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Problem 76a
Consider the reaction: I2(g) + Cl2(g) ⇌ 2 ICl(g) Kp = 81.9 at 25 °C Calculate ΔGrxn for the reaction at 25 °C under each of the following conditions: a. standard conditions
Problem 76b
Consider the reaction: I2(g) + Cl2(g) ⇌ 2 ICl(g) Kp = 81.9 at 25 °C Calculate ΔGrxn for the reaction at 25 °C under each of the following conditions: b. at equilibrium
Problem 76c
Consider the reaction: I2(g) + Cl2(g) ⇌ 2 ICl(g) Kp = 81.9 at 25 °C Calculate ΔGrxn for the reaction at 25 °C under each of the following conditions: c. PICl = 2.55 atm; PI2 = 0.325 atm; PCl2 = 0.221 atm
- Is the value of the equilibrium constant at 525 K for each reaction in Problem 73 estimated correctly?
Problem 77
- 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 78
Problem 80
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°rxn and ΔS°rxn for the reaction.
Problem 82
A reaction has an equilibrium constant of 8.5⨉103 at 298 K. At 755 K, the equilibrium constant is 0.65. Find ΔH°rxn for the reaction.
Problem 83a
Determine the sign of ΔSsys for each process. a. water boiling
Problem 83b
Determine the sign of ΔSsys for each process. b. water freezing
- Our atmosphere is composed primarily of nitrogen and oxygen, which coexist at 25 °C without reacting to any significant extent. However, the two gases can react to form nitrogen monoxide according to the reaction: N2(g) + O2(g) → 2 NO(g). a. Calculate ΔG° and Kp for this reaction at 298 K. Is the reaction spontaneous? b. Estimate ΔG° at 2000 K. Does the reaction become more spontaneous as temperature increases?
Problem 85
Problem 86
Nitrogen dioxide, a pollutant in the atmosphere, can combine with water to form nitric acid. One of the possible reactions is shown here. Calculate ΔG° and Kp for this reaction at 25 °C and comment on the spontaneity of the reaction. 3 NO2(g) + H2O(l)→ 2 HNO3(aq) + NO(g)
Problem 87
Ethene (C2H4) can be halogenated by the reaction: C2H4(g) + X2(g) → C2H4X2(g) where X2 can be Cl2, Br2, or I2. Use the thermodynamic data given to calculate ΔH°, ΔS°, ΔG°, and Kp for the halogenation reaction by each of the three halogens at 25 °C. Which reaction is most spontaneous? Least spontaneous? What is the main factor responsible for the difference in the spontaneity of the three reactions? Does higher temperature make the reactions more spontaneous or less spontaneous?
Compound ΔH°f (kJ/mol) S° (J/mol·K)
C2H4Cl2(g) -129.7 308.0
C2H4Br2(g) +38.3 330.6
C2H4I2(g) +66.5 347.8
Problem 88
H2 reacts with the halogens (X2) according to the reaction: H2(g) + X2(g) → 2 HX(g) where X2 can be Cl2, Br2, or I2. Use the thermodynamic data in Appendix IIB to calculate ΔH°, ΔS°, ΔG°, and Kp for the reaction between hydrogen and each of the three halogens. Which reaction is most spontaneous? Least spontaneous? What is the main factor responsible for the difference in the spontaneity of the three reactions? Does higher temperature make the reactions more spontaneous or less spontaneous?
Problem 89a
Consider this reaction occurring at 298 K: N2O(g) + NO2(g) ⇌ 3 NO(g) a. Show that the reaction is not spontaneous under standard conditions by calculating ΔG°rxn.
Problem 89b
Consider this reaction occurring at 298 K: N2O(g) + NO2(g) ⇌ 3 NO(g) b. If a reaction mixture contains only N2O and NO2 at partial pressures of 1.0 atm each, the reaction will be spontaneous until some NO forms in the mixture. What maximum partial pressure of NO builds up before the reaction ceases to be spontaneous?
Problem 89c
Consider this reaction occurring at 298 K: N2O(g) + NO2(g) ⇌ 3 NO(g) c. Can the reaction be made more spontaneous by an increase or decrease in temperature? If so, what temperature is required to make the reaction spontaneous under standard conditions?
Problem 90a
Consider this reaction occurring at 298 K: BaCO3(s) ⇌ BaO(s) + CO2(g) a. Show that the reaction is not spontaneous under standard conditions by calculating ΔG°rxn.
Problem 90b
Consider this reaction occurring at 298 K: BaCO3(s) ⇌ BaO(s) + CO2( g) b. If BaCO3 is placed in an evacuated flask, what is the partial pressure of CO2 when the reaction reaches equilibrium?
