CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

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1 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40 1. Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO 2 (aq) + 2OH (aq) ClO 2 (aq) + ClO 3 (aq) + H 2 O(l) Under a certain set of conditions, the initial rate of disappearance of chlorine dioxide was determined to be 2.30 x 10 1 M/s. What is the initial rate of appearance of chlorite ion under those same conditions? A x 10 2 M/s B x 10 1 M/s C x 10 1 M/s D x 10 1 M/s E x 10 1 M/s 2. For the reaction BrO 3 + 5Br + 6H + 3Br 2 + 3H 2 O at a particular time, [BrO 3 ]/ t = M/s. What is [Br ]/ t at the same instant? A. 13 M/s B M/s C M/s D M/s E. 330 M/s 3. For the following reaction, P(C 6 H 14 )/ t was found to be atm/s. C 6 H 14 (g) C 6 H 6 (g) + 4H 2 (g) Determine P(H 2 )/ t for this reaction at the same time. A atm/s B atm/s C atm/s D atm/s E atm/s 1 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

2 4. For the reaction C 6 H 14 (g) C 6 H 6 (g) + 4H 2 (g), P(H 2 )/ t was found to be atm/s, where P(H 2 ) is the change in pressure of hydrogen. Determine P(C 6 H 14 )/ t for this reaction at the same time. A atm/s B atm/s C atm/s D atm/s E atm/s 5. For the hypothetical reaction A + 3B 2C, the rate of appearance of C given by ( [C]/ t) may also be expressed as A. [C]/ t = [A]/ t B. [C]/ t = (3/2) [B]/ t C. [C]/ t = (2/3) [B]/ t D. [C]/ t = (1/2) [A]/ t 6. The reaction A + 2B products has the rate law, rate = k[a][b] 3. If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase? A. 2 B. 4 C. 6 D. 8 E. 9 2 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

3 7. Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO 2 (aq) + 2OH (aq) ClO 2 (aq) + ClO 3 (aq) + H 2 O(l) A kinetic study of this reaction under a certain set of conditions yielded the data below. Which one of the following is the rate law for this reaction? A. rate = k[clo 2 ][OH - ] B. rate = k[clo 2 ] 2 [OH - ] C. rate = k[clo 2 ][OH - ] 2 D. rate = k[clo 2 ] 2 [OH - ] 2 E. rate = k[clo 2 ] 4 [OH - ] 8. Nitric oxide gas (NO) reacts with chlorine gas according to the chemical equation given below. NO + ½Cl 2 NOCl The following initial rates of reaction have been measured for the given reagent concentrations. Which of the following is the rate law (rate equation) for this reaction? A. rate = k[no] B. rate = k[no][cl 2 ] 1/2 C. rate = k[no][cl 2 ] D. rate = k[no] 2 [Cl 2 ] E. rate = k[no] 2 [Cl 2 ] 2 3 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

4 9. A certain first-order reaction A B is 25% complete in 42 min at 25 C. What is the half-life of the reaction? A. 21 min B. 42 min C. 84 min D. 20 min E. 101 min 10. A certain reaction, reaction A products, is first order with respect to A. Starting with [A] = 0.250M, it takes 45 min to reduce the concentration of A to 0.110M. What is its rate constant for this reaction? A. 7.9 x 10-3 min -1 B. 1.1 x 10-1 min -1 C. 3.0 x 10-4 min -1 D. 1.8 x 10-2 min -1 E. 3.1 x 10-3 min Ammonium ion (NH 4 + ) reacts with nitrite ion (NO 2 ) to yield nitrogen gas and liquid water. The following initial rates of reaction have been measured for the given reactant concentrations. Which of the following is the rate law (rate equation) for this reaction? A. rate = k [NH 4 + ] [NO 2 ] 4 B. rate = k [NH 4 + ] [NO 2 ] C. rate = k [NH 4 + ] [NO 2 ] 2 D. rate = k [NH 4 + ] 2 [NO 2 ] E. rate = k [NH 4 + ] 1/2 [NO 2 ] 1/4 4 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

