Chapter 14 – Chemical Equilibrium
Chapter 14
Chemical Equilibrium
Chapter 14 – Chemical Equilibrium
2. Which is the correct equilibrium constant expression for the following reaction?
Fe2O3 (s) + 3H2 (g) 2Fe (s) + 3H2O (g)
3. The equilibrium constant expression for the reaction: N2 (g) + O2 (g) 2NO (g) is
4. The equilibrium constant expression for the reaction 2BrF5 (g) Br2 (g) + 5F2 (g) is
Chapter 14 – Chemical Equilibrium
5. A reaction with an equilibrium constant Kc = 1.5 x 10–25 would consist of which of the
following at equilibrium:
6. A reaction with an equilibrium constant Kc = 1.5 x 1021 would consist of which of the
following at equilibrium:
Chapter 14 – Chemical Equilibrium
7. The solubility of silver chloride can be increased by dissolving it in a solution containing
ammonia.
AgCl (s) Ag+ (aq) + Cl– (aq) K1 = 1.6 x 10–10
Ag+ (aq) + 2NH3 (aq) Ag(NH3)2+ (aq) K2 = 1.5 x 107
What is the value of the equilibrium constant for the overall reaction?
AgCl (s) + 2NH3 (aq) Ag(NH3)2+ (aq) + Cl– (aq) Knet = ?
8. The solubility of silver bromide can be increased by dissolving it in a solution containing
the thiosulfate anion.
AgBr(s) Ag+ (aq) + Br– (aq) K1 = 7.7 x 10–13
Ag+(aq) + 2S2O32- (aq) Ag(S2O3)23- (aq) K2 = 4.7 x 1013
What is the value of the equilibrium constant for the overall reaction?
AgBr(s) + 2S2O32-(aq) Ag(S2O3)23-(aq) + Br–(aq)
Chapter 14 – Chemical Equilibrium
9.
Consider the two gaseous equilibria:
The values of the equilibrium constants K1 and K2 are related by
10. Carbon tetrachloride reacts at high temperatures with oxygen to produce two toxic gases,
phosgene and chlorine.
CCl4(g) + 1/2O2(g) COCl2(g) + Cl2(g), Kc = 4.4 109 at 1,000 K
Calculate Kc for the reaction 2CCl4(g) + O2(g) 2COCl2(g) + 2Cl2(g).
Chapter 14 – Chemical Equilibrium
11. The equilibrium constant for the reaction Ni(s) + 4CO(g) Ni(CO)4(g) is 5.0 104 at
12. Given the following information:
2A(g) + B(g) A2B(g) Kp1
2A(g) + C2(g) 2AC(g) Kp2
3/2A2(g) + B(g) + C(g) AC(g) + A2B(g) Kp3
Which relationship represents the equilibrium constant for the reaction:
3A2(g) + 3B(g) + 2C(g) 3A2B(g) + C2(g) Knet = ?
Chapter 14 – Chemical Equilibrium
13. Given the following information:
2A(g) + B(g) A2B(g) Kp1
2A(g) + C2(g) 2AC(g) Kp2
3/2 A2 + B(g) + C(g) AC(g) + A2B(g) Kp3
Which relationship represents the equilibrium constant for the reaction:
4A(g) + C2(g) + A2B(g) 3A2(g) + B(g) + 2C(g)
14. When the following reaction is at equilibrium, which of these relationships is always true?
2NOCl(g) 2NO(g) + Cl2(g)
Chapter 14 – Chemical Equilibrium
15. When the following reaction is at equilibrium, which of these relationships is always true?
2 O3(g) 3 O2(g)
16. Calculate Kp for the reaction 2NOCl(g) 2NO(g) + Cl2(g) at 400C if Kc at 400C for
this reaction is 2.1 10–2.
Chapter 14 – Chemical Equilibrium
17. On analysis, an equilibrium mixture for the reaction 2H2S(g) 2H2(g) + S2(g) was found
to contain 1.0 mol H2S, 4.0 mol H2, and 0.80 mol S2 in a 4.0 L vessel. Calculate the
equilibrium constant, Kc, for this reaction.
18. 2.50 mol NOCl was placed in a 2.50 L reaction vessel at 400ºC. After equilibrium was
established, it was found that 28% of the NOCl had dissociated according to the equation
2NOCl(g) 2NO(g) + Cl2(g).
Calculate the equilibrium constant, Kc, for the reaction.
Chapter 14 – Chemical Equilibrium
19. 1.25 moles of NOCl were placed in a 2.50 L reaction chamber at 427ºC. After equilibrium
was reached, 1.10 moles of NOCl remained. Calculate the equilibrium constant, Kc, for the
reaction 2NOCl(g) 2NO(g) + Cl2(g).
20. The reaction A(g) + 2B(g) C(g) was allowed to come to equilibrium. The initial
amounts of reactants placed into a 5.00 L vessel were 1.0 mol A and 1.8 mol B. After the
Chapter 14 – Chemical Equilibrium
21. The brown gas NO2 and the colorless gas N2O4 exist in equilibrium, 2NO2 N2O4. In an
experiment, 0.625 mole of N2O4 was introduced into a 5.00 L vessel and was allowed to
decompose until equilibrium was reached. The concentration of N2O4 at equilibrium was
0.0750 M. Calculate Kc for the reaction.
22. Calculate Kc for the reaction 2HI(g) H2(g) + I2(g) given that the concentrations of each
species at equilibrium are as follows: [HI] = 0.85 mol/L, [I2] = 0.60 mol/L, [H2] = 0.27
mol/L.
