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Problem 99

The air bags that provide protection in automobil…

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Problem 98

The automobile fuel called $E 85$ consists of 85$\%$ ethanol and 15$\%$ gasoline. E85 can be used in the 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 $\mathrm{C}_{8} \mathrm{H}_{18} ),$ that the average heat of combustion of $\mathrm{C}_{8} \mathrm{H}_{18}(l)$ is 5400 $\mathrm{kJ} / \mathrm{mol}$ , and that gasoline has an average density of 0.70 $\mathrm{g} / \mathrm{mL}$ . The density of ethanol is 0.79 $\mathrm{g} / \mathrm{mL}$ . (a) By using the information given as well as data in Appendix $\mathrm{C},$ compare the energy produced by combustion of 1.0 L of gasoline and of 1.0 . of ethanol. (b) 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 E85? (\mathbf{c} ) How many gallons of E85 would be needed to provide the same energy as 10 gal of gasoline? (d) 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?

Answer

(a)$$2.1 \times 10^{4} \mathrm{kJ}$$
(b)$$2.3 \times 10^{4} \mathrm{kJ}$$
(c)14 gallons E85
(d)$\$ 4.34$


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