CHEM 122 CHEMICAL KINETICS CHAP 14 ASSIGN PLACE THE LETTER REPRESENTING THE BEST ANSWER TO EACH QUESTION ON THE APPROPRIATE LINE ON THE ANSWER SHEET. FOR OTHER QUESTIONS, CLEARLY WRITE THE ANSWER, INCLUDING UNITS WHEN NECESSARY, ON THE ANSWER SHEET. CLEARLY SHOW ALL WORK ON SCRAP PAPER. HAND IN ASSIGNMENT, ANSWER SHEET, AND SCRAP WORK. 1. A gas chromatograph can be used to determine the relative amounts of reactants and products by A) measuring the changes in pressure as the reaction proceeds. B) analyzing the intensity of the transmitted light. C) separating the components of the mixture, which results in an individual peak for each component and the peaks are quantified. D) measuring the degree of the polarization of light. E) measuring the change in temperature of the reaction. 2. Write a balanced reaction for which the following rate relationships are true. Rate = = = - A) N2 + O2 N2O B) 2 N2O 2 N2 + O2 C) N2O N2 + 2 O2 D) N2O N2 + O2 E) 2 N2 + O2 2 N2O 3. What is the overall order of the following reaction, given the rate law? NO(g) + O3(g) NO2(g) + O2(g) Rate = k[no][o3] A) 1st order B) 2nd order C) 3rd order D) 1 order E) 0th order 4. A rate is equal to 0.0200 M/s. If [A] = 0.100 M and rate = k[a]0[b]2, what is the new rate if the concentration of [A] is increased to 0.200 M? A) 0.0200 M/s B) 0.0400 M/s C) 0.0600 M/s D) 0.0800 M/s E) 0.100 M/s 5. A rate is equal to 0.0200 M/s. If [A] = 0.100 M and rate = k[a]2[b]2, what is the new rate if the concentration of [A] is increased to 0.200 M? A) 0.0200 M/s B) 0.0400 M/s C) 0.0600 M/s D) 0.0800 M/s E) 0.100 M/s 6. Determine the rate law and the value of k for the following reaction using the data provided. CO(g) + Cl2(g) COCl2(g) [CO]i (M) [Cl2]i (M) Initial Rate (M-1s-1) 0.25 0.40 0.696 0.25 0.80 1.97 0.50 0.80 3.94 A) Rate = 11 M-3/2s-1 [CO][Cl2]3/2 B) Rate = 36 M-1.8s-1 [CO][Cl2]2.8 C) Rate = 17 M-2s-1 [CO][Cl2]2 D) Rate = 4.4 M-1/2s-1 [CO][Cl2]1/2 E) Rate = 18 M-3/2s-1 [CO]2[Cl2]1/2 1 P a g e
7. Determine the rate law and the value of k for the following reaction using the data provided. NO 2 (g) + O3(g) NO 3 (g) + O 2 (g) [NO2]i (M) [O3]i (M) Initial Rate (M-1s-1) 0.10 0.33 1.42 0.10 0.66 2.84 0.25 0.66 7.10 A) Rate = 1360 M -2.5 s -1 [NO 2 ] 2.5 [O 3 ] B) Rate = 227 M -2.5 s -1 [NO 2 ][O 3 ] 2.5 C) Rate = 43 M -1 s -1 [NO 2 ][O 3 ] D) Rate = 430 M -2 s -1 [NO 2 ] 2 [O 3 ] E) Rate = 130 M -2 s -1 [NO 2 ][O 3 ] 2 8. Determine the rate law and the value of k for the following reaction using the data provided. 2 NO(g) + O 2 (g) 2 NO 2 (g) [NO]i (M) [O 2 ]i (M) Initial Rate (M -1 s -1 ) 0.030 0.0055 8.55 10-3 0.030 0.0110 1.71 10-2 0.060 0.0055 3.42 10-2 A) Rate = 57 M -1 s -1 [NO][O 2 ] B) Rate = 3.8 M -1/2 s -1 [NO][O 2 ] 1/2 C) Rate = 3.1 10 5 M -3 s -1 [NO] 2 [O 2 ] 2 D) Rate = 1.7 10 3 M -2 s -1 [NO] 2 [O 2 ] E) Rate = 9.4 10 3 M -2 s -1 [NO][O 2 ] 2 9. Which of the following statements is FALSE? A) The average rate of a reaction decreases during a reaction. B) It is not possible to determine the rate of a reaction from its balanced equation. C) The rate of zero-order reactions is not dependent on concentration. D) The half-life of a first-order reaction is dependent on the initial concentration of reactant. E) None of the statements is FALSE. 