In the field of chemistry, Le Chatelier’s principle is also known as the Equilibrium Law. It is helpful in predicting the effect of a change in conditions on the chemical equilibrium. This principle was named after Henry Louis Le Chatelier and Karl Ferdinand Braun.
It is stated as: When a change in concentration, temperature, volume, or pressure is subjected to a system at equilibrium, then the system tends to readjust itself for counteracting the effect of the applied change for the establishment of a new equilibrium.
In other words, when a system in equilibrium is disturbed, the system tends to adjust itself in such a way that the effect of that change gets nullified. In chemistry, the principle is used for manipulating the outcomes of the reversible reactions for increasing the yield in reactions.
It also implies that the addition of heat to a reaction would favour endothermic direction of a reaction, owing to the reduction in the amount of heat produced in the system. With increase in the concentrations of reactants, the reaction will be driven towards right but with increase in the concentration of the products, the reaction will be driven towards left.
CHANGES IN CONCENTRATION
It means that adding the additional reactant to a system results in shifting the equilibrium to right, towards the side of the products. Also, reducing the concentration of the product will shift the equilibrium to right.
According to the Le Chatelier’s principle, the reversible reaction is self correcting in nature. The observation is also supported by the collision theory.
CHANGES IN PRESSURE
Any change in pressure or volume results in attempting to restore the equilibrium by creating more or lesser moles of gas. If the pressure in a system increases, volume gets decreased and the equilibrium shifts for favouring the side of reaction involving few moles of gas.
ADDITION OF AN INERT GAS
An inert gas does not react with either the reactants or the products thus having no effect on the product/reaction ratio. Therefore, there would be no effect on the equilibrium.
CHANGES IN TEMPERATURE
The effect of temperature on the equilibrium is related to the heat of the reaction. For an endothermic reaction, heat gets absorbed in the reaction, thus the value of H is positive. In an exothermic reaction, the heat gets realised in the reaction making heat a product and thus the value of H is negative.
Adding a catalyst makes no difference to the position of the equilibrium.