Mechanisms and Molecularity7 of 18<>I Review | Constants | Periodic TableOrder and rate law of a reactionLearning Goal:To understand how elementary steps make up amechanism and how the rate law for an elementarystep can be determined.The overall order of an elementary step directly corresponds to its molecularity. Both steps in this example are second order because theyare each bimolecular. Furthermore, the rate law can be determined directly from the number of each type of molecule in an elementarystep. For example, the rate law for step 1 isVery often, a reaction does not tell us the whole story.For instance, the reactionrate = k[NO2]²The exponent "2" is used because the reaction involves two NO2 molecules. The rate law for step 2 isNO2(9) + CO(9)→NO(g)+ CO2(g)rate = k[NO3]"[coj = k[NO3][C0]does not involve a collision between an NO2molecule and a CO molecule. Based on experimentaldata at moderate temperatures, this reaction isthought to occur in the following two steps:because the reaction involves only one molecule of each reactant the exponents are omitted.1. NO2(9) + NO2(g)→NO3(g) + NO(g)2. NO3(9) + C0(g)→CO2(g) + NO2(9)Analyzing a new reactionConsider the following elementary steps that make up the mechanism of a certain reaction:Each individual step is called an elementary step.Together, these elementary steps are called thereaction mechanism.1. 3X-E +F2. E + M F+ NOverall, the resulting reaction isPart ANO2(g) + CO(9)→NO(g)+CO2(9)Notice that in the elementary steps NO3 appears

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Answered: Analyzing a new reaction Consider the…

Analyzing a new reaction Consider the following elementary steps that make up the mechanism of a certain reaction: 1. 3X->E +F 2. E + MF+N Bart 0

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter11: Chemical Kinetics: Rates Of Reactions

Section: Chapter Questions

Problem 115QRT

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Consider a reaction of the type aA products, in which the rate law is found to he rate = k[A]3 (termolecular reactions are improbable but possible). If the first half-tife of the reaction is found to he 40. s, what is the time for the second half-life? Hint: Using your calculus knowledge, derive the integrated rate law from the differential rate law for a tennolecular reaction: Rate=d[A]dt=k[A]3
The rate of photodecomposition of the herbicide piclo- ram in aqueous systems was determined by exposure to sunlight for a number of days. One such experiment produced the following results. (Data from R.T. Hedlun and C.R. Youngson, “The Rates of Photodecomposition of Picloram in Aqueous Systems," Fate of Organic Pesticides in tbe Aquatic Environment, Advances in Chemistry Series, #111, American Chemical Society (1972), 159—172.) Exposure Time, t (days) [Pidoram] (mol L_1) 0 4.14 X 10-6 7 3.70 X 10-6 14 3.31 X 10-6 21 2.94 X 10~6 28 2.61 X 10~6 35 2.30 X 10-6 42 2.05 X 10-6 49 1.82 X 10"6 56 1.65 X 10-6 Determine the order of reaction, the rate constant, and the half-life for the photodecomposition of picloram.
. find the rate law predicted for a particular reaction mechanism.
For the past 10 years, the unsaturated hydrocarbon 1, 3-butadiene (CH2 = CH - CH = CH2) has ranked 38th among the top 50 industrial Chemicals. It is used primarily for the manufacture of synthetic rubber. An isomer exists also as cyclobutene: The isomerization of cyclobutene to butadiene is first-order and the rate constant has been measured as 2.0104s1 at 150 C in a 0.53-L ?ask. Determine the partial pressure of cyclobutene and its concentration after 30.0 minutes if an isomerization reaction is carried out at 150 C with an initial pressure of 55 torr.
a Suggest a mechanism for the bromination of ethane: Br2+CH3CH3CH3CH2Br+HBr b Would you expect that this reaction might go faster or slower than the chlorination of methane? Hint: Consider the strengths of the bonds involved in the initial steps of the mechanism.
Nitroglycerine is an extremely sensitive explosive. In a series of carefully controlled experiments, samples of the explosive were heated to 160 C and their first-order decomposition studied. Determine the average rate constants for each experiment using the following data: Initial [C3H5N3O9] (M) 4.88 3.52 2.29 1.81 5.33 4.05 2.95 1.72 t (s) 300 300 300 300 180 180 180 180 %Decomposed 52.0 52.9 53.2 53.9 34.6 35.9 36.0 35.4
The hydrolysis of the sugar sucrose to the sugars glucose and fructose, C12H22O11+H2OC6H12O6+C6H12O6 follows a first-order rate equation for the disappearance of sucrose: Rate =k[C12H22O11] (The products of the reaction, glucose and fructose, have the same molecular formulas but differ in the arrangement of the atoms in their molecules.) (a) In neutral solution, k=2.11011s1 at 27 C and 8.51011s1 at 37 C. Determine the activation energy, the frequency factor, and the rate constant for this equation at 47 C (assuming the kinetics remain consistent with the Arrhenius equation at this temperature). (b) When a solution of sucrose with an initial concentration of 0.150 M reaches equilibrium, the concentration of sucrose is 1.65107M . How long will it take the solution to reach equilibrium at 27 C in the absence of a catalyst? Because the concentration of sucrose at equilibrium is so low, assume that the reaction is irreversible. (c) Why does assuming that the reaction is irreversible simplify the calculation in pan (b)?
Pyrolysis involves heating compounds to break them into smaller molecules, and typically involves free-radical chain reactions. Pyrolysis of crude oil fractions is a common method of making smaller hydrocarbons from large-chain hydrocarbons. Pyrolysis of ethane, C2H6, forms ethylene and hydrogen gases C2H4 and H2 as the primary products. Suggest a mechanism for this pyrolysis reaction, labeling your reactions as initiation, propagation, and termination steps.