We are given with the balanced chemical reaction and the individual enthalpy of formation of the species involved in the reaction. To get the enthalpy of the reaction, the difference between the sum of the enthalpy of formations of the products and the reactants is calculated taking in mind the stoichiometry of the reaction.
∆Hrxn = [2(-411) + (-277)] - [2(-360) + (-359)]
∆Hrxn = -20 kJ
