Ethanol, C,H,O, is most often blended with gasoline usually as a 10 percent mix

Question

Ethanol, C,H,O, is most often blended with gasoline usually as a 10 percent mix - to create a fuel called gasohol. Ethanol is a renewable resource and ethanol-blended fuels, like gasohol, appear to burn more efficiently in internal combustion engines. The combustion enthalpy of ethanol is 1366.9 kJ/mol. Question The combustion enthalpy of 2-methylhexane, C,H16, is 4.812x103 kJ/mol. Calculate the energy released during the complete combustion of 412 g 2-methylhexane. kJ Assuming the same efficiency, would 412 g ethanol provide more, less, or the same quantity of energy as 412 g 2-methylhexane?

Explanation / Answer

1)

mass of 2-methylhexane = 412 g

moles of 2-methylhexane = 412 / 100 = 4.12 mol

1 mol C7H16    ---------------> 4.812 x 10^3 kJ/mol

4.12 mol C7H16 ------------>   ??

Energy released = 4.12 x 4.812 x 10^3

Energy released = 1.98 x 10^4 kJ

2)

Ethanol combustion enthalpy = 1366.9 kJ/mol

moles of ethanol = 412 / 46 = 8.9565 mol

Energy released = 1.224 x 10^3 kJ

Ethanol provide less quantity of energy

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