Which reactions are endothermic? (select all that apply.) a. h2(g) + ½o2(g) h2o(aq), h = -57.83 kcal/mole b. ½ n2(g) + ½o2(g) no(g), h = +21.6 kcal/mole c. ½n2(g) + o2(g) + 8.1 kcal no2(g) d. ½n2(g) + 3/2 h2(g) nh3(g) + 11.0 kcal/mole e. nh3(g) ½n2(g) + 3/2 h2(g), h = +11.0 kcal/mole