Equilibrium

Understanding Chemical Equilibrium

  • Chemical equilibrium is reached when the forward and backward reactions occur at the same rate.
  • In a state of equilibrium, the concentrations of products and reactants remain constant, but are not necessarily equal.
  • A dynamic equilibrium exists when the rate of forward reaction is equal to the rate of the backwards reaction.
  • Dynamic equilibrium means that the reaction hasn’t stopped, it just that there’s no overall change in amounts of reactants and products.

Le Chatelier’s Principle

  • Le Chatelier’s Principle predicts how changes in conditions can shift the position of equilibrium to either the right (formation of more products) or the left (formation of more reactants).
  • If a system at equilibrium is disturbed, it will adjust to counteract the change and restore equilibrium. This is known as Le Chatelier’s principle.
  • Changing concentration, pressure, or temperature can all lead to a shift in equilibrium.

Changing Concentration

  • Increasing the concentration of reactants results in a shift to the right, thus producing more products. Conversely, increasing the concentration of products results in a shift to the left, making more reactants.
  • If a system is in equilibrium and a reactant or product is added, the system will shift to counteract the change and restore equilibrium.

Changing Pressure

  • Increasing the pressure favours the reaction that produces fewer gas molecules, while reducing pressure favours the reaction that produces more gas molecules.
  • This principle only applies to reactions involving gases.

Changing Temperature

  • Increasing the temperature favours the endothermic reaction (absorbs heat), while decreasing the temperature favours the exothermic reaction (releases heat).
  • Changing the temperature also changes the value of the equilibrium constant.

Equilibrium Constant (Kc)

  • The equilibrium constant (Kc) is a measure of the ratio of products to reactants at equilibrium.
  • This constant is temperature dependent and does not change unless the temperature changes.
  • The equilibrium constant is obtained by dividing the concentration of the products by the concentration of the reactants.