Which of the following reactions represents an exothermic reaction? 1.) C + 2S → CS 2, ΔH = 27,550 cal 2.) 2H 2O → 2H 2 + O 2, ΔH = +58 kcal 3.) C (graphite) → C (diamond), ΔH = 0.45 kcal 4.) NH 3(g) + 12.0 kcal → ½N 2(g) + 3/2H 2(g) 5.) CH 4 + 2O 2 → CO 2 + 2H 2O + 212,800 cal