Ch.15 - Chemical Equilibrium
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- The reaction of iron(III) oxide with carbon monoxide is important in making steel. At 1200 K, Kp = 19.9 for the reaction Fe2O3(s) + 3 CO(g) ⇌ 2 Fe(l) + 3 CO2(g). What are the equilibrium partial pressures of CO and CO2 if CO is the only gas present initially, at a partial pressure of 0.978 atm?
Problem 99
- A 5.00-L reaction vessel is filled with 1.00 mol of H2, 1.00 mol of I2, and 2.50 mol of HI. Calculate the equilibrium concentrations of H2, I2, and HI at 500 K. The equilibrium constant Kc at 500 K for the reaction H2(g) + I2(g) ⇌ 2 HI(g) is 129.
Problem 101
- At 1000 K, the value of Kc for the reaction C1s2 + H2O1g2 ∆ CO1g2 + H21g2 is 3.0 * 10-2. Calculate the equilibrium concentrations of H2O, CO2, and H2 in a reac- tion mixture obtained by heating 6.00 mol of steam and an excess of solid carbon in a 5.00-L container. What is the molar composition of the equilibrium mixture?
Problem 102
- When 1.000 mol of PCl5 is introduced into a 5.000-L container at 500 K, 78.50% of the PCl5 dissociates to give an equilibrium mixture of PCl5, PCl3, and Cl2: PCl5(g) ⇌ PCl3(g) + Cl2(g). (a) Calculate the values of Kc and Kp.
Problem 103
- 15.104 Consider the reaction C(s) + CO2(g) ⇌ 2 CO(g). When 1.50 mol of CO2 and an excess of solid carbon are heated in a 20.0-L container at 1100 K, the equilibrium concentration of CO is 7.00 x 10^-2 M. (a) What is the equilibrium concentration of CO2? (b) What is the value of the equilibrium constant Kc at 1100 K?
Problem 104
- The equilibrium constant Kp for the gas-phase thermal decomposition of tert-butyl chloride is 3.45 at 500 K: CH3C(CH3)2Cl(g) ↔ CH2=C(CH3)2(g) + HCl(g). (b) Calculate the molar concentrations of reactants and products in an equilibrium mixture obtained by heating 1.00 mol of tert-butyl chloride in a 5.00-L vessel at 500 K. (c) A mixture of isobutylene (0.400 atm partial pressure at 500 K) and HCl (0.600 atm partial pressure at 500 K) is allowed to reach equilibrium at 500 K. What are the equilibrium partial pressures of tert-butyl chloride, isobutylene, and HCl?
Problem 105
- At 100 °C, Kc = 4.72 for the reaction 2 NO21g2 ∆ N2O41g2. An empty 10.0-L flask is filled with 4.60 g of NO2 at 100 °C. What is the total pressure in the flask at equilibrium?
Problem 106
- At 25 °C, Kc = 216 for the reaction 2 NO2(g) ⇌ N2O4(g). A 1.00-L flask containing a mixture of NO2 and N2O4 at 25 °C has a total pressure of 1.50 atm. What is the partial pressure of each gas?
Problem 107
- At 500 °C, F2 gas is stable and does not dissociate, but at 840 °C, some dissociation occurs: F2(g) ⇌ 2 F(g). A flask filled with 0.600 atm of F2 at 500 °C was heated to 840 °C, and the pressure at equilibrium was measured to be 0.984 atm. What is the equilibrium constant Kp for the dissociation of F2 gas at 840 °C?
Problem 108
- The reaction NO(g) + NO2(g) ⇌ N2O3(g) takes place in the atmosphere with Kc = 13 at 298 K. A gas mixture is prepared with 2.0 mol NO and 3.0 mol NO2 and an initial total pressure of 1.65 atm. (a) What are the equilibrium partial pressures of NO, NO2, and N2O3 at 298 K?
Problem 109
- The equilibrium constant Kc for the reaction N21g2 + 3 H21g2 ∆ 2 NH31g2 is 4.20 at 600 K. When a quantity of gaseous NH3 was placed in a 1.00-L reaction vessel at 600 K and the reaction was allowed to reach equilibrium, the vessel was found to contain 0.200 mol of N2. How many moles of NH3 were placed in the vessel?
Problem 111
- At 45 °C, Kc = 0.619 for the reaction N2O4(g) ⇌ 2 NO2(g). If 46.0 g of N2O4 is introduced into an empty 2.00-L container, what are the partial pressures of NO2 and N2O4 after equilibrium has been achieved at 45 °C?
Problem 112
- When 9.25 g of ClF3 was introduced into an empty 2.00-L container at 700.0 K, 19.8% of the ClF3 decomposed to give an equilibrium mixture of ClF3, ClF, and F2. ClF3 (g) ⇌ ClF (g) + F2 (g). (a) What is the value of the equilibrium constant Kc at 700.0 K? (b) What is the value of the equilibrium constant Kp at 700.0 K? (c) In a separate experiment, 39.4 g of ClF3 was introduced into an empty 2.00-L container at 700.0 K. What are the concentrations of ClF3, ClF, and F2 when the mixture reaches equilibrium?
Problem 113
- The reaction of fumarate with water to form L-malate is catalyzed by the enzyme fumarase; Kc = 3.3 at 37°C. When a reaction mixture with [fumarate] = 1.56 * 10-3 M and [l -malate] = 2.27 * 10-3 M comes to equilibrium in the presence of fumarase at 37 °C, what are the equilibrium concentrations of fumarate and L-malate? (Water can be omit- ted from the equilibrium equation because its concentration in dilute solutions is essentially the same as that in pure water.)
