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American Chemical Society General Chemistry Kinetics and Equilibrium

Rate laws, half-life, equilibrium constants, and Le Chatelier's principle.

These questions are original. This is not an official American Chemical Society exam, and FreeExam is not affiliated with the American Chemical Society.

  1. 1.In a sealed flask, [N2O5] falls from 0.80 M to 0.20 M in 40 s. What is the average rate of disappearance of N2O5?

  2. 2.Hydrogen iodide starts at 0 M and reaches 0.040 M after 10 s. What is the average rate of appearance of HI?

  3. 3.A bromine sample is 0.50 M at 20 s and 0.35 M at 50 s. What is the average rate of disappearance of Br2 on that interval?

  4. 4.Oxygen produced by a decomposition rises from 0.12 M to 0.36 M in 80 s. What is the average rate of appearance of O2?

  5. 5.In a smog chamber, [NO2] falls from 1.20 M to 0.40 M during 200 s. What is the average rate of disappearance of NO2?

  6. 6.SO3 is 0.15 M at t = 10 s and 0.45 M at t = 40 s. What average rate of formation fits those two readings?

  7. 7.Chlorine in a closed bottle drops from 0.90 M to 0.30 M in 2.0 minutes. What is the average rate of disappearance of Cl2, in M/min?

  8. 8.A timer reads 5.0 s when [C2H5OH] = 0.050 M and 20.0 s when [C2H5OH] = 0.200 M. What is the average rate of appearance of ethanol?

  9. 9.During a hydrogenation, [H2] falls from 0.90 M to 0.30 M in 100 s. What is the average rate of disappearance of H2?

  10. 10.For rate = k[A]^m[B]^n, run 1 has [A] = 0.10 M, [B] = 0.10 M, and rate 0.020 M/s. Run 2 has [A] = 0.20 M, [B] = 0.10 M, and rate 0.040 M/s. What is the order in A?

  11. 11.[B] is held at 0.20 M. Raising [A] from 0.10 M to 0.30 M changes the initial rate from 0.015 M/s to 0.135 M/s. What is the order in A?

  12. 12.[A] stays at 0.30 M while [B] goes from 0.25 M to 0.50 M. The initial rate goes from 0.0060 M/s to 0.024 M/s. What is the order in B?

  13. 13.[B] is fixed at 0.10 M. Tripling [A] from 0.15 M to 0.45 M leaves the initial rate at 0.018 M/s. What is the order in A?

  14. 14.[A] is constant at 0.20 M. Increasing [B] from 0.10 M to 0.40 M raises the rate from 0.012 M/s to 0.048 M/s. What is the order in B?

  15. 15.With [B] fixed at 0.15 M, [A] is raised from 0.20 M to 0.60 M and the rate rises from 0.010 M/s to 0.090 M/s. What is the order in A?

  16. 16.[B] stays at 0.30 M. Changing [A] from 0.050 M to 0.20 M changes the rate from 0.0060 M/s to 0.024 M/s. What is the order in A?

  17. 17.[A] is held at 0.40 M. Raising [B] from 0.10 M to 0.40 M does not change the rate from 0.025 M/s. What is the order in B?

  18. 18.[B] is constant at 0.50 M. Doubling [A] from 0.10 M to 0.20 M changes the rate from 0.0040 M/s to 0.032 M/s. What is the order in A?

  19. 19.The rate law is rate = k[N2O5], and the rate is measured in M/s. What are the units of k?

  20. 20.A second-order law is rate = k[NO]^2, with the rate in M/s. What are the units of k?

  21. 21.SO2Cl2 decomposes by the first-order law rate = k[SO2Cl2], and the rate is recorded in M/min. What are the units of k?

  22. 22.Chlorine disappears by rate = k[Cl2]^2, and the rate is in M/min. What are the units of this second-order k?

  23. 23.The law rate = k[NO][O2] is second order overall. The rate is in M/s. What are the units of k?

  24. 24.A measured rate constant has units of s^-1. Which rate law matches those units?

  25. 25.Nitrogen dioxide follows rate = k[NO2]^2, and the rate is measured in M/h. What are the units of k?

  26. 26.A first-order constant comes from rate = k[A], with the rate in mol/(L s). Which units does k have?