5 12. The isomerization of cyclopropane to form propene is a first-order reaction. At 760 K, 85% of a sample of cyclopropane changes to propene in 79.0 min. Determine the rate constant for this reaction at 760 K. A min 1 B min 1 C min 1 D min 1 E min At 700 K, the rate constant for the following reaction is min 1. How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene? A. 1,120 min B. 360 min C min D min E. 280 min 14. A certain reaction A products is second order with respect to A with a rate constant, k, M -1 min -1. Starting with [A] o = 1.01M, how many seconds will it take for A to reach a concentration of 0.750M? A s B s C. 893 s D. 169 s E. 128 s 5 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

6 15. At 25 C, the second-order reaction NOCl(g) NO(g) + 1 / 2 Cl 2 (g)is 50% complete after 5.82 hours when the initial concentration of NOCl is 4.46 mol/l. How long will it take for the reaction to be 75% complete? A hr B hr C hr D hr E hr 16. The thermal decomposition of acetaldehyde, CH 3 CHO CH 4 + CO, is a second-order reaction. The following data were obtained at 518 C. Based on the data given, what is the half-life for the disappearance of acetaldehyde? A s B. 410 s C s D. 520 s E. 305 s 17. In general, to calculate the rate constant for a first order decomposition reaction, A products, given the time needed to decrease the initial concentration by one half, which equation should be used? A. t 1/2 = 1/(k[A] o ) B. t 1/2 = ln2/k C. [A] t = -kt + [A] o D. 1/[A] t = kt + 1/[A] o E. Rate = k[a] 6 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

7 18. In general, to calculate the activation energy for an elementary step given the rate constants at two different temperatures, which equation should be used? A. ln([a] t /[A] o ) = kt B. t 1/2 = ln2/k C. ln(k 1 /k 2 ) = E a /R((T 1 T 2 )/T 1 T 2 ) D. 1/[A] t = kt + 1/[A] o E. Rate = k[a] 19. The Arrhenius equation is k = Ae Ea/RT. The slope of a plot of ln k vs. 1/T is equal to A. k B. k C. E a D. E a /R E. A 20. What is the slope of an Arrhenius plot for the following reaction? 2NOCl 2NO + Cl 2 A K B K C K D K E. not enough information to calculate the slope 21. At 30 C, by how much is a reaction's activation energy decreased by the addition of a catalyst if the catalyst triples the reaction rate? A kj/mol B. 274 J/mol C J/mol D. 119 J/mol E kj/mol 7 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

8 22. Given that E a for a certain biological reaction is 48 kj/mol and that the rate constant is s 1 at 15 C, what is the rate constant at 37 C? A s 1 B s 1 C s 1 D s 1 E. 1.1 s For the chemical reaction system described by the diagram below, which statement is true? A. The forward reaction is endothermic. B. The activation energy for the forward reaction is greater than the activation energy for the reverse reaction. C. At equilibrium, the activation energy for the forward reaction is equal to the activation energy for the reverse reaction. D. The activation energy for the reverse reaction is greater than the activation energy for the forward reaction. E. The reverse reaction is exothermic. 8 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

9 24. For the chemical reaction system described by the diagram below, which statement is true? If the E a for the forward reaction is 25 kj/mol and the enthalpy of reaction is 95 kj/mol, what is E a for the reverse reaction? A. 120 kj/mol B. 70 kj/mol C. 95 kj/mol D. 25 kj/mol E. 70 kj/mol 25. When the concentrations of reactant molecules are increased, the rate of reaction increases. The best explanation for this phenomenon is that as the reactant concentration increases, A. the average kinetic energy of molecules increases. B. the frequency of molecular collisions increases. C. the rate constant increases. D. the activation energy increases. E. the order of reaction increases. 9 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

10 26. The following mechanism has been suggested for the reaction: Identify the molecularity of the rate determining step. A. unimolecular B. bimolecular C. termolecular D. unimolecular and bimolecular E. bimolecular and termolecular 27. The rate law for the reaction 2NO 2 + O 3 N 2 O 5 + O 2 is rate = k[no 2 ][O 3 ]. Which one of the following mechanisms is consistent with this rate law? A. NO 2 + NO 2 N 2 O 4 N 2 O 4 + O 3 N 2 O 5 + O 2 (fast) (slow) B. NO 2 + O 3 NO 5 (fast) NO 5 + NO 5 N 2 O / 2 O 2 (slow) C. NO 2 + O 3 NO 3 + O 2 NO 3 + NO 2 N 2 O 5 (slow) (fast) D. NO 2 + NO 2 N 2 O 2 + O 2 N 2 O 2 + O 3 N 2 O 5 (slow) (fast) 10 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

