Question

Consider this reaction:

2O₃(g)<--->3O₂(g)

ΔH_rxn=-285.4 kj/mol. In which direction will the reaction shift when the following stresses are combined?

a.Remove ozone from the system

b.Add Ar

c.Decrease temperature

d.Add catalyst

Answer 1

According to the Le-Charterlier's principle,
(1) If the temperature is raised, reaction will proceed in the direction in which some heat can destroy (absorbed) so that temperature of the system remains constant.
Thus increase in temperature shifts the equilibrium in the forward direction of those reactions which proceed with absorption of heat (endothermic reactions), and in the back ward direction of those reactions which proceed with the evolution of heat (exothermic reactions)
(2) If the pressure is increased, reaction will takes place in a direction which will bring about lowering f pressure. This implies that the equilibrium will shifts in the direction which produces the smaller no. of gas molecules.
(3) If the concentration of reactants is increased or product is removed , the reaction will take place in the forward direction. If the concentration of reactants decreases or increasing the concentration of products the reaction will take place in the backward direction.
(4) Catalyst speeds up both forward & backward reactions to the same extent but does not have any effect on Equilibrium point.
(5)---> When the no. of moles of reactants & products are same the addition of inert gas has no effect
----> for a reaction at constant pressure ,addition of an inert gas will shifts the equilibrium in the direction in
which there is increase in the no . of moles of the gases

2O3(g)<--->3O2(g):ΔHrxn=-285.4 kj/mol.

a.Remove ozone from the system---> backward reaction takes place

b.Add Ar ----> forward reaction takes place

c.Decrease temperature----> exothermic --->forward reaction takes place.

d.Add catalyst---->no effect