Chapter 13 Practice Problems

Chemical Kinetics Chapter 13 Problem Set I 1. Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction: 2NO2 → 2NO + O2 In a particular experiment at 300 °C, [NO2] drops from 0.0100 to 0.00650 M in 100 s. The rate of disappearance of NO 2 for this period is __________ M/s. A) 0.35 B) 3.5 × 10-3 C) 3.5 × 10-5 D) 7.0 × 10-3 E) 1.8 × 10-3 2. At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen: 2N2O5(g) → 4NO2 (g) + O2 (g) When the rate of formation of O2 is 2.2 × 10-4 M/s, the rate of decomposition of N2O5 is __________ M/s. A) 1.1 × 10-4 B) 2.2 × 10-4 C) 2.8 × 10-4 D) 4.4 × 10-4 E) 5.5 × 10-4 3. Which one of the following is not a valid expression for the rate of the reaction below? 4NH3 + 7O2 → 4NO2 + 6H2O 1 Δ  O2  7Δt 1 Δ  NO 2  A)  B) C) 4Δt 1 Δ  H 2O 6Δt 1 Δ  NH3  D)  4Δt E) All of the above are valid expressions of the reaction rate. 1 4. The rate law of a reaction is rate = k[D][X]. The units of the rate constant are __________. A) mol L-1s-1 B) L mol-1s-1 C) mol2 L-2s-1 D) mol L-1s-2 E) L2 mol -2s-1 The data in the table below were obtained for the reaction: A + B → P 5. The rate law for this reaction is rate = __________. A) k[A][B] B) k[P] C) k[A]2[B] D) k[A]2[B]2 E) k[A]2 6. The magnitude of the rate constant is __________. A) 38.0 B) 0.278 C) 13.2 D) 42.0 E) 2.21 The data in the table below were obtained for the reaction: 2 ClO2 (aq) + 2 OH- (aq) → ClO3- (aq) + ClO2- (aq) + H2O 7. What is the order of the reaction with respect to ClO2? A) 1 B) 0 C) 2 D) 3 E) 4 2 8. What is the order of the reaction with respect to OH -? A) 0 B) 1 C) 2 D) 3 E) 4 9. What is the overall order of the reaction? A) 4 B) 0 C) 1 D) 2 E) 3 10. What is the magnitude of the rate constant for the reaction? A) 1.15 × 104 B) 4.6 C) 230 D) 115 E) 713 11. The rate law for a reaction is rate = k [A][B]2 Which one of the following statements is false? A) The reaction is first order in A. B) The reaction is second order in B. C) The reaction is second order overall. D) k is the reaction rate constant E) If [B] is doubled, the reaction rate will increase by a factor of 4. 12. The decomposition of N2O5 in solution in carbon tetrachloride proceeds via the reaction 2N2O5 (soln) → 4NO2 (soln) + O2 (soln) The reaction is first order and has a rate constant of 4.82 × 10 -3 s-1 at 64°C. The rate law for the reaction is rate = __________. A) k[N2O5]2 4  NO2   O2  B) k 2  N 2 O5  C) k[N2O5] 2  N 2O 5  D) k 4  NO2   O2  E) 2k[N2O5] As the temperature of a reaction is increased, the rate of the reaction increases because the __________. A) reactant molecules collide less frequently B) reactant molecules collide more frequently and with greater energy per collision C) activation energy is lowered D) reactant molecules collide less frequently and with greater energy per collision E) reactant molecules collide more frequently with less energy per collision 3 13. The rate of a reaction depends on __________. A) collision frequency B) collision energy C) collision orientation D) all of the above E) none of the above 14. Which energy difference in the energy profile below corresponds to the activation energy for the forward reaction? A) x B) y C) x + y D) x - y E) y - x 15. In the energy profile of a reaction, the species that exists at the maximum on the curve is called the __________. A) product B) activated complex C) activation energy D) enthalpy of reaction E) atomic state 16. In the Arrhenius equation, k = Ae-Ea/RT__________ is the frequency factor. A) k B) A C) e D) Ea E) R 17. In general, as temperature goes up, reaction rate __________. A) goes up if the reaction is exothermic B) goes up if the reaction is endothermic C) goes up regardless of whether the reaction is exothermic or endothermic D) stays the same regardless of whether the reaction is exothermic or endothermic E) stays the same if the reaction is first order 18. In general, as temperature goes down, reaction rate __________. A) goes down if the reaction is exothermic B) goes down if the reaction is endothermic C) stays the same regardless of whether the reaction is exothermic or endothermic D) goes down regardless of whether the reaction is exothermic or endothermic E) none of the above 4 19. At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN): CH3NC (g) → CH3CN (g) The dependence of the rate constant on temperature is studied and the graph below is prepared from the results. The energy of activation of this reaction is __________ kJ/mol. A) 160 B) 1.6 × 105 C) 4.4 × 10-7 D) 4.4 × 10-4 E) 1.9 × 104 20. The mechanism for formation of the product X is: A + B → C + D B + D→ X (slow) (fast) The intermediate reactant in the reaction is __________. A) A B) B C) C D) D E) X 21. For the elementary reaction NO3 + CO → NO2 + CO2 the molecularity of the reaction is __________, and the rate law is rate = __________. A) 2, k[NO3][CO] B) 4, k[NO3][CO][NO2][CO2] C) 2, k[NO2][CO2] D) 2, k[NO3][CO]/[NO2][CO2] E) 4, k[NO2][CO2]/[NO3][CO] 5 22. Which of the following is true? A) If we know that a reaction is an elementary reaction, then we know its rate law. B) The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism. C) Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process. D) In a reaction mechanism, an intermediate is identical to an activated complex. E) All of the above statements