Ch.15 - Chemical Equilibrium
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- Identify the true statement about the concentrations of A and B once the reaction A ⇌ B has reached equilibrium. (a) The concentration of A equals the concentration of B. (b) The concentrations of A and B are constant. (c) The concentration of A decreases and the concentration of B increases. (d) The concentration of B decreases and the concentration of A increases.
Problem 53
- For each of the following equilibria, write the equilibrium constant expression for Kc. (a) CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) (b) 3 F2(g) + Cl2(g) ⇌ 2 ClF3(g) (c) H2(g) + F2(g) ⇌ 2 HF(g)
Problem 56
- For each of the following equilibria, write the equilibrium constant expression for Kc. (a) 2 C2H4(g) + O2(g) ⇌ 2 CH3CHO(g) (b) CO(g) + H2O(g) ⇌ CO2(g) + H2(g) (c) 4 NH3(g) + 5 O2(g) ⇌ 4 NO(g) + 6 H2O(g)
Problem 57
- For each of the equilibria in Problem 15.56, write the equi-librium constant expression for Kp and give the equation that relates Kp and Kc. (a)
Problem 58
- For each of the equilibria in Problem 15.57, write the equilibrium constant expression for Kp and give the equation that relates Kp and Kc for parts (a), (b), and (c).
Problem 59
Problem 62a
The reaction 2 AsH31g2 ∆ As21g2 + 3 H21g2 has Kp = 7.2 * 107 at 1073 K. At the same temperature, what is Kp for each of the following reactions? (a) As21g2 + 3 H21g2 ∆ 2 AsH31g2
- The vapor pressure of water at 25 °C is 0.0313 atm. Cal- culate the values of Kp and Kc at 25 °C for the equilibrium H2O1l2 ∆ H2O1g2.
Problem 70
- Chlorine monoxide and dichlorine dioxide are involved in the catalytic destruction of stratospheric ozone. They are related by the equation 2 ClO(g) ⇌ Cl2O2(g) for which Kc is 4.96 * 10^11 at 253 K. For an equilibrium mixture in which [Cl2O2] is 6.00 * 10^-6 M, what is [ClO]?
Problem 72
- Sulfur dioxide reacts with oxygen in a step in the production of sulfuric acid. 2 SO2(g) + O2(g) ⇌ 2 SO3(g) Kc = 7.9 * 10^4 at 1800 K. For an equilibrium mixture in which [SO2] = 1.5 * 10^-3 M and [O2] = 3.0 * 10^-3 M, what is [SO3]?
Problem 73
- For each of the following equilibria, write the equilibrium constant expression for Kc. Where appropriate, also write the equilibrium constant expression for Kp. (a) Fe2O31s2 + 3 CO1g2 ∆ 2 Fe1l2 + 3 CO21g2
Problem 74
- For each of the following equilibria, write the equilibrium constant expression for Kc. Where appropriate, also write the equilibrium constant expression for Kp. (a) WO3(s) + 3 H2(g) ⇌ W(s) + 3 H2O(g) (b) Ag+(aq) + Cl-(aq) ⇌ AgCl(s) (c) 2 FeCl3(s) + 3 H2O(g) ⇌ Fe2O3(s) + 6 HCl(g) (d) MgCO3(s) ⇌ MgO(s) + CO2(g)
Problem 75
- Which of the following reactions yield appreciable equilib- rium concentrations of both reactants and products? (a) 2 Cu1s2 + O21g2 ∆ 2 CuO1s2; Kc = 4 * 1045
Problem 77
- The value of Kc for the reaction 3 O21g2 ∆ 2 O31g2 is 1.7 * 10-56 at 25°C. Do you expect pure air at 25 °C to contain much O3 (ozone) when O2 and O3 are in equilib- rium? If the equilibrium concentration of O2 in air at 25 °C is 8 * 10-3 M, what is the equilibrium concentration of O3?
Problem 79
- Phosphine (PH3) decomposes at elevated temperatures, yielding gaseous P2 and H2: 2 PH3(g) ⇌ P2(g) + 3 H2(g), Kp = 398 at 873 K. (b) When a mixture of PH3, P2, and H2 comes to equilibrium at 873 K, P_P2 = 0.412 atm and P_H2 = 0.822 atm. What is P_PH3?
Problem 82
- At 500 K, the equilibrium constant for the dissociation reaction H2(g) ⇌ 2H(g) is very small (Kc = 1.2 × 10⁻⁴²). (a) What is the molar concentration of H atoms at equilibrium if the equilibrium concentration of H2 is 0.10 M? (b) How many H atoms and H2 molecules are present in 1.0 L of 0.10 M H2 at 500 K?
Problem 83
- Calculate the equilibrium concentrations of N2O4 and NO2 at 25 °C in a vessel that contains an initial N2O4 concentration of 0.0500 M. The equilibrium constant Kc for the reaction N2O4(g) ⇌ 2 NO2(g) is 4.64 × 10⁻³ at 25 °C.
