Explanation:
Le Chatelier's principle provides an indept investigation to effect of changing conditions on equilibrium.
According to his principle, he postulated that "If any conditions of a system in equilibrium is changed, the system will adjust itself in order to annul the effect of the change".
In a system in equilibrium, the changing conditions are usually concentration, temperature and pressure. These changing conditions imposes stress on a system.
If any system is placed on this stress, the equilibrium shifts to counteracts the effect of the stress.
When the temperature of an exothermic reaction is increased:
An exothermic reaction is one in which heat is given off. The heat of the products is greater than heat of the reactants.
Let us use the Haber process in which ammonia is produced as an example:
N₂ + 3H₂ → 2NH₃ ΔH° = -91kJmol⁻¹
A change in temperature shifts the equilibrium to a new point.
An increase in temperature shifts the equilibrium backward because in the reverse direction heat is absorbed i.e endothermic. Increase in temperature would lead to production of more ammonia and the equilibrium would have to readjust to compensate for the reactants that are being used. This is why the equilibrium would shift backward in order to annul the effect of the increasing temperature.
