Wright CHM 1220 - CHM 1220_Kinetics_Fall2017_answers (2 pages)

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CHM 1220 ANSWERS 1 In Class Activity Kinetics Fall 2017 The reaction of hydroxyl radical with ozone HO2 g O3 g OH g 2 O2 g is a rapid second order reaction The rate of reaction was measured in milliseconds for different OH 2 concentrations in the presence of a large excess of O3 Time ms HO2 M O3 M 0 2 28 10 6 1 00 10 3 10 2 07 10 6 1 00 10 3 6 20 1 86 10 1 00 10 3 6 30 1 71 10 1 00 10 3 6 80 1 00 10 1 00 10 3 From this data a plot of ln HO2 versus time has a slope of 0 0103 and an intercept of 12 991 What is the pseudo first order rate constant and what is the second order rate constant Note You could approximate the pseudo firstActual Rate law order rate constant using HO2 and time from the table however you CANNOT use them to figure Rate k HO2 O3 overall second order out the second order rate constant However experimental conditions make it pseudo first order Rate k HO2 Where k k O3 0 Integrated rate law for a first order reaction Given in problem ln HO2 k t ln HO2 0 ln HO2 0 0103 t 12 991 Therefore pseudo first order rate constant k 0 0103 ms 1 Second order rate constant can be determined directly based on previous statements k k O3 0 2 The reaction k k 0 0103 ms 1 10 3 M 1 ms 1 3 O3 0 1 00 10 M CO g NO2 g CO2 g NO g was studied at 25 C and the following data were obtained Experiment 1 2 3 4 CO 0 M 5 0 10 4 5 0 10 4 1 0 10 3 1 5 10 3 NO2 0 M 0 36 10 4 0 18 10 4 0 36 10 4 0 72 10 4 Initial Rate M hr 3 4 10 8 1 7 10 8 6 8 10 3 a What is the rate law for this reaction at 25 C including the value of the rate constant From Experiments 1 2 CO constant rate halved NO2 halved first order with respect to NO2 From Experiments 1 3 NO2 constant rate doubled CO doubled first order with respect to CO Rate law Rate k CO NO2 Using data from any experiment k b What is the initial rate of the reaction for experiment 4 Rate 3 4 10 8 M hr 1 1 89 M 1hr 1 4 4 CO NO2 5 0 10 M 0 36 10 M Rate k CO NO2 1 89M 1hr 1 1 5 10 3 M 0 72 10 4 2 04 10 7 M hr 2 Given following rate constants determine the activation energy of the decomposition reaction shown below T C CH3CHO CH4 CO k M 1 2 s 1 0