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13 • Chemical Kinetics R A T E L A W

 1. What are the units for the corresponding reactions: zero-order, first-order, second-order, and third-order

reaction?

2. On which of the following properties does the rate constant of a reaction depend? a. Reactant concentrations b. Nature of reactants c. Temperature

3. The rate of the reaction 𝐶𝐻!𝐶𝑂𝑂𝐶!𝐻! 𝑎𝑞 + 𝐻!𝑂 𝑙 → 𝐶𝐻!𝐶𝑂𝑂𝐻 𝑎𝑞 + 𝐶!𝐻!𝑂𝐻 𝑎𝑞 shows first-

order characteristics, that is, 𝑟𝑎𝑡𝑒 = [𝐶𝐻!𝐶𝑂𝑂𝐶!𝐻!], even though this is a second-order reaction (first order in 𝐶𝐻!𝐶𝑂𝑂𝐶!𝐻! and first order in 𝐻!𝑂). Explain.

4. The reaction of peroxydisulfate ion (𝑆!𝑂!!!) with iodide ion (𝐼!) is written below.

𝑆!𝑂!!! 𝑎𝑞 + 3𝐼! 𝑎𝑞 → 2𝑆𝑂!!! 𝑎𝑞 + 𝐼!!(𝑎𝑞) From the following data collected at a certain temperature, determine the rate law and calculate the rate constant.

5. The rate law for the reaction 𝑁𝐻!! 𝑎𝑞 + 𝑁𝑂!! 𝑎𝑞 → 𝑁! 𝑔 + 2𝐻!𝑂(𝑙) is given by

𝑟𝑎𝑡𝑒 = 𝑘 𝑁𝐻!! [𝑁𝑂!!] at 25℃. At 25℃, the rate constant (k) is 3.0×10!!  1 𝑀s. Calculate the rate of the reaction at this temperature if 𝑁𝐻!! = 0.26  𝑀 and 𝑁𝑂!! = 0.080  𝑀.

6. Use the data in Table 13.2 (page 573) to calculate the rate of the reaction at the time when 𝐹! =0.010  𝑀 and 𝐶𝑙𝑂! = 0.020  𝑀.

7. Consider the reaction 𝐴 + 𝐵 → 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠. From the data shown to the right, obtained at a certain temperature, determine the order of the reaction and calculate the rate constant:

8. Consider the reaction 𝑋 + 𝑌 → 𝑍. From the data shown to the right, obtained at 360 K, (a) determine the order of the reaction, and (b) determine the initial rate of disappearance of X when the concentration of X is 0.30M and that of Y is 0.040M.

9. Determine the overall orders of the reactions to which the

following rate laws apply: a. 𝑟𝑎𝑡𝑒 = 𝑘[𝑁𝑂!]! b. 𝑟𝑎𝑡𝑒 = 𝑘

c. 𝑟𝑎𝑡𝑒 = 𝑘 𝐻! [𝐵𝑟!]!!

d. 𝑟𝑎𝑡𝑒 = 𝑘[𝑁𝑂]![𝑂!]

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10. Consider the reaction 𝐴 → 𝐵. The rate of the reaction is 1.6×10!!  𝑀/𝑠 when the concentration of A is 0.35 M. Calculate the rate constant if the reaction is (a) first order in A and (b) second order in A

11. The reaction 2𝐴 + 3𝐵 → 𝐶 is first order with respect to A and B. When the initial concentrations are 𝐴 = 1.6×10!!  𝑀 and 𝐵 = 2.4×10!!  𝑀, the rate is 4.1×10!!  𝑀/𝑠. Calculate the rate constant of

the reaction.

12. Consider the reaction: 2 NO(g) + O2(g) → 2 NO2(g) The following data were obtained from three experiments using the method of initial rates:

Initial [NO] M Initial [O2] M Initial rate NO M/s Experiment 1 0.010 0.010 2.5 x 10-5 Experiment 2 0.020 0.010 1.0 x 10-4 Experiment 3 0.010 0.020 5.0 x 10-5

a. Determine the order of the reaction for each reactant. b. Write the rate equation for the reaction. c. Calculate the rate constant. d. Calculate the rate at the instant when [NO] = 0.015 M and [O2] = 0.0050 M e. At the instant when NO is reacting at the rate 1.0 x 10-4 M, what is the rate at which O2 is

reactant and NO2 is forming?

13. The reaction 2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g) was studied at 904 °C, and the data in the table were collected.

Initial [NO] M Initial [H2] M Initial rate N2 M/s Experiment 1 0.420 0.122 0.136 Experiment 2 0.210 0.122 0.0339 Experiment 3 0.210 0.244 0.0678 Experiment 4 0.105 0.488 0.0339

a. Determine the order of the reaction for each reactant. b. Write the rate equation for the reaction. c. Calculate the rate constant at 904 °C. d. Find the rate of appearance of N2 at the instant when [NO] = 0.350 M and [H2] = 0.205 M.

14. The reaction of tbutyl-bromide (CH3)3CBr with water is represented by the equation:

(CH3)3CBr + H2O → (CH3)3COH + HBr The following data were obtained from three experiments using the method of initial rates:

Initial [(CH3)3CBr] M Initial [H2O] M Initial rate M/min Experiment 1 5.0 x 10-2 2.0 x 10-2 2.0 x 10-6 Experiment 2 5.0 x 10-2 4.0 x 10-2 2.0 x 10-6 Experiment 3 1.0 x 10-1 4.0 x 10-2 4.0 x 10-6

a. What is the order with respect to (CH3)3CBr? b. What is the order with respect to H2O? c. What is the overall order of the reaction? d. Write the rate equation. e. Calculate the rate constant, k, for the reaction.