When boron hydrides burn in air, the reactions are very exothermic.
(a) Write a balanced equation for the combustion of B₅H₉(g) in air to give B₂O₃(s) and H₂O(g).
(b) Calculate the enthalpy of combustion for B₅H₉(g) (Δ_fH° = 73.2 kJ/mol), and compare it with the enthalpy of combustion of B₂H₆ (−2038 kJ/mol). (The enthalpy of formation of B₂O₃(s) is −1271.9 kJ/mol.)
(c) Compare the enthalpy of combustion of C₂H₆(g) with that of B₂H₆(g). Which transfers more energy as heat per gram?