Factors affecting Equilibrium:-

1. Le Chatelier’s principle:- It states that if a system in equilibrium is subjected to a change in any of the factors that determine the equilibrium condition of a system, then the equilibrium will shift in the direction so as to undo the effect of change imposed.

This principle is very helpful in predicting the quantitative effect of change in concentration, pressure or temperature.

For example:- 1) Effect of change in concentration :

When concentration of any reactant species is increased the equilibrium shifted to that direction to undo the effect of change imposed.

For example:- In the equilibrium reaction,

When H₂ is added, equilibrium shifted to forward direction & when HI is added to reaction mixture, equilibrium shifted to backward direction.

Sweet substances cause tooth decay, tooth enamel consists of an insoluble substance called hydroxypetite = Ca₅(PO₄)₃OH

When sugar substances are taken, sugar is absorbed on when sugar substances to give H⁺ ion. When H⁺ ion combine with OH^- ion, the equilibrium shifted to the forward direction & cause tooth decay.

2) Effect of temperature on equilibrium:- If temperature of the system at equilibrium is increased the equilibrium shift in the direction in which the heat is absorbed while decreased in the temperature will shift to the equilibrium towards the direction in which heat is produced and therefore will favour exothermic reaction.

When the temperature of the reaction vessel is increase equilibrium shifted to backward direction, but when the temperature of the reaction vessel is decreased, equilibrium shifted to forward direction.

Or

If temperature is increased, equilibrium shifted to forward direction & vice-versa.

With ↑ in temperature, solubility of NH4Cl in water increases. While with ↓in temperature solubility decreases.

3)Effect of catalyst:- Catalyst has no effect on equilibrium because catalyst favour the rate of forward reaction & backward reaction equally & doesn’t affect the position of equilibrium .

4.)Effect of addition of inert gas:-

Addition of inert gas at constant volume. When an inert gas is added to the equilibrium system at constant volume then, the total pressure will increase but the concentration reactant & product will not change. Hence, under these conditions there will be no effect on equilibrium.

 Addition of inert gas at constant pressure:- when an inert gas is added to the equilibrium system at constant pressure then the volume will increase result, no of moles per unit volume of the various reactant & product will decreases. Hence, the equilibrium will shift in a direction in which there is increase in no. of moles of gases.

Equilibrium shifted to forward direction on addition of inert gas at constant pressure.

5)Effect of pressure:- If the pressure on a system increases, the equilibrium will shift in the direction in which pressure is reduced as the pressure of gaseous system increases, the equilibrium shifted to that direction in which the no. of moles per unit volume decreases.

With ↑ in pressure, equilibrium shifted to backward direction & vice-versa.