Le Chatelier Principle Equilibrium Reactions

Le Chatelier Principle Statement

How the system behave if any of the parameters of the system at equilibrium be altered was first predicts by Le Chatelier in 1885 and Braun in 1886. They made a general statement as

At equilibrium, a change in any factors that determine the condition of equilibrium will cause the equilibrium to shift in such a way as to minimize the effect of this change.

The general statement of this principle and applicable to all systems to predict their behavior when parameters changed but chemical kinetics predict the rate of reaction with time. We shell predict use this principle to express the effects of pressure, temperature, and concentration on the chemical equilibrium.

Example of Le Chatelier principle

Let us take an example for the synthesis of ammonia to illustrate Le Chatelier principle

Effect of temperature on equilibrium

This is an exothermic reaction. If the temp is raised, according to the Le Chatelier principle, the system would behave in a way to absorbed and utilize this specific heat.

This means dissociation of ammonia molecules would occur. In fact, less ammonia is produced at equilibrium at higher temperatures. It may be stated as

When the temperature of a system in equilibrium increases, the equilibrium shifted in a direction that absorbed heat.

But Van’t Hoff equation provides the change of temperature with the equilibrium constant of a chemical reaction.

Effect of Pressure on equilibrium

If the pressure in the system at equilibrium increased, the system would tend to nullify the effect of pressure. In this system, the volume would be diminished if the number of the molecule decreases. Therefore with the increasing pressure equilibrium will shift in a direction to produce more ammonia.

When the pressure of a system at equilibrium increases, the equilibrium shifted in the direction to reduce the number of molecules in the system.

Effect of reacting components on equilibrium

If ammonia or hydrogen is added to this system from external sources, then the partial pressure of the said component would increases. according to the Le Chatelier principle, the system would attempt to use up this component for chemical bonding.

The addition of reactant or product to a system in equilibrium causes the equilibrium to shift in the direction that decreases the concentration of the added component.