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Kinetics

Kinetics. Chapter 15 E-mail: benzene4president@gmail.com Web-site: http://clas.sa.ucsb.edu/staff/terri/. Kinetics – ch 15. 1. The average rate of disappearance of ozone in the reaction 2 O 3 (g) → 3 O 2 (g)

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Kinetics

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  1. Kinetics

    Chapter 15 E-mail: benzene4president@gmail.com Web-site: http://clas.sa.ucsb.edu/staff/terri/
  2. Kinetics – ch 15 1. The average rate of disappearance of ozone in the reaction 2 O3(g) → 3 O2(g) is found to be 8.9 × 10–3 atm/min. What is the rate of appearance of O2 during this interval?
  3. Kinetics – ch 15 2. The rate law for the following reaction 2NO(g) + O2(g)  2NO2(g) was experimentally found to be in the form: rate=k[NO]x[O2]y It was also found that when the NO concentration was doubled, the rate of the reaction increases by a factor of 4. In addition, when both the O2 and the NO concentration were doubled, the rate increases by a factor of 8. What is the reaction order of O2?
  4. Kinetics – ch 15 2. Consider the following reaction: A + 3 B  2 C a. The following data was collected for this reaction at 25C. What is the rate law? b. What is the overall order for the reaction? c. Calculate the rate constant? d. What is the rate for experiment 4?
  5. Kinetics – ch 15 3. Given the following data for the reaction: 2 A + B  2 C Determine the rate law, the rate constant and the missing concentrations.
  6. Kinetics – ch 15 4. Consider the following reaction: Cl2 (g) + CHCl3 (g)  HCl (g) + CCl4 (g) The rate law for this reaction has been observed to be: Rate = k[Cl2]1/2[CHCl3] What are the units of the rate constant assuming time in seconds?
  7. Kinetics – ch 15 5. What would you have to plot in order to get a straight line for the following: a. Zero order b. First order c. Second order
  8. Kinetics – ch 15 5. Consider the decomposition of nitrogen dioxide: 2 NO2 2 NO + O2 Rate = k[NO2]2 a. What is the integrated rate law? b. A plot of 1/[NO2] verses time yielded a straight line with a slope of 1.8 x 10-3 Lmol-1s-1 at 500 K. If the initial concentration is 1.2 M, how long will it take for the [NO2] to decrease by 38%?
  9. Kinetics – ch 15 6. The thermal decomposition of phosphine (PH3) into phosphorus and hydrogen is a first order reaction. The half-life for this reaction is 35 sec at 680C. a. Calculate the time required for 95% of the phosphine to decompose. b. What fraction of phosphine remains after 78 seconds?
  10. Kinetics – ch 15 7. What happens to the half-lives for zero, first and second order? a. Get longer b. Get shorter c. Stays constant What is the 3rd half life for a second order reaction with k = 0.22 hr-1M-1 with an initial concentration of 12 M.
  11. Kinetics – ch 15 8. For the reaction A  products, successive half-lives are observed to be 20.0, 10.0, and 5.0 min for an experiment in which [A]0 = 0.1 M. What is the concentration of A at 50.0 min?
  12. Kinetics – ch 15 9. Consider two reaction vessels, one containing A and the other containing B, with equal initial concentrations. If both substances decompose by first-order kinetics where ka = 4.5 x 10-4 s-1 and kb = 3.7 x 10-3 s-1; how much time must pass to reach a condition such that [A] = 4.00[B]?
  13. Kinetics – ch 15 10. The rate of the reaction O + NO2 NO + O2 was studied at a certain temperature. a. In one experiment, [NO2] was in large excess at a concentration of 1.0 x 1013 molecules/cm3 when the following data collected. What is the order with respect to the oxygen atoms? b. The reaction is known to be first order with respect to NO2. Determine the overall rate law and the rate constant.
  14. Kinetics – ch 15 11. Given the following mechanism: H2O2 H2O + O O + CF2Cl2 ClO + CF2Cl ClO + O3 Cl + 2 O2 Cl + CF2Cl  CF2Cl2 a. Write the overall equation for the reaction? b. Identify the reaction intermediates. c. Identify the catalyst.
  15. Kinetics – ch 15 12. Write the overall reaction, identify any intermediates and derive a rate law given the following reaction mechanism: Cl2  2 Cl (fast equilibrium) Cl + CHCl3 HCl + CCl3 (slow) Cl + CCl3 CCl4 (fast)
  16. Kinetics – ch 15 13. The following mechanism is proposed for the reduction of NO3- by MoCl62-: k1 MoCl62- MoCl5- + Cl- k-1 k2 OMoCl5- + NO2- NO3- + MoCl5- a. What is the intermediate? b. Derive an expression for the rate law (rate = d[NO2-]/dt) for the overall reaction using steady-state approximation.
  17. Kinetics – ch 15 14. The forward activation energy for an elementary step is 42 kJ/mol and the reverse activation energy is 32 kJ/mol. Calculate E for the step.
  18. Kinetics – ch 15 15. The rate constants of a certain second-order reaction are 3.20x10-2/Ms at 24C and 0.945 /Ms at 150C. a. Calculate the activation energy for this reaction. b. What is the rate constant at 100C?
  19. Kinetics – ch 15 16. The activation energy for the reaction H2 (g) + I2 (g) → 2 HI (g) is changed from 184 kJ/mol to 59.0 kJ/mol both at 600. K by the introduction of a Pt catalyst. Calculate the ratio of the catalyzed rate constant to the un-catalyzed rate constant. Assume A is constant.
  20. Kinetics – ch 15
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