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 catalyst lowers the activation energy of both (forward and reverse) reactions by 100 kJ mol^−1. The enthalpy change of the reaction ( A₂ + B₂ 2AB) in the presence of catalyst will be (in kJ mol^−1)