Ch.15 - Chemical Equilibrium
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- The equilibrium concentrations in a gas mixture at a particular temperature are 0.13 M H2, 0.70 M I2, and 2.1 M HI. What equilibrium concentrations are obtained at the same temperature when 0.20 mol of HI is injected into an empty 500.0-mL container?
Problem 1
- What is the equilibrium expression for the reaction of iron metal with water vapor? (LO 15.2 and 15.6) 2 Fe(s) + 3 H2O(g) ⇌ Fe2O3(s) + 3 H2(g)
Problem 2
- Given the data for the following reactions at 298 K: N2(g) + O2(g) ⇌ 2 NO(g) Kp = 4.4 * 10^-31 NO(g) + 1/2 O2(g) ⇌ NO2(g) Kp = 1.5 * 10^6, calculate the value of the equilibrium constant Kp at 298 K for the reaction N2(g) + 2 O2(g) ⇌ 2 NO2(g). (LO 15.3) (a) Kp = 6.6 * 10^-25 (b) Kp = 1.3 * 10^-24 (c) Kp = 9.9 * 10^-19 (d) Kp = 5.4 * 10^-28
Problem 3
- The reaction A21g2 + B21g2 ∆ 2 AB1g2 has an equilib- rium constant Kc = 9. The following figure represents a reaction mixture that contains A2 molecules (red), B2 mol- ecules (blue), and AB molecules. What statement about the mixture is true? (LO 15.5)
Problem 5
(a) The mixture is at equilibrium, and there will be no net shift in reaction direction. (b) The reaction will shift toward the reactants to reach equilibrium. (c) The reaction will shift toward the products to reach equilibrium. (d) More information is needed to answer this question.
- If Kc = 7.5 * 10^-9 at 1000 K for the reaction N2(g) + O2(g) ⇌ 2 NO(g), give the value of Kc at 1000 K for the reaction 2 N2(g) + 2 O2(g) ⇌ 4 NO(g)
Problem 6
- The gas-phase reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g) has an equilibrium constant Kc = 5.8 * 10^3 at 600 °C. A mixture contains [SO2] = 0.10 M, [O2] = 0.100 M, and [SO3] = 0.200 M. Which statement is true about the reaction direction and equilibrium mixture? (LO 15.8, 15.9) (a) The mixture is at equilibrium and contains appreciable amounts of reactants and products. (b) The reaction will shift to make more product, and the equilibrium mixture contains appreciable amounts of reactants and products. (c) The reaction will shift to make more reactants, and the equilibrium mixture contains mostly product. (d) The reaction will shift to make more product, and the equilibrium mixture contains mostly reactant.
Problem 7
- At a temperature of 430 °C, the reaction H2(g) + I2(g) ⇌ 2 HI(g) has an equilibrium constant Kc = 54.3. Suppose that a mixture of 0.500 mol of H2(g) and 0.500 mol of I2(g) is placed into a 1.00-L stainless-steel flask at 430 °C. Calculate the concentration of HI(g) when equilibrium is reached. (LO 15.10) (a) 0.393 M (b) 0.107 M (c) 0.500 M (d) 0.786 M
Problem 9
- Phosphorus pentachloride decomposes to phosphorus trichloride and chlorine at high temperatures according to the equation: PCl5(g) ⇌ PCl3(g) + Cl2(g). At 250 °C, 0.250 M PCl5 is added to the flask. If Kc = 1.80, what are the equilibrium concentrations of each gas? (LO 15.11) (a) [PCl5] = 0.028 M, [PCl3] = 0.222 M, and [Cl2] = 0.222 M (b) [PCl5] = 0.125 M, [PCl3] = 0.474 M, and [Cl2] = 0.474 M (c) [PCl5] = 1.80 M, [PCl3] = 1.80 M, and [Cl2] = 1.80 M (d) [PCl5] = 2.27 M, [PCl3] = 2.02 M, and [Cl2] = 2.02 M
Problem 11
- The decomposition of solid ammonium carbamate, (NH4)2NH2CO2, to gaseous ammonia and carbon dioxide is an endothermic reaction: (NH4)2NH2CO2(s) ⇌ 2 NH3(g) + CO2(g). (a) When solid (NH4)2NH2CO2 is introduced into an evacuated flask at 25 °C, the total pressure of gas at equilibrium is 0.116 atm. What is the value of Kp at 25 °C? (b) Given that the decomposition reaction is at equilibrium, how would the following changes affect the total quantity of NH3 in the flask once equilibrium is reestablished? (i) Adding CO2 (ii) Removing CO2 (iii) Adding (NH4)2NH2CO2 (iv) Increasing the total volume (v) Adding neon (vi) Increasing the temperature
Problem 15
Problem 15.64
Calculate the value of the equilibrium constant at 427 °C for the reaction
Na O1s2 + 1>2 O 1g2 ∆ Na O 1s2
given the following equilibrium constants at 427 °C.
