The automobile fuel called E85 consists of 85% ethanol and 15% gasoline. E85 can

Question

The automobile fuel called E85 consists of 85% ethanol and 15% gasoline. E85 can be used in so-called flex-fuel vehicles (FFVs), which can use gasoline, ethanol, or a mix as fuels. Assume that gasoline consists of a mixture of octanes (different isomers of C8H18 ), that the average heat of combustion of C8H18(l) is 5400 kJ/mol , and that gasoline has an average density of 0.70 g/mL . The density of ethanol is 0.79 g/mL .

Part A

By using the information given, calculate the energy produced by combustion of 3.0 L of gasoline.

Express your answer to two significant figures and include the appropriate units.

Energy =

9.9×104 kJ

Part B

By using the information given as well as data in Appendix C, calculate the energy produced by combustion of 3.0 L of ethanol. Consider that water is in the gaseous state.

Express your answer to two significant figures and include the appropriate units.

Energy = 6.4×104 kJ   

Part C

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 3.0 L of E85?

Express your answer to two significant figures and include the appropriate units

Energy =

6.9×104 kJ

Part D

How many gallons of E85 would be needed to provide the same energy as 40 gal of gasoline?

Express your answer to two significant figures and include the appropriate units.

Part E

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?

Express your answer using three significant figures.

Energy =

9.9×104 kJ

Part B

By using the information given as well as data in Appendix C, calculate the energy produced by combustion of 3.0 L of ethanol. Consider that water is in the gaseous state.

Express your answer to two significant figures and include the appropriate units.

Energy = 6.4×104 kJ   

Part C

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 3.0 L of E85?

Express your answer to two significant figures and include the appropriate units

Energy =

6.9×104 kJ

Part D

How many gallons of E85 would be needed to provide the same energy as 40 gal of gasoline?

Express your answer to two significant figures and include the appropriate units.

Part E

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?

Express your answer using three significant figures.

Explanation / Answer

Given that

average heat of combustion of gasoline C8H18(l) is 5400 kJ/mol

average density of gasoline 0.70 g/mL

We have to calculate energy produced by combustion of 3.0 L of gasoline.

Density = mass /volume

mass= density x volume

= 0.7 g/mL x 3.0 L

= 700 g/L x 3 L

= 2100 g

Moles of gasoline = mass/ molar mass of gasoline C8H18

= 2100 g/ 114 g/mol

= 18.4 mol

Hence,

energy produced by combustion of 3.0 L of gasoline = 18.4 mol x 5400 kJ/mol

= 9.9 x 104 kJ

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