are true. 23. Of the following, __________ will lower the activation energy for a reaction. A) increasing the concentrations of reactants B) raising the temperature of the reaction C) adding a catalyst for the reaction D) removing products as the reaction proceeds E) increasing the pressure 24. The rate law of the overall reaction A + B → C is rate = k[A]2. Which of the following will not increase the rate of the reaction? A) increasing the concentration of reactant A B) increasing the concentration of reactant B C) increasing the temperature of the reaction D) adding a catalyst for the reaction E) All of these will increase the rate. 25. A catalyst can increase the rate of a reaction __________. A) by changing the value of the frequency factor (A) B) by increasing the overall activation energy (Ea) of the reaction C) by lowering the activation energy of the reverse reaction D) by providing an alternative pathway with a lower activation energy E) All of these are ways that a catalyst might act to increase the rate of reaction. 26. The primary source of the specificity of enzymes is __________. A) their polarity, which matches that of their specific substrate B) their delocalized electron cloud C) their bonded transition metal, which is specific to the target substrate D) their locations within the cell E) their shape, which relates to the lock-and-key model 27. __________ are used in automotive catalytic converters. A) Heterogeneous catalysts B) Homogeneous catalysts C) Enzymes D) Noble gases E) Nonmetal oxides 28. Consider the following reaction: 3A → 2B . The average rate of appearance of B is given by Δ[B]/Δt. Comparing the rate of appearance of B and the rate of disappearance of A, we get Δ[B]/Δt = __________ × (-Δ[A]/Δt). A) -2/3 B) +2/3 C) -3/2 D) +1 E) +3/2 6 29. Which substance in the reaction below either appears or disappears the fastest? 4NH3 + 7O2 → 4NO2 + 6H2O A) NH3 B) O2 C) NO2 D) H2O E) The rates of appearance/disappearance are the same for all of these. 30. Consider the following reaction: A → 2C The average rate of appearance of C is given by Δ[C]/Δt. Comparing the rate of appearance of C and the rate of disappearance of A, we get Δ[C]/Δt = __________ × (-Δ[A]/Δt). A) +2 B) -1 C) +1 D) +1/2 E) -1/2 31. At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen: 2N2O5(g) → 4NO2 (g) + O2 (g) When the rate of formation of NO2 is 5.5 × 10-4 M/s, the rate of decomposition of N2O5 is ________ M/s. A) 2.2 × 10-3 B) 1.4 × 10-4 C) 10.1 × 10-4 D) 2.8 × 10-4 E) 5.5 × 10-4 32. A reaction was found to be second order in carbon monoxide concentration. The rate of the reaction __________ if the [CO] is doubled, with everything else kept the same. A) doubles B) remains unchanged C) triples D) increases by a factor of 4 E) is reduced by a factor of 2 33. If the rate law for the reaction 2A + 3B → products is first order in A and second order in B, then the rate law is rate = __________. A) k[A][B] B) k[A]2[B]3 C) k[A][B]2 D) k[A]2[B] E) k[A]2[B]2 7 34. If the rate law for the reaction 2A + 3B → products is second order in A and first order in B, then the rate law is rate = __________. A) k[A][B] B) k[A]2[B]3 C) k[A][B]2 D) k[A]2[B] E) k[A]2[B]2 35. The overall order of a reaction is 1. The units of the rate constant for the reaction are __________. A) M/s B) M-1s-1 C) 1/s D) 1/M E) s/M2 36. The overall order of a reaction is 2. The units of the rate constant for the reaction are __________. A) M/s B) M-1s-1 C) 1/s D) 1/M E) s/M2 37. The kinetics of the reaction below were studied and it was determined that the reaction rate increased by a factor of 9 when the concentration of B was tripled. The reaction is __________ order in B. A + B → P A) zero B) first C) second D) third E) one-half 38. The kinetics of the reaction below were studied and it was determined that the reaction rate did not change when the concentration of B was tripled. The reaction is __________ order in B. A + B → P A) zero B) first C) second D) third E) one-half 39. A reaction was found to be third order in A. Increasing the concentration of A by a factor of 3 will cause the reaction rate to __________. A) remain constant B) increase by a factor of 27 C) increase by a factor of 9 8 D) triple E) decrease by a factor of the cube root of 3 40. A reaction was found to be zero order in A. Increasing the concentration of A by a factor of 3 will cause the reaction rate to __________. A) remain constant B) increase by a factor of 27 C) increase by a factor of 9 D) triple E) decrease by a factor of the cube root of 3 The data in the table below were obtained for the reaction: A + B → P 41. The order of the reaction in A is __________. A) 1 B) 2 C) 3 D) 4 E) 0 42. The order of the reaction in B is __________. A) 1 B) 2 C) 3 D) 4 E) 0 43. The overall order of the reaction is __________. A) 1 B) 2 C) 3 D) 4 E) 0 44. The decomposition of HBr proceeds by the reaction: 2HBr (g) → H2 (g) + Br2 (g) When the rate of disappearance of HBr is 0.301 Ms -1 at 150°C, the rate of appearance of Br2 is __________ Ms-1. A) 1.66 B) 0.151 C) 0.0906 D) 0.602 E) 0.549 45. The combustion of ethylene proceeds by the reaction: C 2H4(g) + 3O2 (g) → 2CO2 (g) + 2H2O (g) When the rate of disappearance of O2 is 0.28 Ms-1, the rate of appearance of CO2 is __________ Ms-1. A) 0.19 B) 0.093 C) 0.84 9 D) 0.42 E) 0.56 10