McMurry - Chemistry 8th Edition - Chapter 18

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Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium

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McMurry 8th Edition

Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium

Problem 44
Predict the sign of the entropy change in the system for each of the following processes. (a) A solid sublimes. (b) A liquid freezes. (c) AgI precipitates from a solution containing Ag+ and I- ions. (d) Gaseous CO2 bubbles out of a carbonated beverage.
Problem 48
When rolling a pair of dice, there are two ways to get a point total of 3(1+2;2+1) but only one way to get a point total of 2(1+1). How many ways are there of getting point totals of 4 to 12? What is the most probable point total?
Problem 50
Consider the distribution of ideal gas molecules among three bulbs (A, B, and C) of equal volume. For each of the follow-ing states, determine the number of ways (W) that the state can be achieved, and use Boltzmann's equation to calculate the entropy of the state. (a) 2 molecules in bulb A (b) 2 molecules randomly distributed among bulbs A, B, and C
Problem 54
Which state has higher entropy? Explain in terms of probability. (a) A perfectly ordered crystal of solid nitrous oxide
or a disordered crystal in which the molecules are oriented randomly (b) Quartz glass (an amorphous solid) or a quartz crystal
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
Problem 58
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 60
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 68
State the second law of thermodynamics.
Problem 69
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 70
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 71
What are the values of x and y for the following reaction if E° = 0.91 V and ∆G° = -527 kJ?
Problem 72
Reduction of mercury(II) oxide with zinc gives metallic mercury: (b) Estimate at what temperature, if any, the reaction will become nonspontaneous
Problem 73
Elemental sulfur is formed by the reaction of zinc sulfide with oxygen: (b) At what temperature, if any, the reaction will become nonspontaneous?
Problem 77a
Phosphorus pentachloride forms from phosphorus trichloride and chlorine:
(a) Use data in Appendix B to calculate ∆S_sys, ∆S_surr, and ∆S_total 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, ∆H_vap = 30.7 kJ/mol and ∆S_vap = 87.0 J/(K*mol). Calculate ∆S_surr and ∆S_total at: (a) 70 °C
Problem 78d
For the vaporization of benzene, ∆H_vap = 30.7 kJ/mol and ∆S_vap = 87.0 J/(K*mol). Does benzene boil at 70 °C and 1 atm pressure? Calculate the normal boiling point of benzene.
Problem 79
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 81
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 82
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 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?
Problem 86
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 92
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 93
What is meant by the standard state of a substance?
Problem 98
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).