Imagine being able to use your computer to make phone calls with the help of special software and a microphoneâand bypassing your phone company and their charges.
So O2 has zero of heat of formation (or enthalpy of formation). The enthalpy of a reaction is defined like this: H = Hproducts-H reactants. The enthalpy of reaction in this case, is the same as the heat of combustion. Hproducts is obtained summing the heats of formation.
There are two main types of heat engines: external combustion and internal combustion: 1  In an external combustion engine, the fuel burns outside and away from the main bit of the engine where the force and motion are produced. 2  In an internal combustion engine, the fuel burns inside the cylinder.