(A)Na+H2O⟶NaOH+12H2ΔH∘=−146kJ(B)Na2SO4+H2O⟶2NaOH+SO3ΔH∘=+418kJ(C)2Na2O+2H2⟶4Na+2H2OΔH∘=+259kJ (1)+823kJ(2)−581kJ(3)−435kJ(4)+531kJ