Chapter 16 Chemical Kinetics Homework Questions and Problems 1. Complete the following statements relating to the production of ammonia by the Haber process, for which the overall reaction is N2(g) + 3H2(g) Æ 2NH3(g). a) The rate of decomposition of N2 is _______ times the rate of decomposition of H2. b) The rate of formation of NH3 is ______ times the rate of decomposition of H2. c) The rate of formation of NH3 is ______ times the rate of decomposition of N2. d) If the rate of ammonia production is 2.7 x 10-3 mol/Lsec. What is the rate of reaction of H2? 2. Manganate ions, MnO42-(aq), form permanganate ions and manganese(IV)oxide in an acidic solutions at a rate of 2.0 mol/Lmin according to the reaction: 3 MnO42-(aq) + 4 H+(aq) Æ 2 MnO4-(aq) + MnO2(s) + 2 H2O(l) a) What is the rate of formation of permaganate ions? b) What is the rate of reaction of H+(aq) ions? 3. The reaction between bromate ions and bromide ions in acidic solution is given by the equation BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) Æ 3 Br2(l) + 3 H2O(l) a) Given the results from four experiments, determine the orders for all three reactants, the overall order, and the average value of the specific rate constant. Initial Initial Initial Measured [BrO3-] [Br-] [H+] Initial Rate Exp. (mol/L) (mol/L) (mol/L) (mol/L sec) 1 0.10 0.10 0.10 8.0 x 10-4 2 0.20 0.10 0.10 1.6 x 10-3 3 0.10 0.20 0.10 3.2 x 10-3 4 0.10 0.10 0.20 3.2 x 10-3 b) What will the initial rate of the reaction be if the initial [BrO3-] = 0.30 mol/L, [Br-] = 0.30 mol/L, and [H+] = 0.30 mol/L?4. The rate of the reaction between hemoglobin (Hb) and carbon monoxide (CO) was studied at 20oC. The following data were collected with all concentration units in µmol/L. (A hemoglobin concentation of 2.21 µmol/L is equal to 2.21 x 10-6 mol/L.) [Hb]o [CO]o Initial Rate (µmol/L) (µmol/L) (µmol/L sec) 2.21 1.00 0.619 4.42 1.00 1.24 4.42 3.00 3.71 a) Determine the orders of this reaction with respect to Hb and CO. b) Determine the rate law. c) Calculate the value of the rate constant. d) What would be the initial rate for an experiment with [Hb]o = 3.36 µmol/L and [CO]o = 2.40 µmol/L? 5. The decomposition of hydrogen peroxide was studied, and the following data were obtained at a particular temperature: Time (s) [H2O2] (mol/L) 0 1.00 120 0.91 300 0.78 600 0.59 1200 0.37 1800 0.22 2400 0.13 3000 0.082 3600 0.050 Manipulate the data above and make any appropriate graphs to determine the rate law, the integrated rate law, the value of the reaction constant and the half life of the reaction. Calculate the [H2O2] at 4000 sec after the start of the reaction. 6. Experimental values for the temperature dependence of the rate constant for the gas phase nitrogen monoxide catalyzed breakdown of the ozone to oxygen: NO + O3 Æ NO2 + O2 Temperature (oC) k (L/mol sec) -78 1.08 x 109 -43 2.95 x 109 -13 5.42 x 109 25 12.0 x 10996 35.5 x 109 Manipulate the data and make the appropriate graph, and determine the activation energy for this reaction.7. One mechanism for the destruction of ozone in the upper atmosphere is O3(g) + NO(g) Æ NO2(g) + O2(g) Slow NO2(g) + O(g) Æ NO(g) + O2(g) Fast Overall reaction: O3(g) + O(g) Æ 2O2(g) a) Which species is a catalyst? b) Which species is an intermediate? c) Eact for the uncatalyzed reaction O3(g) + O(g) Æ 2O2(g) is 14.0kJ/mol. Eact for the same reaction when catalyzed is 11.9 kJ/mol. What is the ratio of the rate constant for the catalyzed reaction to that for the uncatalyzed reaction at 25oC? Assume that the frequency factor A is the same for each reaction. d) One of the concerns about the use of Freons is that they migrate to the upper atmosphere, where the chlorine atoms can be generated by the following reaction: hν CCl2F2 CF2Cl + Cl Freon-12 Chlorine atoms can act as a catalyst for the destruction of ozone. The activation energy for the reaction Cl + O3 Æ ClO + O2 is 2.1 kJ/mol. What is the ratio of the rate constant for the catalyzed reaction to that for the uncatalyzed reaction at 25oC? Again assume that the frequency factor A is the same for each reaction. Which is the more effective catalyst for the destruction of ozone? How many more times