10. The rate constant for the first-order decomposition of N2O is 3.40 s-1. What is the half-life of the decomposition? A) 0.491 s B) 0.204 s C) 0.236 s D) 0.424 s E) 0.294 s 11. The half-life for the second-order decomposition of HI is 15.4 s when the initial concentration of HI is 0.67 M. What is the rate constant for this reaction? A) 1.0 10-2 M-1s-1 B) 4.5 10-2 M-1s-1 C) 9.7 10-2 M-1s-1 D) 2.2 10-2 M-1s-1 E) 3.8 10-2 M-1s-1 12. The first-order decomposition of N2O at 1000 K has a rate constant of 0.76 s-1. If the initial concentration of N2O is 10.9 M, what is the concentration of N2O after 9.6 s? A) 7.4 10-3 M B) 1.0 10-3 M C) 1.4 10-3 M D) 3.6 10-3 M E) 8.7 10-3 M 13. The first-order decay of radon has a half-life of 3.823 days. How many grams of radon decompose after 5.55 days if the sample initially weighs 100.0 grams? A) 83.4 g B) 16.6 g C) 50.0 g D) 36.6 g E) 63.4 g 2 P a g e
14. The second-order decomposition of NO2 has a rate constant of 0.255 M-1s-1. How much NO2 decomposes in 4.00 s if the initial concentration of NO2 (1.00 L volume) is 1.33 M? A) 1.8 mol B) 0.85 mol C) 0.48 mol D) 0.77 mol E) 0.56 mol 15. For a reaction, what generally happens if the temperature is increased? A) A decrease in k occurs, which results in a faster rate. B) A decrease in k occurs, which results in a slower rate. C) An increase in k occurs, which results in a faster rate. D) An increase in k occurs, which results in a slower rate. E) There is no change with k or the rate. 16. A reaction is followed and found to have a rate constant of 3.36 104 M -1 s -1 at 344 K and a rate constant of 7.69 M -1 s -1 at 219 K. Determine the activation energy for this reaction. A) 23.8 kj/mol B) 42.0 kj/mol C) 11.5 kj/mol D) 12.5 kj/mol E) 58.2 kj/mol 17. If the activation energy for a given compound is found to be 103 kj/mol, with a frequency factor of 4.0 10 13 s -1, what is the rate constant for this reaction at 398 K? A) 1.2 s -1 B) 8.2 s -1 C) 3.9 10 10 s -1 D) 1.7 10 10 s -1 E) 2.5 10 7 s -1 18. Which of the following statements is TRUE? A) The rate constant does not depend on the activation energy for a reaction where the products are lower in energy than the reactants. B) A catalyst raises the activation energy of a reaction. C) Rate constants are temperature dependent. D) The addition of a homogeneous catalyst does not change the activation energy of a given reaction. E) None of the above is true. 19. Identify a heterogeneous catalyst. A) CFCs with ozone B) Pd in H2 gas C) KI dissolved in H2O2 D) H2SO4 with concentrated HCl E) H3PO4 with an alcohol 20. What is the overall order of the following reaction, given the rate law? 2X + 3Y 2Z Rate = k[x]1[y]2 A) 3rd order B) 5th order C) 2nd order D) 1st order E) 0th order 21. In the hydrogenation of double bonds, a catalyst is needed. In the last step, the reactants must escape from the surface into the gas phase. This step is known as A) adsorption. B) diffusion. C) reaction. D) desorption. E) none of the above 22. At one point during an analysis of the reaction shown below, compound W was used up at a rate of 0.4 moll -1 s -1. At what rate was compound Y being formed? 2W + 4X 3Y + 2Z A. 0.2 B. 0.3 C. 0.4 D. 0.6 E. 0.8 23. What is the rate of the reaction described in question 1? A. 0.2 B. 0.3 C. 0.4 D. 0.6 E. 0.8 3 P a g e
