Chapter 14 Problem Set 1. The initial concentration of H2O2 is XXXXXXXXXXM and 12s later the concentration is XXXXXXXXXXM. What is the initial rate (M/s) of this reaction? 2. The initial concentration...

Chemistry Problem Set


Chapter 14 Problem Set 1. The initial concentration of H2O2 is 0.1108 M and 12s later the concentration is 0.1060 M. What is the initial rate (M/s) of this reaction? 2. The initial concentration of H2O2 is 0.2546 M, and the initial rate of reaction is 9.32 x 10-4 M s-1. What will be [H2O2] at t = 35 s. 3. The rate of the following reaction in aqueous solution is monitored by measuring the number of moles of HgCl2 that precipitate per liter per minute. The data obtained are listed in the table. 2 HgCl2 + C2O42- → 2 Cl- + 2 CO2 + HgCl2 (s) Experiment [HgCl2], M [C2O4]2-, M Initial rate, M/min 1 0.105 0.15 1.8 x 10-5 2 0.105 0.30 7.1 x 10-5 3 0.052 0.30 3.5 x 10-5 4 0.052 0.15 8.9 x 10-6 a. Determine the order of the reaction with respect to HgCl2, with respect to C2O42-, and overall. b. What is the value of the rate constant k? c. What would be the initial rate of reaction if [HgCl2] = 0.20 M and [C2O42-] = 0.22 4. The rate of the following reaction in aqueous solution is monitored by measuring the rate of formation of I3-. Data obtained are listed in the table. S2O82- + 3 I- → 2 SO42- + I3- Experiment [S2O82-]M [I-] M Initial rate, M s-1 1 0.038 0.060 1.4 x 10-5 2 0.076 0.060 2.8 x 10-5 3 0.076 0.120 5.6 x 10-5 a. Determine the order of the reaction with respect to S2O82-, with respect to I-, and overall. b. What is the value of the rate constant k? c. What would be the initial rate of reaction if [S2O82-] = 0.025 M and [I-] = 0.045 M? 5. The first order decomposition of H2O2 (aq) has a rate constant of 3.66 x 10-3 s-1 and the initial concentration of H2O2 is 0.882 M. a. Determine the time at which [H2O2] = 0.600 M. b. Determine the concentration of [H2O2] after 225 s. 6. The half-life for the first-order decomposition of sulfuryl chloride at 320 °C is 8.75 hours. SOCl2 (g) → SO2 (g) + Cl2 (g) a. What is the value of the rate constant k (in hours)? b. What is the pressure of sulfuryl chloride 3.00 hours after the start of the reaction if its initial pressure is 722 mmHg? c. How long after the start of the reaction will the pressure of sulfuryl chloride become 125 mmHg? 7. The rate constant for the second-order decomposition of HI at 700 K is k = 1.2 x 10-3 M-1 s-1. a. In a reaction in which [HI]0 = 0.56 M, what will [HI] be at t = 2.00 hour? b. At what time will [HI]=0.28 M for the reaction? 8. It takes 55 s for [A] to fall to 0.40 M from an initial [A] = 0.80 M in a reaction with rate = k [A]2, what is the rate constant (k) for the reaction. 9. The decomposition of nitramide, NH2NO2, is a first-order reaction. NH2NO2 (aq) → H2O (l) + N2O (g) The rate law is rate = k [NH2NO2] with k = 5.62 x 10-3 min-1 at 15°C. Starting with 0.105 M NH2NO2. a. At what time will [NH2NO2] = 0.0250 M? b. What is [NH2NO2] after 6.00 h? 10. A reaction that is second order in reactant A has [A]0 =0.200 M. The half life is 45.6 sec. What is [A] after 3.00 min? 11. Rate constants for the first-order decomposition of acetonedicarboxylic acid are k = 4.75 x 10-4 s-1 at 293 K and k = 1.63 x 10-3 s-1 at 303 K CO(CH2COOH)2 (aq) . → CO(CH3)2 (aq) + 2 CO2 (g) Acetone dicarboxylic acid acetone What is the activation energy, Ea,of this reaction? 12. The decomposition of ethylene oxide at 652 K is a first order reaction with k = 0.0120 min-1 and an activation energy of 218 kJ/mol. (CH2)2O (g) → CH4 (g) + CO (g) a. Calculate the rate constant of the reaction at 525 K. b. Calculate the temperature at which the rate constant k= 0.0100 min-1. 13. The following is proposed as a plausible reaction mechanism: A + B → I (slow) I + B → C + D (fast) a. What is the net reaction described by this mechanism? b. What is a plausible rate law for the reaction? 14. For the reaction: H2(g) + I2 (g) → 2 HI (g), a proposed mechanism is: Fast step : I2 → 2 I Slow Step: 2 I + H2 → 2 HI What is the net equation based on this mechanism? 15. The following mechanism has been proposed for a reaction. S2O82- + I- → IS2O83- (slow) IS2O83- → 2 SO42- + I+ (fast) I+ + I- → I2 (fast) I2 + I- → I3- (fast) Write the balanced equation for the net reaction and give the overall rate law based on this mechanism. 16. The elementary steps that make up a reaction are shown below. NO2 (g) + F2 (g) → NO2F (g) + F(g) (slow) F(g) + NO2(g) → NO2F (g) (fast) a. Using the elementary steps, determine the overall reaction. b. The overall reaction was found to have the following rate law: rate = k [NO2] [F2]. Is this rate law consistent with the proposed mechanism (elementary steps)? c. Identify any intermediates. 17. The overall reaction for the NO2 oxidation of CO is shown below. The experimentally determined rate law is: rate = k [NO2]2 NO2 (g) + CO (g) → NO (g) + CO2 (g) (overall reaction) A student proposes the following mechanism for the reaction (1 elementary step). NO2 (g) + CO (g) → NO (g) + CO2 (g) (rate determining step, only step) Is the student’s proposed mechanism consistent with the rate law? Explain.