Which of the following reaction(s) is/are endothermic? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

(a) $N_2$ + $O_2$ -> 2$NO$: Endothermic (δ H = +180.5 kJ). (b) $CaCO_3$ decomposition: Endothermic (δ H = +178 kJ). (c) $CO$ combustion: Exothermic. (d) Hydrogenation of ethylene: Exothermic.