Question

Which reaction is endothermic?

A. H2(g) + ½ O2(g) → H2O(g), ΔH = -57.82 kcal
B. ½N2(g) + O2(g) + 8.1 kcal → NO2(g)
C. ½N2(g) + 3/2H2(g) → NH3(g) + 11.0 kcal
D. C(diamond) + O2(g) → CO2, ΔH = -94.50 kcal

Answer 1

B. ½N2(g) + O2(g) + 8.1 kcal → NO2(g)

Step-by-step explanation:

Endothermic means that you are absorbing energy. Thus, the answer cannot be A or D, as energy is released, as indicated by a negative enthalpy.

In C, energy is produced(aka released), and this means it is exothermic.

Thus, the answer must be B, where energy is required to produce NO2(meaning it is absborbed.