY from added species |
| Decrease Reactant / Increase Product | Shift TOWARDS removed species | |
| Pressure (via Volume) | Increase Pressure (Decrease Volume) | Shift to FEWER moles of gas |
| Decrease Pressure (Increase Volume) | Shift to MORE moles of gas | |
| Temperature | Increase Temperature (Heat is added) | Shift Endothermic (+ΔH direction) |
| Decrease Temperature (Heat is removed) | Shift Exothermic (-ΔH direction) |
Frequently Asked Questions
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