Many power plants produce energy by burning carbon-based fuels, which also produ

Question

Many power plants produce energy by burning carbon-based fuels, which also produces carbon dioxide. Carbon dioxide is a greenhouse gas, so over-production can have negative effects on the environment. Use enthalpy of formation data to calculate the number of moles of CO2(g) produced per megajoule of heat released from the combustion of each fuel under standard conditions (1 atm and 25 degree C). coal, C(s, graphite); natural gas, CH4(g); propane, C3H8(g); octane, C8H18(l) (Delta = -250.1 kJ·mol-1).

Explanation / Answer

a) C + O2 --------> CO2 enthalpy of reaction = -393.509 KJ/mol 1 mol CO2 is released when 0.393509 MJ of heat is liberated so number of moles of CO2 formed when 1MJ heat is released = 1/0.393509 = 2.54 moles b) CH4 + 2O2 ----------> CO2 + 2H2O enthalpy of reaction = (enthalpy of formation of CO2) + 2*(enthalpy of formation of H2O) - (enthalpy of formation of methane) = -393.509 +2(-285.53) -(-75.2) = -889.37KJ 1 mol CO2 is released when 0.88937 MJ of heat is liberated so number of moles of CO2 formed when 1MJ heat is released = 1/0.88937 = 1.124 moles c) C3H8 + 5O2 ---------> 3CO2 + 4H2O enthalpy of reaction = 3*(enthalpy of formation of CO2) + 4*(enthalpy of formation of H2O) -(enthalpy of formation of methane) 3*(-393.509) + 4(-285.53) -(-105) = -2217.65KJ 3 mol CO2 is released when 2.22 MJ of heat is liberated so number of moles of CO2 formed when 1MJ heat is released = 3/2.22 = 1.351 moles d) C8H18 + 12.5O2 ---------> 8CO2 + 9H2O enthalpy of reaction = 8*(enthalpy of formation of CO2) + 9*(enthalpy of formation of H2O) -2*(enthalpy of formation of OCTANE) 8*(-393.509) + 9(-285.53) -2(-250.1) = -5217.642KJ 8 mol CO2 is released when 5.22 MJ of heat is liberated so number of moles of CO2 formed when 1MJ heat is released = 8/5.22 = 1.53 moles

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