Tro - Chemistry: A Molecular Approach 4th Edition - Chapter 18

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Ch.18 - Free Energy and Thermodynamics

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Tro 4th Edition

Ch.18 - Free Energy and Thermodynamics

Problem 49
How does the molar entropy of a substance change with increasing temperature?
Problem 51
For each pair of substances, choose the one that you expect to have the higher standard molar entropy (S°) at 25 °C. Explain your choices. a. CO(g); CO₂(g) b. CH₃OH(l); CH₃OH(g) c. Ar(g); CO₂(g) d. CH₄(g); SiH₄(g) e. NO₂(g); CH₃CH₂CH₃(g) f. NaBr(s); NaBr(aq)
Problem 52
For each pair of substances, choose the one that you expect to have the higher standard molar entropy (S°) at 25 °C. Explain your choices. a. NaNO₃(s); NaNO₃(aq) b. CH₄(g); CH₃CH₃(g) c. Br₂(l); Br₂(g) d. Br₂(g); F₂(g) e. PCl₃(g); PCl₅(g) f. CH₃CH₂CH₂CH₃(g); SO₂(g)
Problem 53a,c
Rank each set of substances in order of increasing standard molar entropy (S°). Explain your reasoning. a. NH₃(g); Ne(g); SO₂(g); CH₃CH₂OH(g); He(g) c. CH₄(g); CF₄(g); CCl₄(g)
Problem 53b
Rank each set of substances in order of increasing standard molar entropy (S°). Explain your reasoning. b. H₂O(s); H₂O(l); H₂O(g)
Problem 54
Rank each set of substances in order of increasing standard molar entropy (S°). Explain your reasoning. a. I₂(g); F₂(g); Br₂(g); Cl₂(g) b. H₂O(g); H₂O₂(g); H₂S(g) c. C(s, graphite); C(s, diamond); C(s, amorphous)
Problem 55
Use data from Appendix IIB to calculate ΔSrxn ° for each of the reactions. In each case, try to rationalize the sign of ΔSrxn ° . a. C2H4(g) + H2(g) → C2H6(g)
Problem 55b
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. b. C(s) + H₂O(g) → CO(g) + H₂(g)
Problem 55c
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. c. CO(g) + H₂O(g) → H₂(g) + CO₂(g)
Problem 55d
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. d. 2 H₂S(g) + 3 O₂(g) → 2 H₂O(l) + 2 SO₂(g)
Problem 56a
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. a. 3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)
Problem 56b
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. b. Cr₂O₃(s) + 3 CO(g) → 2 Cr(s) + 3 CO₂(g)
Problem 56c
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. c. SO₂(g) + 1/2 O₂(g) → SO₃(g)
Problem 56d
Use data from Appendix IIB to calculate ΔS°_rxnfor each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. d. N₂O₄(g) + 4 H₂(g) → N₂(g) + 4 H₂O(g)
Problem 57
Find ΔS° for the formation of CH₂Cl₂(g) from its gaseous elements in their standard states. Rationalize the sign of ΔS°.
Problem 58
What is ΔS° for the reaction between nitrogen gas and fluorine gas to form nitrogen trifluoride gas, and how can the sign of ΔS° be rationalized?
Problem 59
Methanol (CH₃OH) burns in oxygen to form carbon dioxide and water. Write a balanced equation for the combustion of liquid methanol and calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C. Is the combustion of methanol spontaneous?
Problem 60
In photosynthesis, plants form glucose (C₆H₁₂O₆) and oxygen from carbon dioxide and water. Write a balanced equation for photosynthesis and calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C. Is photosynthesis spontaneous?
Problem 61
For each reaction, calculate ΔH°rxn, ΔS°rxn, and ΔG°rxn at 25 °C and state whether the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? b. NH4Cl(s) → HCl(g) + NH3(g) c. 3 H2(g) + Fe2O3(s) → 2 Fe(s) + 3 H2O(g)
Problem 61a
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? a. N₂O₄(g) → 2 NO₂(g)
Problem 61d
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? d. N₂(g) + 3 H₂(g) → 2 NH₃(g)
Problem 62
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxn at 25°C and determine whether the reaction is spontaneous. If the reaction is not spontaneous, could a change in temperature make it spontaneous? If so, should the temperature be increased or decreased from 25°C? b. 2 NH3(g) → N2H4(g) + H2(g)
Problem 62a
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? a. 2 CH₄(g) → C₂H₆(g) + H₂(g)
Problem 62c
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxnat 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? c. N₂(g) + O₂(g) → 2 NO(g)
Problem 62d
For each reaction, calculate ΔH°_rxn, ΔS°_rxn, and ΔG°_rxn at 25 °C and state whether or not the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25 °C? d. 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g)
Problem 63
Use standard free energies of formation to calculate ΔG° at 25 °C for each reaction in Problem 61. How do the values of ΔG° calculated this way compare to those calculated from ΔH° and ΔS°? Which of the two methods could be used to determine how ΔG° changes with temperature?
Problem 64
Using standard free energies of formation, calculate ΔG° at 25 °C for each reaction in Problem 62. How do the values of ΔG° calculated this way compare to those calculated from ΔH° and ΔS°? Which of the two methods can determine how ΔG° changes with temperature?
Problem 65
Is the question formulated correctly? If not, please correct it. Here is the question: 'Consider the reaction: 2 NO( g) + O2( g) → 2 NO2( g). Estimate ΔG° for this reaction at each temperature and predict whether or not the reaction is spontaneous, assuming that ΔH° and ΔS° do not change significantly within the given temperature range. a. 298 K b. 855 K.'
Problem 65b
Consider the reaction: 2 NO(g) + O₂(g) → 2 NO₂(g) Estimate ΔG° for this reaction at each temperature and predict whether or not the reaction is spontaneous. (Assume that ΔH° and ΔS° do not change too much within the given temperature range.) b. 715 K
Problem 66
Consider the reaction: CaCO3(s) → CaO(s) + CO2(g). Estimate ΔG° for this reaction at each temperature and predict whether or not the reaction is spontaneous. (Assume that ΔH° and ΔS° do not change too much within the given temperature range.) a. 298 K b. 1055 K c. 1455 K.