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General Chemistry Principles & Modern Applications 9 th Edition Petrucci/Harwood/Herring/Madura Chapter 19 Spontaneous Change: Entropy and Free Energy.

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Presentation on theme: "General Chemistry Principles & Modern Applications 9 th Edition Petrucci/Harwood/Herring/Madura Chapter 19 Spontaneous Change: Entropy and Free Energy."— Presentation transcript:

1 General Chemistry Principles & Modern Applications 9 th Edition Petrucci/Harwood/Herring/Madura Chapter 19 Spontaneous Change: Entropy and Free Energy Dr. Travis D. Fridgen Memorial University of Newfoundland © 2007 Pearson Education

2 Which of the following processes would you expect to result in a greater positive change in entropy? None of these processes involve positive entropy changes.

3 Which of the following processes would you expect to result in a greater positive change in entropy? None of these processes involve positive entropy changes.

4 Which of the following statements is incorrect? 1.The absolute entropy for gaseous C 2 H 6 is lower than that for gaseous C 3 H 8 at the same temperature. 5.  fus S (solid to liquid) for H 2 O is greater than that for C 3 H 8. 4.The absolute entropy for gaseous C 3 H 8 decreases when the temperature is increased. 2.The entropy of formation for gaseous C 3 H 8 is negative. 3.The entropy of formation of gaseous C 3 H 8 is more negative than the entropy of formation for C 2 H 6.

5 Which of the following statements is incorrect? 1.The absolute entropy for gaseous C 2 H 6 is lower than that for gaseous C 3 H 8 at the same temperature. 5.  fus S (solid to liquid) for H 2 O is greater than that for C 3 H 8. 4.The absolute entropy for gaseous C 3 H 8 decreases when the temperature is increased. 2.The entropy of formation for gaseous C 3 H 8 is negative. 3.The entropy of formation of gaseous C 3 H 8 is more negative than the entropy of formation for C 2 H 6.

6 The entropy change for the decomposition of ozone forming diatomic oxygen, 1.is positive because two moles of gas are forming three moles of gas. 2.is close to zero because there are the same number of atoms on each side of the equation. 3.is negative because energy is released as the reaction proceeds. 4.is close to zero because both ozone and oxygen are in the gas phase. 5.None of the above answers makes sense.

7 The entropy change for the decomposition of ozone forming diatomic oxygen, 1.is positive because two moles of gas are forming three moles of gas. 2.is close to zero because there are the same number of atoms on each side of the equation. 3.is negative because energy is released as the reaction proceeds. 4.is close to zero because both ozone and oxygen are in the gas phase. 5.None of the above answers makes sense.

8 Which of the following reactions, occurring when propane is burned, would you expect to be the most entropically favored (most positive change in entropy)?

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10 In which of the following processes involving CO 2 do you think the standard free energy change not make sense?

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12 Which of the following compounds would obey Trouton’s rule most closely?

13 Which of the following compounds would obey Trouton’s rule most closely?

14 Edgar Fahs Smith Collection University of Pennsylvania Library J. W. Gibbs At room temperature ~290 K the reaction of H 2 and O 2 to form water: 1. is spontaneous because it is exothermic. 2. is non-spontaneous because  S is negative. 3. is spontaneous because  S is negative. 4. is spontaneous because  G is negative. 5. is spontaneous because  G is positive.

15 Edgar Fahs Smith Collection University of Pennsylvania Library J. W. Gibbs At room temperature ~290 K the reaction of H 2 and O 2 to form water: 1. is spontaneous because it is exothermic. 2. is non-spontaneous because  S is negative. 3. is spontaneous because  S is negative. 4. is spontaneous because  G is negative. 5. is spontaneous because  G is positive.

16 Which of the following processes would you expect to be spontaneous at all temperatures? 4. None are spontaneous at all temperatures. 5. All are spontaneous irrespective of the temperature

17 Which of the following processes would you expect to be spontaneous at all temperatures? 4. None are spontaneous at all temperatures. 5. All are spontaneous irrespective of the temperature

18 The transformation between ice and water: 1.Is spontaneous in the directions written because  S is positive. 2.Is spontaneous in the backwards direction because  H is positive. 3.Is spontaneous in the forward direction above 273 K and spontaneous in the backward direction below 273 K. 5.There is not enough information provided to answer this question. 4.All three answers are correct.

