Ethanol, C 2 H 6 O , is most often blended with gasoline - usually as a 10 perce

Question

Ethanol, C2H6O, 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 combustion engines. The heat of combustion of ethanol is 326.7 kcal/mol.

The heat of combustion of heptane, C7H16, is 1.151×103 kcal/mol. How much energy is released during the complete combustion of  416 grams of heptane ?

kcal=

Assuming the same efficiency, would 416 grams of ethanol provide more, less, or the same amount of energy as 416 grams of heptane? _________morelessthe same amount

Explanation / Answer

moles of heptane = 416 / 100.2 = 4.15 mol

1 mol ----------> 1.151 x 10^3 kcal

4.15 mol -------> ??

Q = - n x delta H

   = - 4.15 x 1.151 x 10^3

   = 4778.6

Energy released = 4778.6 kcal

2)

moles of ethanol = 416 / 46 = 9.04 mol

energy = 326.7 x 9.04

Energy = 2954.5 kcal

Ethanol provides less energy than heptane

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