  27. 27.A student reports k = 0.40 M^-1 s^-1. Which rate law fits that unit?

  28. 28.A first-order decomposition of N2O5 has a half-life of 12 min, and the next half-life is also 12 min. What fraction remains after 3 half-lives?

  29. 29.Hydrogen peroxide decays by a first-order process with a constant half-life of 5.0 h. How much of a 64.0 g sample remains after 20.0 h?

  30. 30.SO2Cl2 decomposes with a constant first-order half-life of 30 s. A solution starts at 2.40 M. What concentration remains after 90 s?

  31. 31.A first-order rearrangement has a half-life that does not depend on concentration. What fraction of the starting amount remains after 2 half-lives?

  32. 32.Cyclopropane rearranges with a constant first-order half-life of 8.0 min. How much of an 80.0 mg sample remains after 24.0 min?

  33. 33.A first-order gas decomposition has a half-life of 10 min that stays 10 min as the amount falls. How much of 1.60 mol remains after 40 min?

  34. 34.A first-order decomposition has a constant half-life. What fraction of the original sample remains after 5 half-lives?

  35. 35.A first-order decay has a constant half-life of 15 s. The starting concentration is 0.48 M. What remains after 60 s?

  36. 36.A first-order process has a constant half-life of 4.0 min. How much of a 96 mmol sample remains after 12 min?

  37. 37.Manganese dioxide catalyzes the decomposition of hydrogen peroxide at constant temperature. What happens to the activation energy and to K?

  38. 38.A sample of N2O5 is warmed and no catalyst is added. Which statement agrees with the Arrhenius idea?

  39. 39.An ester hydrolysis can be heated, or run with an acid catalyst at the original temperature. Which comparison is correct?

  40. 40.An iron catalyst is added to N2(g) + 3H2(g) equilibrium with 2NH3(g) at constant temperature. What is true of the rates and of K?

  41. 41.A reversible reaction is at equilibrium at a fixed temperature. Which change increases both the forward and reverse rates and leaves K unchanged?

  42. 42.The activation energy of a reaction is fixed and the temperature is increased. According to Arrhenius, what happens to the rate constant k?

  43. 43.A student says a catalyst raises K because it lowers only the forward activation energy. Which correction is right?

  44. 44.Two flasks hold the same uncatalyzed mixture. Flask 2 is hotter than flask 1. Which comparison of the rate constants is right?

  45. 45.At one temperature, the same reaction is compared with and without a catalyst. Which statement is right?

  46. 46.Hydrogen and iodine form hydrogen iodide by H2(g) + I2(g) equilibrium with 2HI(g). Which expression is Kc?

  47. 47.Ammonia forms by N2(g) + 3H2(g) equilibrium with 2NH3(g). Which expression is Kp?

  48. 48.Sulfur trioxide forms by 2SO2(g) + O2(g) equilibrium with 2SO3(g). Which expression is Kc?

  49. 49.Phosphorus pentachloride decomposes by PCl5(g) equilibrium with PCl3(g) + Cl2(g). Which expression is Kp?

  50. 50.Nitric oxide is oxidized by 2NO(g) + O2(g) equilibrium with 2NO2(g). Which expression is Kc?

  51. 51.Methanol forms by CO(g) + 2H2(g) equilibrium with CH3OH(g). Which expression is Kp?

  52. 52.Dinitrogen tetroxide dissociates by N2O4(g) equilibrium with 2NO2(g). Which expression is Kc?

  53. 53.Water vapor forms from the elements by 2H2(g) + O2(g) equilibrium with 2H2O(g). Which expression is Kc?

  54. 54.Carbon monoxide burns by 2CO(g) + O2(g) equilibrium with 2CO2(g). Which expression is Kp?

  55. 55.At the moment of mixing, Q = 1.0 for a reaction whose K is 4.0. Which way does the reaction shift?

  56. 56.A reaction has K = 0.25. Just after mixing, Q = 2.0. Which way does the system shift?

  57. 57.A mixture is prepared so that Q = 16 and K = 16. What does the reaction do?

  58. 58.For a reaction, K = 0.10 and the reaction quotient just after mixing is Q = 0.010. Which way is the shift?

  59. 59.K = 50 for a gas reaction, and a freshly mixed sample has Q = 80. Which way does the equilibrium shift?

