Exam 15: Chemical Reactions

A fuel is burned during a steady-flow combustion process. Heat is lost to the surroundings at 280 K at a rate of 920 kW. The entropy of the reactants entering per unit time is 14 kW/K and that of the products is 12 kW/K. The total rate of exergy destruction during this combustion process is

Benzene gas (C₆H₆) is burned with 85 percent theoretical air during a steady-flow combustion process. The mole fraction of the CO in the products is

Propane C₃H₈ is burned with 120 percent theoretical air. The air-fuel mass ratio for this combustion process is

The higher heating value of a hydrocarbon fuel C_nH_m with m = 8 is given to be 1340 MJ/kmol of fuel. Then its lower heating value is

One kmol of ethane (C₂H₆) is burned with an unknown amount of air during a combustion process. If the combustion is complete and there are 3 kmol of free O₂ in the products, the air-fuel mass ratio is

A fuel is burned with 70 percent theoretical air. This is equivalent to

Methane gas (CH₄) is burned completely during a steady-flow combustion process. The fuel and the air enter the combustion chamber at 25°C, and the products leave at 1500 K. If the enthalpy of the products relative to the standard reference state is -451 MJ/kmol of fuel, the heat transfer from the combustion chamber is

An equimolar mixture of carbon dioxide and water vapor at 2 atm and 45°C enter a dehumidifying section where the entire water vapor is condensed and removed from the mixture, and the carbon dioxide leaves at 2 atm and 45°C. The entropy change of carbon dioxide in the dehumidifying section is

Liquid ethanol (CH₄) is burned completely with 55% excess air during a steady-flow combustion process. If both the reactants and the products are maintained at 25°C and 1 atm and the water in the products exists in the liquid form, the heat transfer from the combustion chamber per unit mass of fuel is

One kmol of ethane (C₂H₆) is burned with air during a combustion process. If the combustion is complete and the air-fuel ratio is 22, the number of moles of free O₂ in the products is