The activation energy for the reaction no2(g)+co(g)⟶no(g)+co2(g) is ea = 175 kj/mol and the change in enthalpy for the reaction is δh = -200 kj/mol . what is the activation energy for the reverse reaction?

375 kJ/mol

Explanation:

1) δh = -200 kj/mol means that the reaction is exothermic and the products of the forward reaction are 200 kJ/mol lower in the potential energy diagram.

2) The reverse reaction must compensate the 200 kJ/mol and go upper as much as the activation energy of the forward reaction.

You can see the attache diagram to verify that

        Ea reverse = Ea forward + | δh |

        Ea reverse = 175 kJ / mol + | -200 kJ/mol | = 175 kJ/mol + 200 kJ/mol = 375 kJ/mol, which is the answer.