Problem 84
- Calculate the equilibrium concentrations at 25 °C for the reaction in Problem 15.84 if the initial concentrations are 3N2O44 = 0.0200 M and 3NO24 = 0.0300 M.
Problem 85
- A sample of HI 19.30 * 10^-3 mol^2 was placed in an empty 2.00-L container at 1000 K. After equilibrium was reached, the concentration of I2 was 6.29 * 10^-4 M. Calculate the value of Kc at 1000 K for the reaction H2(g) + I2(g) ⇌ 2 HI(g).
Problem 86
- The industrial solvent ethyl acetate is produced by the reac-tion of acetic acid with ethanol: CH3CO2H1soln2 + CH3CH2OH1soln2 ∆ CH3CO2CH2CH31soln2 + H2O1soln2 Ethyl acetate (b) A solution prepared by mixing 1.00 mol of acetic acid and 1.00 mol of ethanol contains 0.65 mol of ethyl ace- tate at equilibrium. Calculate the value of Kc. Explain why you can calculate K without knowing the volume of the solution.
Problem 87
- A characteristic reaction of ethyl acetate is hydrolysis, the reverse of the reaction in Problem 15.87. Write the equilibrium equation for the hydrolysis of ethyl acetate, and use the data in Problem 15.87 to calculate Kc for the hydrolysis reaction.
Problem 88
- Gaseous indium dihydride is formed from the elements at elevated temperature: ln(g) + H2(g) ightarrow lnH2(g), Kp = 1.48 at 973 K. Partial pressures measured in a reaction vessel are: P_in = 0.0600 atm, P_H2 = 0.0350 atm, P_lnH2 = 0.0760 atm. (b) Determine the equilibrium partial pressures of all the gases.
Problem 89
- The following reaction, which has Kc = 0.145 at 298 K, takes place in carbon tetrachloride solution: 2 BrCl1soln2 ∆ Br21soln2 + Cl21soln2 A measurement of the concentrations shows 3BrCl4 = 0.050 M, 3Br24 = 0.035 M, and 3Cl24 = 0.030 M. (b) Determine the equilibrium concentrations of BrCl, Br1, and Cl2.
Problem 90
- An equilibrium mixture of N2, H2, and NH3 at 700 K con- tains 0.036 M N2 and 0.15 M H2. At this temperature, Kc for the reaction N21g2 + 3 H21g2 ∆ 2 NH31g2 is 0.29. What is the concentration of NH3?
Problem 91
- An equilibrium mixture of O2, SO2, and SO3 contains equal concentrations of SO2 and SO3. Calculate the concentration of O2 if Kc = 2.7 * 10^2 for the reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g).
Problem 92
- The air pollutant NO is produced in automobile engines from the high-temperature reaction N2(g) + O2(g) ⇌ 2 NO(g); Kc = 1.7 * 10^-3 at 2300 K. If the initial concentrations of N2 and O2 at 2300 K are both 1.40 M, what are the concentrations of NO, N2, and O2 when the reaction mixture reaches equilibrium?
Problem 93
- Recalculate the equilibrium concentrations in Problem 15.93 if the initial concentrations are 2.24 M N2 and 0.56 M O2. (This N2>O2 concentration ratio is the ratio found in air.)
Problem 94
- The interconversion of l-___-lysine and l-b-lysine, for which Kc = 7.20 at 333 K, is catalyzed by the enzyme lysine 2,3-aminomutase. Lysine occurs in proteins while l-b-lysine is a precursor to certain antibiotics. At 333 K, a solution of l-___-lysine at a concentration of 3.00 * 10^-3 M is placed in contact with lysine 2,3-aminomutase. What are the equilibrium concentrations of l-___-lysine and l-b-lysine?
Problem 95
- The value of Kc for the reaction of acetic acid with ethanol is 3.4 at 25°C: CH3CO2H1soln2 + CH3CH2OH1soln2 ∆ Acetic acid Ethanol CH3CO2CH2CH31soln2 + H2O1soln2 Kc = 3.4 (a) How many moles of ethyl acetate are present in an equi- librium mixture that contains 4.0 mol of acetic acid, 6.0 mol of ethanol, and 12.0 mol of water at 25 °C?
Problem 96
- In a basic aqueous solution, chloromethane undergoes a substitution reaction in which Cl- is replaced by OH-: CH3Cl(aq) + OH-(aq) ⇌ CH3OH(aq) + Cl-(aq). The equilibrium constant Kc is 1 * 10^16. Calculate the equilibrium concentrations of CH3Cl, CH3OH, OH-, and Cl- in a solution prepared by mixing equal volumes of 0.1 M CH3Cl and 0.2 M NaOH. (Hint: In defining x, assume that the reaction goes 100% to completion, and then take account of a small amount of the reverse reaction.)
Problem 97
- At 700 K, Kp = 0.140 for the reaction ClF₃(g) ⇌ ClF(g) + F₂(g). Calculate the equilibrium partial pressures of ClF₃, ClF, and F₂ if only ClF₃ is present initially, at a partial pressure of 1.47 atm.
Problem 98