Which of the following reactions is endothermic? h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal ½n2(g) + o2(g) + 8.1 kcal → no2(g) ½n2(g) + 3/2h2(g) → nh3(g) + 11.0 kcal c(diamond) + o2(g) → co2, δh = -94.50 kcal