Problem 115
- Calculate the equilibrium concentrations of SO2, Cl2, and SO2Cl2 at 298 K if the initial concentrations are [SO2] = 1.50 M and [Cl2] = 0.85 M. The equilibrium constant Kc for the reaction SO2(g) + Cl2(g) ⇌ SO2Cl2(g) is 8.40 × 10^-3 at 298 K.
Problem 116
- Calculate the equilibrium concentrations of H2O(g), Cl2(g), HCl(g), and O2(g) at 298 K if the initial concentrations are [H2O] = 0.050 M and [Cl2] = 0.100 M. The equilibrium constant Kc for the reaction H2O(g) + Cl2(g) ⇌ 2 HCl(g) + O2(g) is 8.96 × 10^-9 at 298 K.
Problem 117
Problem 118a,b
Consider the following equilibrium: Ag+ (aq) + Cl-(aq) → AgCl(s) Use Le Châtelier's principle to predict how the amount of solid silver chloride will change when the equilibrium is disturbed by: (a) Adding NaCl (b) Adding AgNO3
Problem 118c
Consider the following equilibrium: Ag+ (aq) + Cl-(aq) → AgCl(s) Use Le Châtelier's principle to predict how the amount of solid silver chloride will change when the equilibrium is disturbed by: (c) Adding NO3, which reacts with Ag+ to form the complex ion Ag(NH3)2+
Problem 118d
Consider the following equilibrium: Ag+(aq) + Cl-(aq) ⇌ AgCl(s) Use Le Châtelier's principle to predict how the amount of solid silver chloride will change when the equilibrium is disturbed by: (d) Removing Cl-; also account for the change using the reaction quotient Qc
- Will the concentration of NO2 increase, decrease, or remain the same when the equilibrium NO2Cl(g) + NO(g) ⇌ NOCl(g) + NO2(g) is disturbed by the following changes? (a) Adding NOCl (b) Adding NO (c) Removing NO (d) Adding NO2Cl; also account for the change using the reaction quotient Qc
Problem 119
- For the water–gas shift reaction CO1g2 + H2O1g2 ∆ CO21g2 + H21g2, ΔH° = - 41.2 kJ does the amount of H2 in an equilibrium mixture increase or decrease when the temperature is increased? How does Kc change when the temperature is decreased? Justify your answers using Le Châtelier's principle.
Problem 122
- The value of ΔH° for the reaction 3 O2(g) ⇌ 2 O3(g) is +285 kJ. Does the equilibrium constant for this reaction increase or decrease when the temperature increases? Justify your answer using Le Châtelier’s principle.
Problem 123
- Consider the exothermic reaction CoCl 2-1aq2 + 6 H O1l2 ∆ Co1H O2 2 + 1aq2 + 4 Cl-1aq2 which interconverts the blue CoCl 2- ion and the pink Co 2 +CoCl 2- increase or decrease when the following changes occur?(c) The solution is diluted with water.
Problem 124
- Consider the endothermic reaction Fe³⁺(aq) + Cl⁻(aq) ⇌ FeCl₂⁺(aq). Use Le Châtelier’s principle to predict how the equilibrium concentration of the complex ion FeCl₂⁺ will change when: (a) Fe(NO₃)₃ is added. (b) Cl⁻ is precipitated as AgCl by addition of AgNO₃. (d) A catalyst is added.
Problem 125
- Methanol (CH3OH) is manufactured by the reaction of carbon monoxide with hydrogen in the presence of a Cu/ZnO/Al2O3 catalyst: CO(g) + 2H2(g) ⇌ CH3OH(g) ΔH° = -91 kJ. Does the amount of methanol increase, decrease, or remain the same when an equilibrium mixture of reactants and products is subjected to the following changes? (a) The temperature is increased. (b) CO is added. (c) Helium is added. (d) The catalyst is removed.
Problem 126
- In the gas phase at 400 °C, isopropyl alcohol (rubbing alcohol) decomposes to acetone, an important industrial solvent: \[ \text{Isopropyl alcohol: }(\text{CH}_3)_2\text{CHOH(g)} \rightleftharpoons (\text{CH}_3)_2\text{CO(g) + H}_2\text{(g)} \\ \Delta H^\circ = + 57.3 \text{ kJ} \] Does the amount of acetone increase, decrease, or remain the same when an equilibrium mixture of reactants and products is subjected to the following changes? (c) Argon is added. (d) H₂ is added. (e) A catalyst is added.
Problem 127
- The following reaction is important in gold mining: 4 Au1s2 + 8 CN-1aq2 + O21g2 + 2 H2O1l2 ∆ 4 Au1CN22-1aq2 + 4 OH-1aq2For a reaction mixture at equilibrium, in which direction would the reaction go to reestablish equilibrium after each of the following changes? (a) Adding gold
Problem 128
- For the following reaction catalyzed by iridium, which is endothermic at 700 K: CaO(s) + CH₄(g) + 2 H₂O(g) ⇌ CaCO₃(s) + 4 H₂(g), how would the following changes affect the total quantity of CaCO₃ in the reaction mixture once equilibrium is reestablished at 700 K? (a) Increasing the temperature (b) Adding calcium oxide (c) Removing methane (CH₄) (d) Adding iridium.
Problem 129
- The equilibrium constant Kp for the reaction PCl51g2 ∆ PCl31g2 + Cl21g2 is 3.81 * 102 at 600 K and 2.69 * 103 at 700 K. (b) How are the equilibrium amounts of reactants and products affected by (iii) addition of a catalyst?
Problem 130
- Baking soda (sodium bicarbonate) decomposes when it is heated: 2 NaHCO31s2 ∆ Na2CO31s2 + CO21g2 + H2O1g2 ΔH° = + 136 kJ Consider an equilibrium mixture of reactants and products in a closed container. How does the number of moles of CO2 change when the mixture is disturbed by the following: (b) Adding water vapor
Problem 131