The combustion of gasoline releases tremendous amounts of heat. It is the work done on the piston that is the main goal of the reaction, so systems are developed to remove the excess heat produced, since only about 30% of the energy from gasoline is used as work.
2 C8H18 (l) + 25 O2 (g) → 16 CO2 (g) + 18 H2O (g) H = –10110 kJ
A)Calculate the energy in kJ that is released as heat (70%) by exactly 1 gallon of gasoline. The density of octane is 0.702 g/mL. We will assume for now that gasoline is pure octane. (1 gallon = 3.7854 L)
B)Most of the heat calculated in part a. goes right out the exhaust system and into the air. About 25% of the heat gets absorbed into the metal parts that make up your engine. Let's approximate that the mass of your engine is 79.8 lbs with a uniform specific heat of near 0.43 J/g x °C. If your engine begins at 25 °C, how hot will your engine be if it continuously burns 5.5 gallons of gasoline (octane) while driving? (1 lb = 0.4536 kg)
2007-04-25 16:07:31 · 2 answers · asked by SUKE! 1 in Science & Mathematics ➔ Chemistry
A) 1 gallon weighs 2657.35 g
Molar mass of C8H18 = 114
Thus heat released = .7*10110*2657.35/228 = 82.48 kJ
B) Temp = .25*5.5*82480/(79.8*0.4536*.43) + 25 = 7311 deg C
2007-04-25 21:35:11 · answer #1 · answered by ag_iitkgp 7 · 0⤊ 0⤋
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2016-12-10 11:42:41 · answer #2 · answered by Anonymous · 0⤊ 0⤋