AP Chemistry / Unit 7: Equilibrium
7.9 Introduction to Le Châtelier's Principle
Notes
A system at equilibrium shifts to reduce a stress:
- Add reactant → shift right. Remove product → shift right.
- Increase pressure (decrease volume) → shift toward fewer gas moles.
- Raise temperature → shift in the endothermic direction.
Practice
$N_2+3H_2\rightleftharpoons2NH_3$. Decreasing the volume shifts:
Fewer gas moles on the right (2 vs 4).
For an exothermic reaction, raising the temperature shifts:
Heat acts like a product.
Adding more reactant shifts equilibrium:
Uses up the added reactant.
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