key term - Le Chatelier's Principle

Definition

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change and re-establish equilibrium. This principle is crucial for understanding how changes in concentration, temperature, and pressure affect chemical systems and their equilibria.

5 Must Know Facts For Your Next Test

1. Le Chatelier's Principle explains how adding or removing reactants or products can shift the equilibrium position in a reversible reaction.
2. When the temperature of an exothermic reaction is increased, the equilibrium shifts to favor the endothermic direction, reducing the formation of products.
3. Increasing pressure on a gaseous equilibrium favors the side with fewer moles of gas, while decreasing pressure favors the side with more moles.
4. In precipitation reactions, adding a common ion decreases solubility and shifts the equilibrium toward forming more solid precipitate.
5. Changes in temperature affect equilibrium constants; an increase in temperature for an endothermic reaction increases K, while it decreases for an exothermic reaction.

Review Questions

• How does Le Chatelier's Principle apply to changes in concentration in a chemical equilibrium?
  • According to Le Chatelier's Principle, if you add more reactant or product to a system at equilibrium, the system will shift in a direction that reduces the effect of that change. For instance, adding more reactant will drive the reaction towards producing more product until a new equilibrium is established. Conversely, removing product will shift the equilibrium toward producing more product as well.
• Explain how temperature changes impact the position of equilibrium according to Le Chatelier's Principle.
  • Temperature changes can significantly affect equilibrium positions. For an exothermic reaction, increasing temperature shifts the equilibrium towards reactants, as the system tries to absorb this added heat. Conversely, lowering the temperature shifts it toward products, allowing for heat release. This adjustment helps re-establish balance within the chemical system.
• Evaluate how Le Chatelier's Principle can be used to predict outcomes in real-world applications such as industrial processes.
  • In industrial applications, understanding Le Chatelier's Principle allows chemists and engineers to optimize reactions for maximum yield. By manipulating concentration, temperature, and pressure based on this principle, one can enhance product formation. For example, in the Haber process for ammonia synthesis, increasing pressure favors production due to fewer moles of gas on that side, leading to higher efficiency and profitability in ammonia production.

Related terms

Dynamic Equilibrium:

A state in which the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in concentration of reactants and products.

Equilibrium Constant (K): A numerical value that expresses the ratio of concentrations of products to reactants at equilibrium for a given reaction at a specific temperature.

Common Ion Effect: The decrease in solubility of a salt when a common ion is added to the solution, demonstrating the principle of Le Chatelier's by shifting the equilibrium position.