AP Chemistry – Ch16 Homework
Ch16 HW#1 p828 17,19,21,23,25,26
17. Which of the following processes are spontaneous?
a. Salt dissolves in H2O.
b. A clear solution becomes a uniform color after a few drops of dye are added.
c. Iron rusts.
d. You clean your bedroom. (If that’s even possible.)
19. Consider the following energy levels, each capable of holding 2 objects:
E = 2 kJ __
Draw all possible arrangements of the two identical particles in the
E = 1 kJ __
three energy levels. What total energy is most likely, that is, occurs
E = 0 kJ XX
the greatest number of times? Assume particles are indistinguishable from each other.
21. Choose the compound with the greatest positional entropy in each case.
a. 1 mol H2 (at STP) or 1 mol H2 (at 100˚C,0.5 atm)
b. 1 mol N2 (at STP) or 1 mol N2 (at 100K, 2 atm)
c. 1 mol H2O(s) (at 0˚C) or 1 mol H2O(l) (at 20˚C)
23. Which of the following involve an increase in the entropy of the system?
a. melting of a solid
b. sublimation
c. freezing
25. Predict the sign ∆Ssurr for the following processes.
a. H2O(l) → H2O(g)
b. CO2(g) → CO2(s)
26. Calculate ∆Ssurr for the following reactions at 25˚C and 1 atm.
a. C3H8(g) + 5O2(g) → 3CO2 (g) + 4H2O(l)
∆H˚= -2221 kJ
b. 2NO2(g) → 2NO(g) + O2(g)
∆H˚= 112 kJ
Ch16 HW#2 p829 27,28,29,31
27.Given the values of ∆H and ∆S which of the following changes will be spontaneous at constant T and P?
a. ∆H = +25 kJ, ∆S = +5.0 J/k, T = 300K
b. ∆H = + 25 kJ, ∆S = + 100 J/K T = 300K
c. ∆H = -10 kJ, ∆S = +5.0 J/K T= 298K
d. ∆H = -10 kJ , ∆S = -40 J/K T= 200K
28. At what temperatures will the following processes be spontaneous?
a. ∆H = -18kJ, ∆S = -60 J/K
b. ∆H = + 18 kJ, ∆S = + 60 J/K
c. ∆H = +18kJ, ∆S = -60 J/K
d. ∆H = -18 kJ , ∆S = 60 J/K
29. The boiling point of chloroform (CHCl3) is 61.7˚C. The enthalpy of vaporization is 31.4 kJ/mol.
Calculate the entropy of vaporization.
31. For ammonia (NH3), the enthalpy of fusion is 5.65 kJ/mol and the entropy of fusion is 28.9 J/K∙mol.
a. Will NH3 spontaneously melt at 200K?
b. What is the approximate melting point of ammonia?
Ch16 HW#3 p829 33,34,37,39
33. Predict the sign of ∆S˚ for each of the following changes.
b. AgCI(s) → Ag+ (aq) + CI-(aq)
c. 2H2(g) + O2(g) → 2H2O(l)
d. H2O(l) → H2O(g)
a.
34. Predict the sign of ∆S˚ for each of the following changes.
a. Na(s) + ½ CI2(g) → NaCI(s)
b. N2(g) + 3H2(g) → 2NH3(g)
c. NaCI(s) → Na+ (aq) + CI- (aq)
d. NaCI(s) → NaCI(l)
37. Predict the sign of ∆S˚, then calc ∆S˚ for each of the following reactions.
a. 2H2S(g) +SO2(g) → 3Srhombic(s) +2H2O(g) b. 2SO3 (g) → 2SO2(g) +O2(g)
c. Fe2O3(s) + 3H2(g) →2Fe(s) + 3H2O(g)
39. For the reaction
C2H2(g) + 4F2(g) → 2CF4(g) + H2(g) ∆S˚ is equal to -358 J/K.
Use this value and data from Appendix 4 to calculate the value of S˚ for CF4(g).