19 The transformation between ice and water 1.Is spontaneous in the directions written because  S is positive. 2.Is spontaneous in the backwards direction because  H is positive. 3.Is spontaneous in the forward direction above 273 K and spontaneous in the backward direction below 273 K. 5.There is not enough information provided to answer this question. 4.All three answers are correct.

20 A mixture of H 2 and O 2 can sit in a flask almost indefinitely at 298 K without reacting. What is the best explanation for the absence of observable reaction? ? 3. The reaction is entropically unfavorable. 2. The reaction is not spontaneous at this temperature. 1. A significant energy barrier hinders the start of the reaction. 4. All three of these factors contribute. 5. None of the above answers is correct.

21 A mixture of H 2 and O 2 can sit in a flask almost indefinitely at 298 K without reacting. What is the best explanation for the absence of observable reaction? 3. The reaction is entropically unfavorable. 2. The reaction is not spontaneous at this temperature. 1. A significant energy barrier hinders the start of the reaction. 4. All three of these factors contribute. ? 5. None of the above answers is correct.

22 There is enough energy in lightning bolts that O 2 and N 2 in the atmosphere are decomposed into N and O atoms. The reaction of N and O to form NO, 1. is spontaneous at all temperatures. 2. is non-spontaneous at all temperatures. 3.is spontaneous at high temperatures but non- spontaneous at low temperatures. 4.is spontaneous at low temperatures but non- spontaneous at high temperatures. 5.It is impossible to choose between the above responses without thermochemical data.

23 There is enough energy in lightning bolts that O 2 and N 2 in the atmosphere are decomposed into N and O atoms. The reaction of N and O to form NO, 1. is spontaneous at all temperatures. 2. is non-spontaneous at all temperatures. 3.is spontaneous at high temperatures but non- spontaneous at low temperatures. 4.is spontaneous at low temperatures but non- spontaneous at high temperatures. 5.It is impossible to choose between the above responses without thermochemical data.

24 Below is some thermochemical data for diamond and graphite. True or false, equilibrium favors graphite in the above reaction. 1. True 2. False 3. The proportion of diamond and graphite are equal. 4. Cannot determine from the data given.

25 Below is some thermochemical data for diamond and graphite. True or false, equilibrium favors graphite in the above reaction. 1. True 2. False 3. The proportion of diamond and graphite are equal. 4. Cannot determine from the data given.

26 When  G = 0, 1. The equilibrium constant is The system has reached equilibrium. 3. The reaction will be too slow to observe. 4. All of the above are correct and 2 above are both correct. System free energy, G Reactants Products

27 When  G = 0, 1. The equilibrium constant is The system has reached equilibrium. 3. The reaction will be too slow to observe. 4. All of the above are correct and 2 above are both correct. System free energy, G Reactants (std state) Products (std state) Q>K Q=K Q

28 1.favors reactants at all temperatures. 2.favors products at all temperatures. 3.favors reactants high temperatures only 4.favors products at high temperatures only. 5.It is impossible to choose between the above responses without thermochemical data. The equilibrium constant for the decomposition of colorless dinitrogen tetroxide to form brown nitrogen dioxide

29 1.favors reactants at all temperatures. 2.favors products at all temperatures. 3.favors reactants high temperatures only 4.favors products at high temperatures only. 5.It is impossible to choose between the above responses without thermochemical data. The equilibrium constant for the decomposition of colorless dinitrogen tetroxide to form brown nitrogen dioxide

30 CO binds to iron in hemoglobin more favorably than does oxygen, which is why CO is poisonous. What is the free energy change for O 2 replacing CO bound to iron of hemoglobin? kJ mol kJ mol kJ mol kJ mol kJ mol -1

31 CO binds to iron in hemoglobin more favorably than does oxygen, which is why CO is poisonous. What is the free energy change for O 2 replacing CO bound to iron of hemoglobin? kJ mol kJ mol kJ mol kJ mol kJ mol -1

32 From The White Cliffs of Dover, England are made of chalk, CaCO 3, which obviously has a very low solubility, K sp is ~1 x at 298 K.  G o for the dissolution of CaCO 3 is: 1. ~ 70 kJ mol ~ 10 kJ mol ~ 1 kJ mol ~ -10 kJ mol ~ -70 kJ mol -1

33 From The White Cliffs of Dover, England are made of chalk, CaCO 3, which obviously has a very low solubility, K sp is ~1 x at 298 K.  G o for the dissolution of CaCO 3 is: 1. ~ 70 kJ mol ~ 10 kJ mol ~ 1 kJ mol ~ -10 kJ mol ~ -70 kJ mol -1


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