Chemical Equilibrium

Understanding Chemical Equilibrium

  • Chemical equilibrium is a state in which both the reactants and products are present in concentrations that have no further tendency to change with time.
  • The rate of the forward reaction is equal to the rate of the reverse reaction in a system at chemical equilibrium. Both reactions are occurring but there is no net change.
  • Equilibrium does not mean the concentrations of the reactants and products are equal, but that they are constant.
  • Dynamic equilibrium refers to a state of balance between continuing processes, in this case, the forward and reverse reactions.

Le Chatelier’s Principle

  • Le Chatelier’s Principle states that if a system at equilibrium is subject to change, the system will adjust itself in a way that counteracts the change and a new equilibrium is established.
  • Changes can include concentrations of reactants or products, temperature, and pressure. The system responds to minimise these changes.
  • If you increase the concentration of reactants, the equilibrium will shift to the right, increasing the concentration of products.
  • If the temperature is increased, the equilibrium will shift in the direction of the endothermic reaction (absorbs heat) to reduce the temperature.

The Equilibrium Constant (Kc)

  • The equilibrium constant, Kc, quantifies the relationship between the concentration of reactants and products at equilibrium.
  • For a reaction aA + bB ⇌ cC + dD, the Kc expression is Kc = [C]^c [D]^d / [A]^a [B]^b.
  • The values in square brackets represent the molar concentrations of the reactants and products.
  • Kc values are temperature dependent.

Chemical Equilibrium in Industrial Processes

  • Understanding chemical equilibrium is crucial for predicting how changes will affect industrial chemical processes.
  • The principle of chemical equilibrium helps us understand and control industrial processes such as the manufacture of ammonia (Haber process) and sulphuric acid (Contact process).
  • By manipulating conditions (temperature, pressure, concentration), the yield of desired products can be maximised, adding efficiency and profitability.
  • Safety in industrial processes is also tied to understanding chemical equilibrium, as unforeseen changes could lead to dangerous conditions.