The energies of activation for forward and reverse reactions for $${A_2} + {B_2} \rightleftharpoons 2AB$$    are $$180\,kJ\,mo{l^{ - 1}}$$   and $$200\,kJ\,mo{l^{ - 1}}$$   respectively, The presence of catalyst lowers the activation energy of both (forward and reverse) reactions by $$100\,kJ\,mo{l^{ - 1}}$$  . The enthalpy change of the reaction $$\left( {{A_2} + {B_2} \to 2AB} \right)$$    in the presence of a catalyst will be ( in $$kJ\,mo{l^{ - 1}}$$  )