Combustion reactions are endothermic reactions which means they release heat as the reaction proceeds to completion. To determine which hydrocarbon would provide more or release the most heat when allowed to react with oxygen, we need the values of the heat of combustions of the compounds given above. From literature, we would find the following values.
C6H14 = -4163.2 kJ /molC6H12 = -3919.6 kJ /mol
C2H6 = -1560 kJ /mol
C3H8 = -2220.1 kJ /mol
The negative value would represent that the certain value of heat is being released during the reaction. From the list, C6H14 would be the one to provide the most heat.
