1. Chapter 6 Thermochemistry

2. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–2 QUESTION

3. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–3 ANSWER – q 4)15.2 J. Section 6.1 The Nature of Energy (p. 229) When = 0, then the internal energy equals the work.

4. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–4 QUESTION

5. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–5 ANSWER 3)2 Section6.1 The Nature of Energy (p. 229) The original experiment determining that heat was not a state function was conducted during the boring of cannons. It was found that if the drill was dull, heat could be produced indefinitely without boring deeper into the metal.

6. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–6 QUESTION

7. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–7 ANSWER E qw 3)  = 35 kJ. Section 6.1 The Nature of Energy (p. 229) Internal energy = +. The heat and work both have a positive sign indicating energy flowed from the system to the surroundings.

8. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–8 QUESTION

9. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–9 ANSWER 3)The system does work on the surroundings when an ideal gas expands against a constant external pressure. Section 6.1 The Nature of Energy (p. 229) The gas molecules of the atmosphere have an average distance from each other.

10. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–10 ANSWER (continued)

11. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–11 QUESTION

12. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–12 ANSWER  ) 3)A bomb calorimeter measures H directly. Section6.2Enthalpy and Calorimetry(p. 235 Enthalpy is heat at constant pressure. The pressure can change drastically inside of a bomb calorimeter.

13. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–13 QUESTION

14. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–14 ANSWER ) 3)461 J/g Section6.2Enthalpy and Calorimetry(p. 235 The heat of fusion of the ice is found indirectly from the heat loss of the water.

15. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–15 QUESTION

16. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–16 ANSWER E . E 3) = +4 kJ Section 6.1 The Nature of Energy (p. 229) For a thermodynamic process we are only interested in the change of energy, E is the energy of a particular state.

17. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–17 QUESTION

18. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–18 ANSWER ) 3)The chemical reaction is absorbing energy. Section6.2Enthalpy and Calorimetry(p. 235 The temperature drops because the reactants are absorbing energy from the solution faster than the surroundings can replace it.

19. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–19 QUESTION

20. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–20 ANSWER ) 2) the work done in pushing back the atmosphere. Section6.2Enthalpy and Calorimetry(p. 235 The gas molecules need to use some energy to move atmospheric gas molecules out of their way.

21. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–21 QUESTION

22. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–22 ANSWER qs   Tqs   T  5)still a liquid. Section 6.2 Enthalpy and Calorimetry (p. 235) = m. = 5.0 kJ, = 4.184 J/gC and m = 15.5 g. Solving for  shows that the water was not raised to the 100C necessary for boiling.

23. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–23 QUESTION

24. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–24 QUESTION (continued)

25. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–25 ANSWER ) 1)All are true. Section6.2Enthalpy and Calorimetry(p. 235 The minus sign indicates that the reaction is exothermic.

26. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–26 QUESTION

27. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–27 ANSWER 2) 0.13 J/g  C Section6.2Enthalpy and Calorimetry(p. 235) A common mistake is attempting to solve for the heat capacity instead of specific heat capacity. Using and keeping track of the units of measure takes care of this type of problem. 2)0.13 J/gC Section6.2Enthalpy and Calorimetry(p. 235 A common mistake is attempting to solve for the heat capacity instead of specific heat capacity. Using and keeping track of the units of measure

28. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–28 QUESTION

29. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–29 ANSWER – ) 2)413 kJ Section6.2Enthalpy and Calorimetry(p. 235 Don’t forget to convert grams to moles in this problem. Enthalpy is always in units of kJ/mol.

30. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–30 QUESTION

31. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–31 ANSWER 3) –44.0 kJ Section 6.2 Enthalpy and Calorimetry (p. 235) A common mistake is use the wrong sign for the enthalpy. Careful reading of the problem will indicate the sign that must be used. 44.0 kJ3) Section 6.2 Enthalpy and Calorimetry (p. 235) A common mistake is use the wrong sign for the enthalpy. Careful reading of the problem will indicate the sign that must be used. 44.0 kJ

32. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–32 ANSWER (continued)

33. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–33 QUESTION

34. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–34 QUESTION (continued)

35. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–35 ANSWER H calc ) 4)  would be less positive because the reaction absorbs heat from the calorimeter. Section6.2Enthalpy and Calorimetry(p. 235 Most calorimeters are at least partly made of metal and metals have high thermal conductivity, so ignoring the heat loss to the calorimeter will lead to poor accuracy in your results.

36. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–36 QUESTION

37. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–37 QUESTION

38. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–38 ANSWER 1  –  3 ) – 4)  H + 2 H 2 H Section6.3Hess’s Law(p. 242 The final equation is found by summing the reactions as follows: I + 2(II) III. The minus sign means the reaction is reversed.

39. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–39 QUESTION

40. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–40 ANSWER ) –290 kJ Section6.4Standard Enthalpies of Formation (p. 246 Remember to multiply the heat of formation of each compound by its coefficient.

41. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–41 QUESTION

42. Copyright © Houghton Mifflin Company. All rights reserved.CRS Question, 6–42 ANSWER 5)Carbon dioxide Section 6.6 New Sources of Energy (p. 256) Carbon dioxide is a very stable product of most combustion reactions. It will not react further to produce more useful heat.