# Calculate the energy in kJ that is released as heat (70%) by the combustion of exactly 1 gallon of gasoline. The combustion of gasoline releases and only about 30% of the energy from gasoline is used as work with the rest expelled as heat. The chemical reaction of combustion is: 2 C8H18(l) + 25 O2 (g) → 16 CO2 (g) + 18 H2O (g) H = –10110 kJThe density of octane is 0.702 g/mL. Assume gasoline is pure octane (1 gallon = 3.7854 L). When gasoline, which is taken to be pure octane, undergoes combustion in an internal combustion engine 30% of the energy released is converted to mechanical work and the rest is expelled as heat. 1 gallon of octane is 3.7854 L and the density of octane is 0.702 kg/L

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When gasoline, which is taken to be pure octane, undergoes combustion in an internal combustion engine 30% of the energy released is converted to mechanical work and the rest is expelled as heat. 1 gallon of octane is 3.7854 L and the density of octane is 0.702 kg/L

From the chemical equation:

2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(g) `Delta H`=–10110 kJ

The molar mass of octane is 114 g/mole. The mass of 1 gallon of gasoline is 2.657 kg. This is approximately 2.657/114 = 23.31 moles of octane. Each mole of octane releases (10110/2)*0.7 = 5055*0.7 = 3538.5 kJ of heat.

23.31 moles releases 3538.5*23.31 = 82482.43 kJ of heat.

The amount of heat released when one gallon of gasoline is burnt is approximately 82482.43 kJ

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