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5 Thermochemistry Solutions to Exercises 7g protein X 17 protein kJ = 119 or 1 kJ total energy = 95.0 kJ + 238 kJ + 119 kJ = 452 or 5 10² kJ 452 kJ 4.184 X 1kcal 1Cal = 108.03 or 1 X 10² Cal/serving Check. 100 Cal/serving is a reasonable result; units are correct. The data and the result have 1 sig fig. (b) Sodium does not contribute to the calorie content of the food, because it is not metabolized by the body; it enters and leaves as 5.84 Calculate the fuel value in a pound of M&M® candies. 320 g carbohydrate 1g carbohydrate 17 kJ = kJ = 5.4 10³ kJ 21 g protein 1g 17 protein kJ = 357 kJ = 3.6 kJ total fuel value = 3648 kJ + 5440 kJ + 357 kJ = 9445 kJ = 9.4 10³ kJ/lb 9445kJ 1lb 42g = 874.5 = kJ/serving lb 453.6 serving serving 4.184 1 kcal 1 1Cal kcal = 209.0 Cal = Cal/serving Check. 210 Cal is the approximate food value of a candy bar, so the result is reasonable. 5.85 Plan. g mol kJ Cal Solve. 16.0 C₆H₁₂O₆ 180.2 1 mol C₆H₁₂O₆ C₆H₁₂O₆ 2812 C₆H₁₂O₆ 1 Cal = 59.7 Cal Check. 60 Cal is a reasonable result for most of the food value in an apple. 5.86 177 mL 1.0 wine 0.106 g ethanol 1 mol ethanol 1367 kJ 1 Cal 1 mL 1g wine 46.1 ethanol 1 mol ethanol 4.184kJ = 133 = 1.3x 10² Cal Check. A "typical" 6 OZ. glass of wine has 150-250 Cal, so this is a reasonable result. Note that alcohol is responsible for most of the food value of wine. 5.87 Plan. Use enthalpies of formation to calculate molar heat (enthalpy) of combustion using Hess's Law. Use molar mass to calculate heat of combustion per kg of hydrocarbon. Solve. Propyne: (a) = + - (185.4 - 4(0) = -1849.5 126