Equilibrium Concentrations (Le Chatelier's Principle)

Equilibrium Concentrations (Le Chatelier’s Principle)

  • Le Chatelier’s Principle states that a system at equilibrium will adjust in order to counteract a change applied to it. This means if you alter things like concentration, temperature, or pressure, the position of equilibrium will shift to reduce this change.

  • If the concentration of a reactant in a chemical reaction at equilibrium is increased, the reaction will shift to decrease this concentration by favouring the forward reaction (products are formed at a faster rate).

  • On the other hand, if the concentration of a product is increased, the reaction will favour the reverse reaction (reactants are formed at a faster rate)

  • Conversely, if the concentration of either a reactant or product is decreased, the reaction will counteract this by shifting the equilibrium position to increase this concentration.

  • Similarly, the position of equilibrium will also change if the volume or pressure of the system is altered. If the volume is decreased (pressure increased), the equilibrium will shift to the side with less moles of gas. If the volume is increased (pressure decreased), the equilibrium will shift to the side with more moles of gas.

  • It’s important to remember that the principle doesn’t predict how far the equilibrium will move, it only predicts the direction of the shift.

  • Le Chatelier’s Principle is central to many industrial processes, as it allows chemists to manipulate conditions to obtain the maximum yield of desired product.

  • Understanding and applying Le Chatelier’s Principle requires a solid grasp of equilibrium constants and how they relate to the concentration of reactants and products. Remember that the constant Kc represents the ratio of product concentrations to the reactant concentrations, each raised to the power of their stoichiometric coefficient in the balanced chemical equation.

  • Do not confuse Le Chatelier’s Principle with the idea of the rate of the reaction. The principle relates only to the position of equilibrium and does not tell you anything about how quickly that position will be reached.