The enthalpy change for a chemical reaction is the sum of the energy consumed in breaking bonds and the energy released during bond formation. One way to determine the overall energy change for a chemical reaction is to apply Hess’s law to add together a group of reactions which can be arranged such that the chemical equations, when combined, give the overall equation we are trying to characterize. The average propane cylinder for a residential grill holds approximately 18 kg of propane. How much energy (in kJ) is released by the combustion of 19.00 kilograms of propane in sufficient oxygen?