Chapter 14 – Chemical Equilibrium
23. Phosgene, COCl2, a poisonous gas, decomposes according to the equation COCl2(g)
CO(g) + Cl2(g). Calculate Kp for this reaction if Kc = 0.083 at 900ºC.
24. Kp for the reaction CO2(g) + C(s) 2CO(g) is 1.47 at 727C. Calculate Kc at this
temperature.
Chapter 14 – Chemical Equilibrium
25. Kp for the reaction 4CuO(s) 2Cu2O(s) + O2(g) is 0.49 at 1024 C. Calculate Kc at this
temperature
26. Kp for the reaction of SO2(g) with O2 to produce SO3(g) is 3 1024 . Calculate Kc for this
equilibrium at 25ºC. (The relevant reaction is 2SO2(g) + O2(g) 2SO3(g).)
Chapter 14 – Chemical Equilibrium
27. If one starts with pure NO2(g) at a pressure of 0.500 atm, the total pressure inside the
reaction vessel when 2NO2(g) 2NO(g) + O2(g) reaches equilibrium is 0.674 atm. Calculate
the equilibrium partial pressure of NO2.
28. Equilibrium is established for the reaction 2X(s) + Y(g) 2Z(g) at 500K, Kc = 100.
Chapter 14 – Chemical Equilibrium
29. At 250ºC, the equilibrium constant Kp for the reaction PCl5(g) PCl3(g) + Cl2(g) is 1.80.
Sufficient PCl5 is put into a reaction vessel to give an initial pressure of 2.74 atm at 250ºC.
30. At 35ºC, the equilibrium constant for the reaction 2NOCl(g) 2NO(g) + Cl2(g) is Kc =
1.6 10–5. An equilibrium mixture was found to have the following concentrations of Cl2 and
NOCl: [Cl2] = 1.2 10–2 M; [NOCl] = 2.8 10–1 M. Calculate the concentration of NO(g) at
equilibrium.
Chapter 14 – Chemical Equilibrium
31. For the reaction SO2(g) + NO2(g) SO3(g) + NO(g), the equilibrium constant is 18.0 at
1,200ºC. If 1.0 mole of SO2 and 2.0 moles of NO2 are placed in a 20. L container, what
concentration of SO3 will be present at equilibrium?
32. Consider the reaction N2(g) + O2(g) 2NO(g), for which Kc = 0.10 at 2,000ºC. Starting
with initial concentrations of 0.040 M of N2 and 0.040 M of O2, determine the equilibrium
concentration of NO.
Chapter 14 – Chemical Equilibrium
33. Hydrogen iodide decomposes according to the equation 2HI(g) H2(g) + I2(g), for
which Kc = 0.0156 at 400ºC. 0.550 mol HI was injected into a 2.00 L reaction vessel at 400ºC.
Calculate the concentration of HI at equilibrium.
34. Hydrogen iodide decomposes according to the equation 2HI(g) H2(g) + I2(g), for
which Kc = 0.0156 at 400ºC. 0.550 mol HI was injected into a 2.00 L reaction vessel at 400ºC.
Calculate the concentration of H2 at equilibrium.
Chapter 14 – Chemical Equilibrium
35. At 400ºC, Kc = 64 for the equilibrium H2(g) + I2(g) 2HI(g). If 3.00 mol H2 and 3.00
mol I2 are introduced into an empty 4.0 L vessel, find the equilibrium concentration of HI at
400ºC.
36. Sodium carbonate, Na2CO3(s), can be prepared by heating sodium bicarbonate,
NaHCO3(s) as shown below.
2NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g) Kp = 0.23 at 100ºC
If a sample of NaHCO3 is placed in an evacuated flask and allowed to achieve equilibrium at
100ºC, what will the total gas pressure be?
Chapter 14 – Chemical Equilibrium
37. At 340 K, Kp = 69 for the reaction H2(g) + I2(g) 2HI(g). 50.0 g of HI is injected into an
evacuated 5.00-L rigid cylinder at 340 K. What is the total pressure inside the cylinder when
the system comes to equilibrium?
38. 15.00 g of solid ammonium hydrogen sulfide is introduced into a 500.-mL flask at 25C,
the flask is sealed, and the system is allowed to reach equilibrium. What is the partial pressure
of ammonia in this flask if Kp = 0.108 at 25C for NH4HS(s) NH3(g) + H2S (g)?
Chapter 14 – Chemical Equilibrium
39. For the nitrogen fixation reaction 3H2(g) + N2(g) 2NH3(g), Kc = 6.0 10–2 at 500C. If
0.250 M H2 and 0.050 M NH3 are present at equilibrium, what is the equilibrium
concentration of N2?
40.
Consider the following reactions and their associated equilibrium constants:
For the reaction A + 2B D + E, having equilibrium constant Kc,