Le Chatelier's Principle: Effect of Concentration
If you disturb a system at equilibrium, what does it do? According to Le Chatelier's Principle, the system will always try to fight back! It will shift in a direction that nullifies or reduces the effect of your disturbance.
1. The Core Statement
Le Chatelier's Principle: "If a system at equilibrium is subjected to an external change in concentration, pressure, or temperature, the equilibrium will shift in the direction that tends to counteract (or undo) that change."
2. Effect of Changing Concentration
Consider the reaction: Reactants ⇌ Products
- Adding Reactant (or Removing Product): The system has "too much" reactant. To fix this, it consumes the reactant to make more product. Shift: FORWARD.
- Adding Product (or Removing Reactant): The system has "too much" product. It consumes the excess product to turn it back into reactant. Shift: BACKWARD.
Practice Question
Q: In the Haber process (N2 + 3H2 ⇌ 2NH3), how can you use concentration changes to maximize the yield of Ammonia?
Answer: Continuously add N2 and H2 gases, OR continuously remove/liquefy the NH3 gas as it forms. Both actions will force the system to constantly shift in the forward direction!
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