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Problem 56a
Which state in each of the following pairs has the higher entropy per mole of substance? (a) H2 at 25 °C in a volume of 10 L or H2 at 25 °C in a volume of 50 L
Problem 56d
Which state in each of the following pairs has the higher entropy per mole of substance? (d) CO2 at STP or CO2 at 100 °C and 0.1 atm
Problem 57a
Which state in each of the following pairs has the higher entropy per mole of substance? (a) Ice at -40 °C or ice at 0 °C
Problem 57b
Which state in each of the following pairs has the higher entropy per mole of substance? (b) N2 at STP or N2 at 0 °C and 10 atm
Problem 57d
Which state in each of the following pairs has the higher entropy per mole of substance? (d) Water vapor at 150 °C and 1 atm or water vapor at 100 °C and 2 atm
- What is the entropy change when the volume of 1.6 g of O2 increases from 2.5 L to 3.5 L at a constant temperature of 75 °C? Assume that O2 behaves as an ideal gas.
Problem 58
- Make a rough, qualitative plot of the standard molar entropy versus temperature for methane from 0 K to 298 K. Incorporate the following data into your plot: mp = -182 °C; bp = -164 °C; °S = 186.2 J/(K*mol) at 25 °C.
Problem 60
- State the second law of thermodynamics.
Problem 68
- An isolated system is one that exchanges neither matter nor energy with the surroundings. What is the entropy criterion for spontaneous change in an isolated system? Give an example of a spontaneous process in an isolated system.
Problem 69
- Give an equation that relates the entropy change in the surroundings to the enthalpy change in the system. What is the sign of ∆Ssurr for the following? (a) An exothermic reaction (b) An endothermic reaction
Problem 70
- What are the values of x and y for the following reaction if E° = 0.91 V and ∆G° = -527 kJ?
Problem 71
- Reduction of mercury(II) oxide with zinc gives metallic mercury: (b) Estimate at what temperature, if any, the reaction will become nonspontaneous
Problem 72
- Elemental sulfur is formed by the reaction of zinc sulfide with oxygen: (b) At what temperature, if any, the reaction will become nonspontaneous?
Problem 73
Problem 77a
Phosphorus pentachloride forms from phosphorus trichloride and chlorine:
(a) Use data in Appendix B to calculate ∆Ssys, ∆Ssurr, and ∆Stotal for this reaction. Is the reaction spontaneous under standard-state conditions at 25 °C?
Problem 77b
Phosphorus pentachloride forms from phosphorus trichloride and chlorine: PCl3(g) + Cl2(g) → PCl5(g) (b) Estimate the temperature at which the reaction will become nonspontaneous.
Problem 78a
For the vaporization of benzene, ∆Hvap = 30.7 kJ/mol and ∆Svap = 87.0 J/(K*mol). Calculate ∆Ssurr and ∆Stotal at: (a) 70 °C
Problem 78d
For the vaporization of benzene, ∆Hvap = 30.7 kJ/mol and ∆Svap = 87.0 J/(K*mol). Does benzene boil at 70 °C and 1 atm pressure? Calculate the normal boiling point of benzene.
- For the melting point of sodium chloride, ΔHfusion = 28.16 kJ/mol and ΔSfusion = 26.22 J/(K·mol). Does NaCl melt at 1100 K? Calculate the melting point of NaCl.
Problem 79
- The entropy change for a certain nonspontaneous reaction at 50 °C is 104 J/K. (a) Is the reaction endothermic or exothermic? (b) What is the minimum value of ∆H (in kJ) for the reaction?
Problem 81
- Identify the true statement. A spontaneous reaction must have (a) a negative enthalpy change. (b) a positive enthalpy change. (c) a positive entropy change. (d) a positive free-energy change. (e) a negative free-energy change.
Problem 82
Problem 85a
Consider a twofold expansion of 1 mol of an ideal gas at 25 °C in the isolated system shown in Figure 18.1. (a) What are the values of ∆H, ∆S, and ∆G for the process?
Problem 85b
Consider a twofold expansion of 1 mol of an ideal gas at 25 °C in the isolated system shown in Figure 18.1. (b) How does this process illustrate the second law of thermodynamics?
- Given the data in Problem 18.78, calculate ∆G for the vaporization of benzene at: (a) 70 °C Predict whether benzene will boil at each of these temperatures and 1 atm pressure.
Problem 86
- Define (a) the standard free-energy change, ∆G°, for a reaction, and (b) the standard free energy of formation, ∆G°f, of a substance.
Problem 92
Problem 93
What is meant by the standard state of a substance?
- Use the data in Appendix B to tell which of the following compounds are thermodynamically stable with respect to their constituent elements at 25 °C: (a) BaCO3(s) (b) HBr(g) (c) N2O(g) (d) C2H4(g).
Problem 98
- Use the data in Appendix B to determine which of the following compounds are thermodynamically stable with respect to their constituent elements at 25 °C.
Problem 99
(a) C6H6(l) (b) NO(g) (c) PH3(g) (d) FeO(s) - Use the values of of ∆G°f in Appendix B to calculate the stan-dard free-energy change for the synthesis of dichloroethane from ethylene and chlorine: C2H41g2 + Cl21g2S CH2ClCH2Cl1l2 Is it possible to synthesize dichloroethane from gaseous C2H4 and Cl2, each at 25 °C and 1 atm pressure?
Problem 100
- Ethanol is manufactured in industry by the hydration of ethylene: Using the data in Appendix B, calculate ∆G° and show that this reaction is spontaneous at 25 °C. Why does this reaction become nonspontaneous at higher temperatures? Estimate the temperature at which the reaction becomes nonspontaneous.
Problem 102
- Consider the conversion of 1,2-dichloroethane to vinyl chloride, the starting material for manufacturing poly(vinyl chloride) (PVC) plastics: Is this reaction spontaneous under standard-state conditions? Would it help to carry out the reaction in the presence of base to remove HCl? Explain. Is it possible to synthesize vinyl chlo-ride from graphite, gaseous H2, and gaseous Cl2 at 25 °C and 1 atm pressure?
Problem 105