  60. 60.For H2(g) + I2(g) equilibrium with 2HI(g), Kc = 49. A mixture has [H2] = 0.20 M, [I2] = 0.20 M, and [HI] = 0.40 M. Which way does it shift?

  61. 61.For 2NO2(g) equilibrium with N2O4(g), Kc = 2.0. A mixture has [NO2] = 0.50 M and [N2O4] = 2.0 M. Which way does it shift?

  62. 62.For PCl5(g) equilibrium with PCl3(g) + Cl2(g), Kc = 0.40. Concentrations are [PCl5] = 0.50 M, [PCl3] = 0.20 M, and [Cl2] = 0.20 M. Which way does it shift?

  63. 63.For N2(g) + 3H2(g) equilibrium with 2NH3(g), Kc = 0.50. A mixture has [N2] = 1.0 M, [H2] = 1.0 M, and [NH3] = 1.0 M. Which way does it shift?

  64. 64.Nitrogen is added to N2(g) + 3H2(g) equilibrium with 2NH3(g) at constant volume and temperature. Which way does the equilibrium shift?

  65. 65.Sulfur trioxide is removed from 2SO2(g) + O2(g) equilibrium with 2SO3(g) at constant volume and temperature. Which way does the equilibrium shift?

  66. 66.The volume of 2SO2(g) + O2(g) equilibrium with 2SO3(g) is decreased at constant temperature. Which way does the equilibrium shift?

  67. 67.The container volume for PCl5(g) equilibrium with PCl3(g) + Cl2(g) is increased at constant temperature. Which way does the equilibrium shift?

  68. 68.For N2O4(g) equilibrium with 2NO2(g), the forward reaction is endothermic. The mixture is heated at constant volume. Which way does the equilibrium shift?

  69. 69.For 2SO2(g) + O2(g) equilibrium with 2SO3(g), the forward reaction is exothermic. The mixture is heated. Which way does the equilibrium shift?

  70. 70.Extra Cl2 is added to PCl5(g) equilibrium with PCl3(g) + Cl2(g) at constant volume and temperature. Which way does the equilibrium shift?

  71. 71.The volume of H2(g) + I2(g) equilibrium with 2HI(g) is halved at constant temperature. Which way does the equilibrium shift?

  72. 72.For CO(g) + 2H2(g) equilibrium with CH3OH(g), the forward reaction is exothermic. The mixture is cooled at constant volume. Which way does the equilibrium shift?

  73. 73.For SO2Cl2(g) equilibrium with SO2(g) + Cl2(g), Kc = 1.0 x 10^-5. The flask starts with 0.10 M SO2Cl2 and no products. Using the small-x approximation, what is [Cl2] at equilibrium?

  74. 74.N2O4(g) equilibrium with 2NO2(g) starts at 0.50 M N2O4 and no NO2. At equilibrium [NO2] = 0.20 M. What is Kc?

  75. 75.The isomerization A(g) equilibrium with B(g) has Kc = 2.0 x 10^-4. The mixture starts at 0.50 M A and no B. With the small-x approximation, what is [B] at equilibrium?

  76. 76.H2(g) + I2(g) equilibrium with 2HI(g) starts with [H2] = 0.30 M, [I2] = 0.30 M, and no HI. At equilibrium [HI] = 0.20 M. What is Kc?

  77. 77.For PCl5(g) equilibrium with PCl3(g) + Cl2(g), Kc = 4.0 x 10^-6. The vessel starts with 0.25 M PCl5 and no products. Using the small-x approximation, what is [PCl3] at equilibrium?

  78. 78.An isomerization A equilibrium with B starts at 0.60 M A and no B. At equilibrium [A] = 0.40 M. What is Kc?

  79. 79.PCl5(g) equilibrium with PCl3(g) + Cl2(g) starts at 1.00 M PCl5. At equilibrium [Cl2] = 0.20 M. What is Kc?

  80. 80.For M(g) equilibrium with N(g), Kc = 5.0 x 10^-3. The sample starts at 0.20 M M and no N. With the small-x approximation, what is [N] at equilibrium?

  81. 81.CO(g) + Cl2(g) equilibrium with COCl2(g) starts at [CO] = 0.80 M and [Cl2] = 0.50 M, with no COCl2. At equilibrium [COCl2] = 0.30 M. What is Kc?

