The energies of activation for forward and reverse reactions for A2+B2⇌2AB are 180 kJ mol−1 and 200 kJ mol−1 respectively. The presence of a catalyst lowers activation energy of both reactions by 100 kJ mol−1. The enthalpy change of the reaction (A2+B2→2AB) in the presence of a catalyst will be (in kJ mol−1)
20
A2+B2⇌2AB
Ea1=180 kJ mol−1Ea2=200 kJ mol−1
Enthalpy of πxn=Ea2−Ea1=200−180=20 kJ mol−1
By having a catalyst, both activation energies lower by the same amount, so the difference doesn't change
Ans →20 kJ mol−1