Equilibrium Constant

Definition

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to the concentrations of reactants at equilibrium for a given chemical reaction. It provides insight into the extent of a reaction and indicates whether the reactants or products are favored in a particular equilibrium state. This constant is crucial for understanding how changes in conditions affect the position of equilibrium and the overall energy dynamics of chemical reactions.

5 Must Know Facts For Your Next Test

1. The value of the equilibrium constant is temperature-dependent, meaning it can change with fluctuations in temperature for a given reaction.
2. If K > 1, products are favored at equilibrium, while K < 1 indicates that reactants are favored.
3. The equilibrium constant expression is derived from the balanced chemical equation, with each concentration raised to the power of its stoichiometric coefficient.
4. When calculating K for reactions involving solids or liquids, their concentrations are not included in the expression since they remain constant.
5. Equilibrium constants can be used to predict the direction of a reaction when the initial concentrations of reactants and products are known.

Review Questions

• How does Le Chatelier's Principle relate to changes in the equilibrium constant when external conditions are altered?
  • Le Chatelier's Principle states that if a system at equilibrium experiences a change in concentration, temperature, or pressure, the system will respond by shifting its equilibrium position to counteract that change. While the equilibrium constant itself remains unchanged unless temperature is altered, the position of equilibrium can shift to favor either products or reactants depending on the nature of the change. This dynamic adjustment reflects how systems strive to maintain balance amidst disturbances.
• Describe how Gibbs Free Energy and the equilibrium constant are interconnected when assessing chemical reactions.
  • Gibbs Free Energy ( ext{ΔG}) and the equilibrium constant (K) are closely linked through the relationship ext{ΔG°} = -RT ext{ln}(K), where R is the gas constant and T is temperature in Kelvin. When K is greater than 1, it indicates that products are favored, leading to a negative ext{ΔG°}, suggesting that the reaction is spontaneous. Conversely, if K is less than 1, ext{ΔG°} is positive, indicating non-spontaneity and favoring reactants. This connection provides insight into both thermodynamics and reaction tendencies.
• Evaluate how changes in temperature affect both K and the direction of a chemical reaction at equilibrium.
  • Changes in temperature can significantly influence both the value of the equilibrium constant (K) and the direction in which a reaction shifts. For endothermic reactions, increasing temperature raises K, favoring product formation; conversely, for exothermic reactions, raising temperature decreases K, shifting towards reactants. This effect illustrates how thermodynamic principles dictate not just whether a reaction will occur but also its extent under different thermal conditions. Understanding this relationship helps predict outcomes in various chemical processes.

Related terms

Le Chatelier's Principle:

A principle that states if an external change is applied to a system at equilibrium, the system will adjust itself to counteract that change and restore a new equilibrium.

Gibbs Free Energy:

A thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure, which helps determine the spontaneity of reactions.

Reaction Quotient: A ratio similar to the equilibrium constant that measures the concentrations of reactants and products at any point in a reaction, not necessarily at equilibrium.