Problem 90c
Consider this reaction occurring at 298 K: BaCO3(s) ⇌ BaO(s) + CO2(g) c. Can the reaction be made more spontaneous by an increase or decrease in temperature? If so, at what temperature is the partial pressure of carbon dioxide 1.0 atm?
Problem 91a
Living organisms use energy from the metabolism of food to create an energy-rich molecule called adenosine triphosphate (ATP). The ATP acts as an energy source for a variety of reactions that the living organism must carry out to survive. ATP provides energy through its hydrolysis, which can be symbolized as follows: ATP(aq) + H2O(l) → ADP(aq) + Pi(aq) ΔGrxn ° = -30.5 kJ where ADP represents adenosine diphosphate and Pi represents an inorganic phosphate group (such as HPO42-). a. Calculate the equilibrium constant, K, for the given reaction at 298 K.
Problem 91b
Living organisms use energy from the metabolism of food to create an energy-rich molecule called adenosine triphosphate (ATP). The ATP acts as an energy source for a variety of reactions that the living organism must carry out to survive. ATP provides energy through its hydrolysis, which can be symbolized as follows: ATP(aq) + H2O(l) → ADP(aq) + Pi(aq) ΔG°rxn = -30.5 kJ where ADP represents adenosine diphosphate and Pi represents an inorganic phosphate group (such as HPO42-). b. The free energy obtained from the oxidation (reaction with oxygen) of glucose (C6H12O6) to form carbon dioxide and water can be used to re-form ATP by driving the given reaction in reverse. Calculate the standard free energy change for the oxidation of glucose and estimate the maximum number of moles of ATP that can be formed by the oxidation of one mole of glucose.
- The standard free energy change for the hydrolysis of ATP was given in Problem 91. In a particular cell, the concentrations of ATP, ADP, and Pi are 0.0031 M, 0.0014 M, and 0.0048 M, respectively. Calculate the free energy change for the hydrolysis of ATP under these conditions, assuming a temperature of 298 K.
Problem 92
Problem 93b
These reactions are important in catalytic converters in automobiles. Calculate ΔG° for each at 298 K. Predict the effect of increasing temperature on the magnitude of ΔG°.
a. 2 CO(g) + 2 NO(g) → N2(g) + 2 CO2(g)
b. 5 H2(g) + 2 NO(g) → 2 NH3(g) + 2 H2O(g)
c. 2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g)
d. 2 NH3(g) + 2 O2(g) → N2O(g) + 3 H2O(g)
Problem 94b
Calculate ΔG° at 298 K for these reactions and predict the effect on ΔG° of lowering the temperature.
a. NH3(g) + HBr(g) → NH4Br(s)
b. CaCO3(s) → CaO(s) + CO2(g)
c. CH4(g) + 3 Cl2(g) → CHCl3(g) + 3 HCl(g) (ΔG°f for CHCl3(g) is -70.4 kJ/mol.)
Problem 95
All the oxides of nitrogen have positive values of ΔG°f at 298 K, but only one common oxide of nitrogen has a positive ΔS°f. Identify that oxide of nitrogen without reference to thermodynamic data and explain.
Problem 96
The values of ΔG°f for the hydrogen halides become less negative with increasing atomic number. The ΔG°f of HI is slightly positive. However, the trend in ΔS°f is to become more positive with increasing atomic number. Explain.
Problem 97
Consider the reaction X2(g) → 2X(g). When a vessel initially containing 755 torr of X2 comes to equilibrium at 298 K, the equilibrium partial pressure of X is 103 torr. The same reaction is repeated with an initial partial pressure of 748 torr of X2 at 755 K; the equilibrium partial pressure of X is 532 torr. Find ΔH° for the reaction.
- Is the sign of ΔSuniv for each process positive or negative? Explain for the following: b. the electrolysis of H2O(l) to H2(g) and O2(g) at 298 K c. the growth of an oak tree from a little acorn.
Problem 99
Problem 99a
Indicate and explain the sign of ΔSuniv for each process. a. 2 H2(g) + O2(g) → 2 H2O (l) at 298 K.
Problem 101
A metal salt with the formula MCl2 crystallizes from water to form a solid with the composition MCl2 • 6 H2O. The equilibrium vapor pressure of water above this solid at 298 K is 18.3 mmHg. What is the value of ΔG for the reaction MCl2 • 6 H2O(s) ⇌ MCl2(s) + 6 H2O(g) when the pressure of water vapor is 18.3 mmHg? When the pressure of water vapor is 760 mmHg?