11 28. Which of the following elementary steps is bimolecular? A. 2A + B A 2 B B. 3B B 2 + B C. A + B + C AB + C D. A 2 2A E. 2A A 2 11 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

12 29. With respect to the figure below, which choice correctly identifies all the numbered positions? A. A B. B C. C D. D E. E 30. The activation energy of a certain uncatalyzed reaction is 64 kj/mol. In the presence of a catalyst, the E a is 55 kj/mol. How many times faster is the catalyzed than the uncatalyzed reaction at 400 C? Assume that the frequency factor remains the same. A. 5.0 times B times C. 15 times D. 2.0 times E. 0.2 times 12 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

13 31. At a particular temperature the first-order gas-phase reaction N 2 O 5 2NO / 2 O 2 has a half-life for the disappearance of dinitrogen pentoxide of 5130 s. Suppose atm of N 2 O 5 is introduced into an evacuated 2.00 L flask. What will be the total gas pressure inside the flask after 3.00 hours? A atm B atm C atm D atm E atm 32. A nuclear stress test utilizes a gamma-emitting radioisotope such as thallium-201 to follow the flow of blood through the heart first at rest, and then under stress. The first-order rate constant for the decay of thallium-201 is 9.5 x 10 3 hr 1. Calculate how long it takes for the amount of thallium-201 to fall to 5.0% of its original value. A. 320 hr B. 340 hr C. 360 hr D. 380 hr E. None of the above 33. Use the table of data shown below to calculate the average rate of the reaction A B between 10 s and 20 s. A M/s B M/s C M/s D M/s E. none of the above 13 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

14 34. What is the rate law that corresponds to the data shown for the reaction 2A + B C? A. Rate = k[b] 0 B. Rate = k[b] 2 C. Rate = k[b] 3 D. Rate = k[b] E. None of the above 35. At a certain temperature, the data below were collected for the reaction below. 2ICl + H 2 I 2 + 2HCl. Determine the rate law for the reaction. A. rate = k[icl][h 2 ] 2 B. rate = k[icl] 2 [H 2 ] C. rate = k[icl][h 2 ] D. rate = k[icl] 2 [H 2 ] 2 E. None of the above 14 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

15 36. At a certain temperature, the data below were collected for the reaction below. 2ICl + H 2 I 2 + 2HCl. Determine the rate constant for the reaction. A L/mol s B L/mol s C L/mol s D L/mol s E. None of the above 37. The rate constant for the first-order decomposition of C 4 H 8 at 500 C is s 1. How long will it take for 10.0% of a M sample of C 4 H 8 to decompose at 500 C? A. 11 s B. 14 s C. 18 s D. 22 s E. None of the above 38. Hydrogen peroxide decomposes to water and oxygen gas, and the activation energy for this process is 42 kj/mol. The hydrogen peroxide formed in biological processes is harmful to tissue, but the enzyme catalase catalyzes the decomposition of hydrogen peroxide by lowering the activation energy to 7.0 kj/mol. Assuming the frequency factor is the same for both processes and independent of temperature, calculate the temperature required for the uncatalyzed decomposition to proceed at the same rate as the enzyme-catalyzed decomposition at 37 C (normal human body temperature). A C B C C C D C E. None of the above 15 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

16 39. Select True or False: It is possible for the following overall reaction to consist of a one step mechanism: 2A + B + C products True False 40. Select True or False: B is a catalyst in the following mechanism: True False 16 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

17 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40 Key 1. B 2. B 3. C 4. B 5. C 6. D 7. B 8. D 9. E 10. D 11. C 12. E 13. B 14. D 15. D 16. B 17. B 18. C 19. D 20. C 21. A 22. C 23. D 24. A 25. B 26. B 27. C 1 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40

18 28. E 29. D 30. A 31. A 32. A 33. E 34. B 35. C 36. C 37. A 38. C 39. FALSE 40. FALSE 2 CHEM Chapter 14. Chemical Kinetics (Homework) Ky40