Determine whether the following are endothermic or exothermic.

Question

2H2O2 (l) �¨ 2H2O(l) + O2(g)
∆H = -190 kj

C(s) + H2O (g) �¨ CO (g) + H2 (g)
∆H = +113 kj

C4H9OH(l) + 6 O2(g) �¨ 4 CO2(g) + 5 H 2O(g)
∆H = -2456.1

2 C(s) + H2(g) �¨ C2H2(g)
∆H = +226.71

N2O5(s) + H2O(l) �¨ 2 HNO3(aq)
∆H = -86.0

thanks!

Answer 1

The endothermic reactions have negative ∆H values, because, for thosue reactions, chemical energy is lost when heats of formation of reactants and products are compared at the same temperature.