In the manufacture of nitric acid by the oxidation of ammonia, the first product is nitric oxide. The nitric oxide is then oxidized to nitrogen dioxide:

2 NO(g) + O2(g) → 2 NO2(g)

Calculate the standard reaction enthalpy for the reaction above (as written) using the following data:
N2(g) + O2(g) → 2 NO(g) ∆H ◦ = 180.5 kJ
N2(g) + 2 O2(g) → 2 NO2(g) ∆H◦ = 66.4 kJ

(A) −128.2 kJ/mol rxn
(B) −100.3 kJ/mol rxn
(C) −520.2 kJ/mol rxn
(D) −252.4 kJ/mol rxn
(E) −690.72 kJ/mol rxn
(F) −114.1 kJ/mol rxn

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

qualitative observation deals with data that can be observed with our senses: sight, smell, touch, taste, and hearing. they do not involve measurements or numbers. for instance, colors, shapes, and textures of objects are all qualitative observations.