Na2O1s2 ∆ 2 Na1l2 + 1>2 O21g2 Kc = 2 * 10-25 Na O 1s2 ∆ 2 Na1l2 + O 1g2 K = 5 * 10-29
Problem 15.65
Calculate the value of the equilibrium constant for the reaction 4 NH31g2 + 3 O21g2 ∆ 2 N21g2 + 6 H2O1g2
given the following equilibrium constants at a certain temperature.
2 H21g2 + O21g2 ∆ 2 H2O1g2 Kc = 3.2 * 1081
N21g2 + 3 H21g2 ∆ 2 NH31g2 Kc = 3.5 * 108
Problem 15.60a
If Kc = 7.5×10−9 at 1000 K for the reaction N2(g) + O2(g) → 2 NO(g), give the value of Kc at 1000 K for the reaction
(a) 2 NO(g) → N2(g) + O2(g)
Problem 15.63a
The reaction
2 PH31g2 + As21g2 ∆ 2 AsH31g2 + P21g2
has Kp = 2.9 * 10-5 at 873 K. At the same temperature,
what is Kp for each of the following reactions?
(a) 2 AsH31g2 + P21g2 ∆ 2 PH31g2 + As21g2
Problem 15.62b
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?
(b) 4 AsH31g2 ∆ 2 As21g2 + 6 H21g2
Problem 15.60b
If Kc = 7.5×10−9 at 1000 K for the reaction N2(g) + O2(g) → 2 NO(g), give the value of Kc at 1000 K for the reaction
(b) NO(g) → 1/2 N2(g) + 1/2 O2(g)
Problem 15.62c
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?
(c) 9 H21g2 + 3 As21g2 ∆ 6 AsH31g2
- Consider the interconversion of A molecules (red spheres) and B molecules (blue spheres) according to the reaction A ∆ B. Each of the series of pictures at the right represents a separate experiment in which time increases from left to right: (b) What is the value of the equilibrium constant Kc for the reaction A ∆ B?
Problem 41
- The reaction A2 + B ∆ A + AB has an equilibrium con-stant Kc = 2. The following pictures represent reaction mix- tures that contain A atoms (red), B atoms (blue), and A2 and AB molecules.
Problem 43
(a) Which reaction mixture is at equilibrium?
- Consider the reaction A + B ∆ AB. The vessel on the right contains an equilibrium mixture of A molecules (red spheres), B molecules (blue spheres), and AB molecules. If the stopcock is opened and the contents of the two vessels are allowed to mix, will the reaction go in the forward or reverse direction? Explain.
Problem 45
- The following pictures represent the composition of the equi- librium mixture for the reaction A + B ∆ AB at 300 K and at 400 K.
Problem 46
Is the reaction exothermic or endothermic? Explain using Le Châtelier's principle.
- The following pictures represent the initial and equilibrium states for the exothermic decomposition of gaseous A mol- ecules (red) to give gaseous B molecules (blue). (b) Will the number of A molecules in the equilibrium mix- ture increase, decrease, or remain the same after each of the following changes? Explain. (3) Increasing the pressure by adding an inert gas
Problem 50
Problem 50a
The following pictures represent the initial and equilibrium states for the exothermic decomposition of gaseous A mol- ecules (red) to give gaseous B molecules (blue). (a) Write a balanced chemical equation for the reaction.
- Identify the true statement about the rate of the forward and reverse reaction once a reaction has reached equilibrium. (a) The rate of the forward reaction and the reverse reaction is zero. (b) The rate of the forward reaction is greater than the rate of the reverse reaction. (c) The rate of the reverse reaction is greater than the rate of the forward reaction. (d) The rate of the forward reaction is equal to the rate of the reverse reaction.
Problem 52
- 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