Equilibrium Constant

Definition

The equilibrium constant, often denoted as K, is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a reversible chemical reaction. It is a fundamental concept that links thermodynamics to chemical kinetics, indicating the extent to which a reaction favors the formation of products or reactants. A large equilibrium constant suggests that products are favored, while a small constant indicates that reactants are favored.

5 Must Know Facts For Your Next Test

1. The value of the equilibrium constant is temperature-dependent and will change if the temperature of the system changes.
2. For reactions involving gases, the equilibrium constant can be expressed in terms of partial pressures, known as Kp, or concentrations, known as Kc.
3. If K > 1, the products are favored at equilibrium; if K < 1, the reactants are favored.
4. The equilibrium constant expression does not include solids or liquids because their concentrations do not change during the reaction.
5. For a given reaction, reversing the direction of the reaction will result in the reciprocal of the original equilibrium constant.

Review Questions

• How does the value of the equilibrium constant relate to the direction in which a chemical reaction will proceed?
  • The value of the equilibrium constant provides insight into which side of a reversible reaction is favored. If K is greater than 1, it indicates that at equilibrium, there are more products than reactants, meaning the reaction proceeds favorably towards products. Conversely, if K is less than 1, it shows that reactants are favored at equilibrium, suggesting that the reaction does not proceed significantly towards forming products.
• In what ways do changes in temperature affect the equilibrium constant and what implications does this have for predicting chemical behavior?
  • Changes in temperature can significantly impact the equilibrium constant. For endothermic reactions, increasing temperature typically raises K, favoring product formation. For exothermic reactions, increasing temperature usually lowers K, shifting favor toward reactants. Understanding this temperature dependence is crucial for predicting how a system will respond to thermal changes and for optimizing reactions in industrial applications.
• Evaluate how Le Chatelier's Principle and the concept of equilibrium constant interact in a dynamic chemical system.
  • Le Chatelier's Principle provides a framework for understanding how a dynamic chemical system responds to external changes while maintaining equilibrium. When stressors like concentration or pressure changes are applied, the system shifts in response to counteract those changes. The equilibrium constant quantifies this shift by defining ratios of product and reactant concentrations at equilibrium. Thus, knowing both principles helps predict how a system will achieve new equilibria after disturbances, enhancing our grasp of chemical reactivity and stability.

Related terms

Le Chatelier's Principle: A principle stating that if an external change is applied to a system at equilibrium, the system will adjust to counteract that change and restore a new equilibrium.

Gibbs Free Energy: A thermodynamic potential that measures the maximum reversible work obtainable from a system at constant temperature and pressure, used to predict the direction of a reaction.

Reaction Quotient: A measure of the relative amounts of products and reactants present during a reaction at any point in time, which can be compared to the equilibrium constant to determine the direction of the reaction.