Chemical reaction equilibrium

Definition

Chemical reaction equilibrium is a state in a chemical reaction where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time. This balance indicates that the system has reached a dynamic stability, where changes in conditions may shift the position of equilibrium but do not affect the overall existence of the equilibrium state.

5 Must Know Facts For Your Next Test

1. At chemical reaction equilibrium, the concentrations of reactants and products remain constant but not necessarily equal.
2. The equilibrium constant (K) provides insight into the extent of a reaction; a large K indicates products are favored, while a small K indicates reactants are favored.
3. Temperature changes can affect the position of equilibrium; exothermic reactions shift left with increased temperature, while endothermic reactions shift right.
4. Catalysts do not change the position of equilibrium; they only speed up the rate at which equilibrium is reached.
5. In non-ideal solutions, factors like interactions between molecules can affect how equilibria are established compared to ideal solutions.

Review Questions

• How does Le Chatelier's Principle apply to changes in concentration or pressure during a chemical reaction at equilibrium?
  • Le Chatelier's Principle states that if an external change, such as concentration or pressure, is applied to a system at equilibrium, the system will adjust itself to counteract that change. For example, if the concentration of reactants increases, the system will shift towards producing more products to re-establish equilibrium. Similarly, if pressure is increased in a gaseous reaction, the system may shift toward the side with fewer moles of gas to reduce pressure.
• Discuss how temperature affects the position of chemical reaction equilibrium in exothermic and endothermic reactions.
  • Temperature changes impact the position of equilibrium based on whether a reaction is exothermic or endothermic. In an exothermic reaction, heat can be considered a product; increasing temperature shifts the equilibrium towards the reactants to absorb excess heat. Conversely, for an endothermic reaction where heat is a reactant, raising the temperature shifts equilibrium towards products. This demonstrates how dynamic equilibria respond to thermal changes.
• Evaluate the implications of using catalysts on chemical reaction equilibria and the overall rate of reactions.
  • Using catalysts in chemical reactions accelerates both forward and reverse reactions equally without altering the position of equilibrium. This means that while catalysts speed up the time it takes to reach equilibrium, they do not favor either side of the reaction; thus, the concentrations of reactants and products at equilibrium remain unchanged. This distinction is crucial because it highlights how catalysts enhance efficiency without impacting thermodynamic favorability.

Related terms

Le Chatelier's Principle: A principle that states if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.

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.

Reaction Quotient (Q): A ratio similar to the equilibrium constant but calculated using the concentrations of reactants and products at any point in time, not just at equilibrium.