Ch.19 - Free Energy & Thermodynamics

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Tro 6th Edition

Ch.19 - Free Energy & Thermodynamics

Problem 62

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 63

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 63a

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 63d

Problem 64a

Problem 64c

Problem 64d

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 65

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 66

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 67

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 69

Determine ΔG° for the reaction: Fe₂O₃(s) + 3 CO(g) → 2 Fe(s) + 3 CO₂(g) Use the following reactions with known ΔG°_rxnvalues:

2 Fe(s) + 3/2 O₂(g) → Fe₂O₃(s) ΔG°_rxn= -742.2 kJ

CO(g) + 12 O₂( g) → CO₂(g) ΔG°_rxn= -257.2 kJ

Problem 73

Consider the sublimation of iodine at 25.0 °C: I2(s) → I2(g). a. Find ΔG°rxn at 25.0 °C.

Problem 73b

Consider the sublimation of iodine at 25.0 °C : I₂(s) → I₂(g) b. Find ΔG°_rxnat 25.0 °C under the following nonstandard conditions: i. P_I2 = 1.00 mmHg ii. P_I2 = 0.100 mmHg

Problem 73c

Consider the sublimation of iodine at 25.0 °C : I₂(s) → I₂(g) c. Explain why iodine spontaneously sublimes in open air at 25.0 °C

Problem 74a

Consider the evaporation of methanol at 25.0 °C : CH₃OH(l) → CH₃OH(g) a. Find ΔG°_r at 25.0 °C.

Problem 74b

Consider the evaporation of methanol at 25.0 °C : CH₃OH(l) → CH₃OH(g) b. Find ΔG_r at 25.0 °C under the following nonstandard conditions: i. P_CH3OH = 150.0 mmHg ii. P_CH3OH= 100.0 mmHg iii. P_CH3OH = 10.0 mmHg

Problem 74c

Consider the evaporation of methanol at 25.0 °C : CH₃OH(l) → CH₃OH(g) c. Explain why methanol spontaneously evaporates in open air at 25.0 °C

Problem 76

Consider the reaction: CO₂(g) + CCl₄(g) ⇌ 2 COCl₂(g) Calculate ΔG for this reaction at 25 °C under the following conditions: i. P_CO2 = 0.112 atm ii. P_CCl4 = 0.174 atm iii. P_COCl2 = 0.744 atm

Problem 77a

Use data from Appendix IIB to calculate the equilibrium constants at 25 °C for each reaction. a. 2 CO(g) + O₂(g) ⇌ 2 CO₂(g)

Problem 77b

Use data from Appendix IIB to calculate the equilibrium constants at 25 °C for each reaction. b. 2 H₂S(g) ⇌ 2 H₂(g) + S₂(g)

Problem 78

Use data from Appendix IIB to calculate the equilibrium constants at 25 °C for each reaction. ΔG°f for BrCl(g) is -1.0 kJ/mol. a. 2 NO2(g) ⇌ N2O4(g) b. Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

Problem 79

Consider the reaction: CO(g) + 2 H2(g) ⇌ CH3OH(g) with Kp = 2.26 * 10^4 at 25°C. Calculate ΔG°rxn for the reaction at 25°C under each of the following conditions: a. standard conditions b. at equilibrium c. PCH3OH = 1.0 atm; PCO = PH2 = 0.010 atm

Problem 80a

Consider the reaction: I₂(g) + Cl₂(g) ⇌ 2 ICl(g) K_p = 81.9 at 25 °C Calculate ΔG_rxn for the reaction at 25 °C under each of the following conditions: a. standard conditions

Problem 80b

Consider the reaction: I₂(g) + Cl₂(g) ⇌ 2 ICl(g) K_p = 81.9 at 25 °C Calculate ΔG_rxn for the reaction at 25 °C under each of the following conditions: b. at equilibrium

Problem 80c

Consider the reaction: I₂(g) + Cl₂(g) ⇌ 2 ICl(g) K_p = 81.9 at 25 °C Calculate ΔG_rxnfor the reaction at 25 °C under each of the following conditions: c. P_ICl = 2.55 atm; P_I2 = 0.325 atm; P_Cl2 = 0.221 atm

Problem 81

Is the value of the equilibrium constant at 525 K for each reaction in Problem 73 estimated correctly?

Problem 82

Estimate the value of the equilibrium constant at 655 K for each reaction in Problem 74. (ΔHf° for BrCl is 14.6 kJ/mol.)

Problem 84

Consider the reaction: 2 NO(g) + O₂(g) ⇌ 2 NO₂(g) The following data show the equilibrium constant for this reaction measured at several different temperatures. Use the data to find ΔH°_rxnand ΔS°_rxnfor the reaction.

Problem 86

A reaction has an equilibrium constant of 8.5⨉10³ at 298 K. At 755 K, the equilibrium constant is 55.2. Find ΔH°rxn for the reaction.

Problem 87a

Determine the sign of ΔS_sys for each process. a. water boiling