Representations of Equilibrium

Representations of Equilibrium

Understanding Chemical Equilibrium

  • Chemical equilibrium is a state in a reversible reaction where the forward and reverse reactions occur at the same rate.
  • The equilibrium symbol used in chemical equations is a double half arrow showing the bidirectionality of the reaction (⇌), indicating the reaction is at equilibrium and proceeds in both directions.
  • When a reaction is in equilibrium, the concentrations of the reactants and products remain constant over time but are not necessarily equal.

Equilibrium Expressions

  • The equilibrium constant, K, expresses the ratio of the concentrations of the products to the reactants at equilibrium.
  • An equilibrium constant can be calculated using the equation K = [products] / [reactants], where the concentrations are usually in molarity (M).
  • The concentrations should be raised to the power of their stoichiometric coefficients from the balanced chemical equation.

Interpreting Equilibrium Constants

  • If K » 1, it indicates the equilibrium lies far to the right, which means the concentration of products is much greater than that of reactants. The reaction favours the products.
  • If K « 1, it indicates the equilibrium lies far to the left, meaning the concentration of reactants is larger than that of products. The reaction favours the reactants.
  • If K = 1, it indicates the equilibrium state has equal concentrations of reactants and products.

Changes in Equilibrium

  • Any changes in the reaction conditions such as pressure, temperature, and concentrations of reactants or products can shift the equilibrium position.
  • Le Chatelier’s Principle can be used to predict the changes in equilibrium. It states that if a change is imposed on a system at equilibrium, the system will adjust itself to counteract that change.

Types of Equilibrium

  • In homogeneous equilibrium, all reactants and products are in the same phase.
  • In heterogeneous equilibrium, the reactants and products are in different phases; the concentrations of pure solids and liquids are not included in the equilibrium expression.