Questions 24-26 refer to the following reaction diagram for a chemical reaction with and without a catalyst. 24. In the potential energy diagram shown above, which letter shows the activation energy for the uncatalyzed reaction? 25. In the potential energy diagram shown above, which letter shows the activation energy for the catalyzed reaction? 26. In the potential energy diagram shown above, which letter shows the heat of the reaction? 27. Given the following rate law, how does the rate of reaction change if the concentration of Y is doubled? Rate = k[x] 4 [Y]3 A) The rate of reaction will increase by a factor of 6. B) The rate of reaction will decrease by a factor of 4. C) The rate of reaction will increase by a factor of 8. D) The rate of reaction will increase by a factor of 4. E) The rate of reaction will remain unchanged. 28. If the concentration of a reactant is 6.25%, how many half-lives has it gone through? A) 7 B) 10 C) 3 D) 4 E) 5 29. The rate constant for a first-order reaction is 0.54 s-1. What is the half-life of this reaction if the initial concentration is 0.33 M? A) 0.089 s B) 1.8 s C) 0.31 s D) 5.6 s E) 1.3 s 30. For a particular first-order reaction, it takes 24 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction? A) 2.0 10-4 s-1 B) 9.6 10-4 s-1 C) 1.2 10-2 s-1 D) 5.8 10-2 s-1 31. The second-order reaction 2 Mn(CO)5 Mn2(CO)10, has a rate constant equal to 3.0 109 M-1 s-1 at 25 C. If the initial concentration of Mn(CO)5 is 2.0 10-5 M, how long will it take for 90.% of the reactant to disappear? A) 6.7 10-16 s B) 7.4 10-15 s C) 1.5 10-4 s D) 6.0 10 3 s 32. Given the following proposed mechanism, predict the rate law for the overall reaction. A2 + 2 B 2 AB (overall reaction) Mechanism A2 2 A A + B AB fast slow A) Rate = k[a] 1/2 [B] 2 B) Rate = k[a2][b] C) Rate = k[a2] 2 [B] 1/2 D) Rate = k[a2] 1/2 E) Rate = k[a2]1/2[b] 4 P a g e
EXTRA CREDIT 33. A reaction is found to have an activation energy of 38.0 kj/mol. If the rate constant for this reaction is 1.60 10 2 M -1 s -1 at 249 K, what is the rate constant at 436 K? A) 2.38 10 5 M -1 s -1 B) 1.26 10 3 M -1 s -1 C) 7.94 10 4 M -1 s -1 D) 4.20 10 5 M -1 s -1 E) 3.80 10 4 M -1 s -1 34. In aqueous solution, hypobromite ion, BrO-, reacts to produce bromate ion, BrO3 -, and bromide ion, Br-, according to the following chemical equation. 3 BrO-(aq) BrO3 - (aq) + 2 Br-(aq) A plot of 1/[BrO-] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO- is 0.80 M, how long will it take one-half of the BrO- ion to react? A) 4.5 10-2 s B) 7.1 s C) 12 s D) 22 s 35. Derive an expression for a "1/4-life" for a first-order reaction. A B C D E NAME DATE ANSWER SHEET CHEM 122 CHAP 14 ASSIGN 1. 11. 21. 31. 2. 12. 22. 32. 3. 13. 23. 33. 4. 14. 24. 34. 5. 15. 25. 35. 6. 16. 26. 36. 7. 17. 27. 37. 8. 18. 28. 38. 9. 19. 29. 39. 10. 20. 30. 40. SPRING 2018 5 P a g e