A fuel gas containing 95 mole% methane and the balance ethane is burned completely with 25% excess air. The stack gas leaves the furnace at 900C and is cooled to 450C in a wasteheat boiler. For a 100 moles of fuel into the furnace; 1. Calculate the number of moles of oxygen in the product gas [5 marks] 2. Calculate the total enthalpy change(kJ) for carbon dioxide due to the cooling process