The automobile fuel called E85 consists of 85% enthanol and 15% gasoline. E85 ca

Question

The automobile fuel called E85 consists of 85% enthanol and 15% gasoline. E85 can be used in the so-called flex-fuel vehicles (FFV_s), which can use gasoline, ethanol, or a mix as fuels. Assume that gasoline consists of a mixture of octanes (different isomers of C_8H_18), that the average heat of combustion of C_8H_18 (I) is 5400 kj/mol, and that gasoline has an average density of 0.70g/mL. The density of ethanol is 0.79g/mL. By using the information given as well as data in Appendix C, compare the energy produced by combustion of 1.0 L of gasoline and of 1.0 L of ethanol. Assume that the density and heat of combustion of E85 can be obtained by using 85% of the values for ethanol and 15% of the values for gasoline. How much energy could be released by the combustion of 1.0 L of E 85 ? How many gallons of E85 would be needed to provide the same energy as 10 gal of gasoline? If gasoline costs $3.88 per gallon in the United States, what is the break-even price per gallon of E85 if the same amount of energy is to be delivered?

Explanation / Answer

gasoline provides 6.6x10^4 kJ of energy and E85 provides 4.2x10^4 kJ

10 gal gasoline * 6.6x10^4 kJ / 4.2 * 10^4 kJ

gasoline has a higher energy content per gallon so you need more gallons of E85 to provide the same energy.

It takes 14 gallons of E85 to equal the energy of 10 gallons of gas.

Doing a conversion of 14 gallons of e85 over 10 gallons of gas and multiply by 1 gallon of gas per 3.10 dollars. This gives gallons of e85 per dollar which you can flip to get dollars per gallon of e85 (or you can flip the initial multiplication).

Answer is about 2.2 dollar

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