Which reactions are endothermic? (Select all that apply.) And why???!!

H2(g) + ½O2(g)H2O(g),H = -57.83 kcal/mole
½ N2(g) + ½O2(g)NO(g),H = +21.6 kcal/mole
½N2(g) + O2(g) + 8.1 kcalNO2(g)
½N2(g) + 3/2 H2(g)NH3(g) + 11.0 kcal/mole
NH3(g)½N2(g) + 3/2 H2(g),H = +11.0 kcal/mole

Question

Which reactions are endothermic? (Select all that apply.) And why???!!

H2(g) + ½O2(g)H2O(g),H = -57.83 kcal/mole
½ N2(g) + ½O2(g)NO(g),H = +21.6 kcal/mole
½N2(g) + O2(g) + 8.1 kcalNO2(g)
½N2(g) + 3/2 H2(g)NH3(g) + 11.0 kcal/mole
NH3(g)½N2(g) + 3/2 H2(g),H = +11.0 kcal/mole

anonymous · Answer

Simple,Positive enthalpy change denotes endothermic reactions and negative enthalpy change denotes exothermic reaction.Because,negative energy signifies heat release and positive,heat absorption.

anonymous · Answer

thx I was really confused