2. A fired heater currently uses natural gas as a fuel. Hydrogen is being considered as a replacement fuel, either in a mixture with the natural gas, or as a full replacement. a. How does the air/fuel ratio, and heating value per m3 of fuel change for 0%, 5%, 50% and 100% H2? All percentages are by volume, and the balance is natural gas which in this example can be considered to be equivalent to methane. The heat of combustion is 604 kJ mol-1 for methane and 240 kJ mol-1 for hydrogen