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U2_M2_HW-key

# U2_M2_HW-key - Syn City Part 2-KEY 1 One thing you should...

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“Syn City” Part 2-KEY 1. One thing you should have discovered in part 1 of “syn city” is that when syn gas composition is 80% H 2 , 20% CO, the AF ratio is dependent on the CO concentration as this compound is the limiting reactant in the combustion reaction. a) What is the optimal (stoichiometric) ratio of H 2 to CO so that there is no limiting reactant in the fuel mixture? The optimal mixture is 50:50 by moles since they have a 1:1 ratio in the balance equation. b) Using this ratio, calculate the amount of energy released per mole of syngas combusted. You will need to look up the dissociation energy for the carbon-oxygen triple bond in CO (C≡O) to calculate the heat of reaction H rxn ; the other dissociation energies are listed in the class notes. Compare the energy released by syngas to that of octane, methane, and methanol as listed in the class notes. How would you explain the differences using arguments based on potential energy of the molecules and bond strength? Using bond energies, the ∆H = -394 kJ/mol syngas combusted. This is less than methane (-890 kJ/mol), methanol (-726 kJ/mol) and octane (-5470 kJ/mol). The real difference is due to the stability of the C≡O bond in carbon monoxide. It is already at a very low potential energy state and is not a great component for a fuel. c) Without doing a calculation, would you predict syngas to be as effective as a fuel as pure hydrogen? Why? Support your answer by constructing an energy profile for the reaction.

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