Ch16 HW#4 p830 45,47,49,53
45. From data in Appendix 4, calculate ∆H˚, ∆S˚, and ∆G˚ for each of the following reactions at 25˚C.
a. CH4(g) + 2O2(g) → CO2(g) +2H2O(g)
b. 6CO2(g) +6H2O(l) → C6H12O6(s) + 6O2(g)
c. P4O10(s) + 6H2O(l) → 4H3PO4(s)
d. HCl(g) + NH3(g) → NH4Cl(s)
47. From data in Appendix 4, calculate ∆H˚, ∆S˚, and ∆G˚ for each of the following reactions that produce acetic acid:
O
O
║
║
CH4(g) +CO2(g) → CH3C─OH(l)
CH3OH(g) + CO(g) → CH3C─OH(l)
Which reaction would you choose as a commercial method for producing acetic acid (CH3CO2H) at standard
conditions? What temperature conditions would you choose for the reaction?
Assume ∆H˚ and ∆S˚ do not depend on the temperature .
49. Given the following data: S(s) + 3/2 O2(g) → SO3(g)
∆G˚= -371 kJ
Calculate ∆G˚ for the reaction:
2SO2(g) +O2(g) → 2SO3(g)
∆G˚= -142 kJ
S(s) +O2(g) → SO2(g)
53. Use ∆G˚f values in Appendix 4 to calculate ∆G˚ for the reaction:
4PH3(g) +8O2 → P4O10(s) + 6H2O(l)
Ch16 HW#5 p830 46,48,50,52
46. For the reaction at 298 K
2NO2(g)  N2O4(g)
the values of ∆ H° and ΔS ° are – 58.03 kJ and – 176.6 j/K,
respectively. What is the value of ΔG° ? Assuming that ∆ H° and ΔS ° do not depend on temperature , at what
temperature is ΔG° = 0? Is ΔG° negative above or below this temperature?
48. Consider the two reactions for the production of ethanol: C2H4(g) + H2O(g)  CH3CH2OH(l)
C2H6(g) + H2O(g)  CH3CH2OH(l) + H2(g)
Which would be the more thermodynamically feasible at standard conditions? Why?
50. Given the following data : 2C6H6(l) + 15O2(g)  12CO2(g) + 6H2O(l) ∆G° = -6399kJ
Calculate the ∆G° for
C(s) + O2(g)  CO2(g)
∆G° = -394kJ
the reaction:
H2(g) + ½ O2(g)  H2O(l)
∆G° = -237kJ
6C(s) + 3H2  C6H6(l)
52. The value of ∆G° for the reaction 2C4H10(g) + 13O2(g)  8CO2 (g) + 10 H2O(l) is -5490 KJ.
Use this value and data from Appendix 4 to calculate the standard free energy of formation of C4H10(g).
Ch16 Rev p828 22,24,30,38b,44,54
22. Chose the substance with the greater positional entropy of the system?
a. 1 mol He (at 500°C, 1 atm) or 1 mol He (at 500°C, 2 atm)
b. 1 mol He (at STP) or 1 mol He (at 200K, 2 atm)
c. 1 mol He(s) (at 0 K) or 1 mol He(g) (at 5 K)
24. Which of the following involve an increase in the entropy of the system?
a. Mixing.
b. Separation.
c. Boiling.
30. For mercury, the enthalpy of vaporization is 58.51 kJ/mol and the entropy of vaporization is 92.92 J/K∙mol.
What is the normal boiling point of mercury?
38. Predict the sign of ∆S° and then calculate ∆S° for: N2(g) + 3H2(g) 2NH3(g)
44. Hydrogen cyanide is produced industrially by the following exothermic reaction:
2NH3(g) + 3O2(g) + 2CH4(g)
2HCN(g) + 6H2O(g)
Is the high temp needed for the thermodynamic or kinetic reasons?
54. Consider the reaction 2POCl3(g)  2PCl3(g) + O2(g)
a. Calculate ∆G° for this reaction. 2POCl3(g)  2PCl3(g) + O2(g)
The ∆Gf° values for POCl3(g) and PCl3(g) are -502 kJ/mol and -207. kJ/mol, respectively.
b. Is this reaction spontaneous under standard conditions at 298 K?
c. The value of ∆S° for this reaction is 179 J/K. At what temperatures is this reaction spontaneous at standard
conditions? Assume that ∆H° and ∆S° do not depend on temperature.