Kinetics (Ch 15) 1. For the reaction: A + 3B 2C a. If at some point the rate of production of C is 0.24 M/s, what is the rate of change of B? b. The following data was collected for this reaction at 25 ˚C. What is the differential rate law? Expt 1 2 3 [A]0 0.10 0.10 0.20 [B]0 0.10 0.20 0.10 c. What is the overall order of the reaction? d. What is the rate constant? Initial rate (M/s) 1.2 x 10-4 4.8 x 10-4 2.4 x 10-4 Kinetics (Ch 15) 2. Given the following data for the reaction: 2A + B + C D + 3E Determine the differential rate law. Expt [A]0 [B]0 [C]0 Initial rate (mol/L s) 1 0.020 0.010 0.020 0.0050 2 0.040 0.010 0.020 0.0100 3 0.020 0.010 0.060 0.0050 4 0.040 0.040 0.020 0.160 Kinetics (Ch 15) Kinetics (Ch 15) 3. The decomposition of nitrogen dioxide, 2 NO2 2NO + O2, obeys the rate law rate = k[NO2]2. For this reaction the rate constant, k = 1.8 x 10-2 L/mol s at 500 K. If the initial concentration of NO2 is 1.2 M, how long will it take for the concentration to decrease by 25%? Kinetics (Ch 15) 4. The thermal decomposition of phosphine, PH3, into phosphorous 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 70 sec? Kinetics (Ch 15) 5. The successive half-lives for a certain reaction were measured to be 10, 20 and 40 minutes. If the initial concentration of the reactant was 1.0 M, how much was left after 80 min of reaction time? Kinetics (Ch 15) 6. Given the following mechanism: H2O2 H2O + O O + CF2Cl2 ClO + CF2Cl ClO + O3 Cl + 2O2 Cl + CF2Cl CF2Cl2 a. Write the overall reaction. b. Identify any intermediate(s). c. Identify any catalyst. d. Write the rate law for each step. Kinetics (Ch 15) 7. For the following reaction, the rate law was determined to be r = k [NO]2 [O2] 2 NO + O2 2 NO2 Determine whether or not the following mechanisms are consistent with this rate law. a. NO + O2 NO2 + O slow O + NO NO2 fast b. NO + O2 NO3 fast equilibrium NO3 + NO 2NO2 slow Kinetics (Ch 15) 8. The forward activation energy for a reaction is 60 kJ/mol. If ΔE for the reaction is 45 kJ/mol, what is the activation energy for the reverse reaction? Kinetics (Ch 15) 9. What factors affect the rate constant for a reaction? Kinetics (Ch 15) 10. The rate constants for a certain second order reaction are 3.20 x 10-2 1/M s at 24 ˚C and 9.45 x 10-1 1/M s at 150 ˚C. a. Calculate the activation energy for the reaction. b. What is the rate constant at 100 ˚C? Kinetics (Ch 15) Bonus Q: How would the addition of a catalyst change the energy values in #8?
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