Chapter 4 Key - Chapter 4 Homework Key 1. 2. Calories are a...

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Chapter 4 Homework Key 1. Calories are a measure of the energy content of food. 2. kJ 2510.4 kcal 1 kJ 4.184 x 600kcal kcal 600 Cal 600 = = This is less than the Swiss chocolate bar. 3. potential energy stored in fuel is converted to heat energy in the burner/boiler heat energy is converted to mechanical energy as the steam turns the turbine mechanical energy is converted to electrical energy as the turbine runs the generator 4. __________________ 2NO Energy difference = 180kJ __________________ N 2 + O 2 5. a. endothermic – energy is added to convert from liquid to gas b. exothermic – energy is released as fuel is burned c. exothermic – liquid water has more energy than ice, so energy is released as water freezes d. endothermic – energy from the sun is needed 6. a. 2 H H H H H H C C C C C H H H H H H | | | | | | | | | | - - - - - - + 11 .. .. O O .. .. = 10 .. .. O C .. .. + 12 .. H O H - - ..
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Energy to break bonds: 12 C-H bonds x 2 moles x 416 kJ/mole = 9984 kJ 4 C-C bonds x 2 moles x 356 kJ/mole = 2848 kJ 1 O=O bond x 11 moles x 498 kJ/mole = 5478 kJ Total = 18,310 kJ Energy from bonds formed: 1 C≡O bond x 10 moles x (-1073 kJ/mole) = -10,730 kJ 2 O-H bonds x 12 moles x (-467 kJ/mole) = -11,208 kJ Total = -21,938 kJ Net energy change: 18,310 – 21,938 = -3628 kJ exothermic b. 2 H-H + .. .. O
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Chapter 4 Key - Chapter 4 Homework Key 1. 2. Calories are a...

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