  82. 82.For H2(g) + I2(g) equilibrium with 2HI(g), delta n = 0. The temperature is 700 K and Kc = 46. What is Kp?

  83. 83.For PCl5(g) equilibrium with PCl3(g) + Cl2(g), delta n = 1 and RT = 2.0 at the stated temperature. Kc = 5.0. What is Kp?

  84. 84.For 2SO2(g) + O2(g) equilibrium with 2SO3(g), delta n = -1 and RT = 4.0. Kc = 8.0. What is Kp?

  85. 85.For N2(g) + 3H2(g) equilibrium with 2NH3(g), Kc = 0.50. The temperature is not given. What can be said about Kp?

  86. 86.For H2(g) + Br2(g) equilibrium with 2HBr(g), which relation of Kp and Kc is true at every temperature?

  87. 87.For 2NH3(g) equilibrium with N2(g) + 3H2(g), delta n = 2 and RT = 3.0. Kc = 4.0. What is Kp?

  88. 88.For N2(g) + 3H2(g) equilibrium with 2NH3(g), delta n = -2 and RT = 2.0. Kc = 16. What is Kp?

  89. 89.A gas reaction has delta n = 1. The mixture is heated. What happens to the factor that converts Kc into Kp, apart from any change in K itself?

  90. 90.For 2NO2(g) equilibrium with N2O4(g), delta n = -1 and RT = 5.0 at the stated temperature. How is Kp related to Kc?

  91. 91.Kc = 4.0 for PCl5(g) equilibrium with PCl3(g) + Cl2(g). What is Kc for the reverse reaction, PCl3(g) + Cl2(g) equilibrium with PCl5(g)?

  92. 92.Kc = 3.0 for a reaction as written. Every coefficient in the equation is doubled. What is the new equilibrium constant?

  93. 93.Kc = 25 for 2SO2(g) + O2(g) equilibrium with 2SO3(g). What is Kc for 2SO3(g) equilibrium with 2SO2(g) + O2(g)?

  94. 94.K = 0.20 for N2O4(g) equilibrium with 2NO2(g). What is K for the doubled equation 2N2O4(g) equilibrium with 4NO2(g)?

  95. 95.Kc = 2.0 for H2(g) + I2(g) equilibrium with 2HI(g). What is Kc for 2HI(g) equilibrium with H2(g) + I2(g)?

  96. 96.An equilibrium constant is 5.0. The chemical equation is multiplied through by 2. What is the equilibrium constant of the doubled equation?

  97. 97.The forward equilibrium constant is 16. What is the equilibrium constant of the reverse reaction?

  98. 98.K = 4.0 for A equilibrium with B. The equation is reversed, and that reversed equation is then doubled. What is the new equilibrium constant?

  99. 99.Kc = 0.50 for CO(g) + Cl2(g) equilibrium with COCl2(g). What is Kc when that equation is written in reverse?

  100. 100.Calcium carbonate decomposes by CaCO3(s) equilibrium with CaO(s) + CO2(g). Which expression is Kc?

  101. 101.Steam passes over hot carbon: C(s) + H2O(g) equilibrium with CO(g) + H2(g). Which expression is Kc?

  102. 102.Liquid water is in equilibrium with its vapor, H2O(l) equilibrium with H2O(g). Which expression is Kc?

  103. 103.Silver chloride dissolves slightly by AgCl(s) equilibrium with Ag+(aq) + Cl-(aq). Which expression is Kc?

  104. 104.Iron(II) oxide is reduced by FeO(s) + CO(g) equilibrium with Fe(s) + CO2(g). Which expression is Kc?

  105. 105.Solid carbon reacts with carbon dioxide by C(s) + CO2(g) equilibrium with 2CO(g). Which expression is Kc?

  106. 106.A saturated solution already contains AgCl(s). More AgCl(s) is added at constant temperature. What happens to [Ag+][Cl-]?

  107. 107.Calcium hydroxide dissolves by Ca(OH)2(s) equilibrium with Ca2+(aq) + 2OH-(aq). Which expression is Kc?

  108. 108.Nickel tetracarbonyl forms by Ni(s) + 4CO(g) equilibrium with Ni(CO)4(g). Which expression is Kc?