Ch.14 - Chemical Kinetics

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.14 - Chemical Kinetics

Problem 46

Chapter 14, Problem 46

The relative rates of the reaction A + B S AB in vessels(1)–(3) are 4:4:1. Red spheres represent A molecules, andblue spheres represent B molecules.(1)-(3)
(a) What is the order of the reaction in A and B?

Verified step by step guidance

Identify the number of A and B molecules in each vessel. Vessel 1: 2 A and 3 B, Vessel 2: 4 A and 3 B, Vessel 3: 3 A and 2 B.

Note the given relative rates of the reaction in vessels 1, 2, and 3, which are 4:4:1.

Set up the rate law expression for the reaction: rate = k[A]^m[B]^n.

Compare the rates and concentrations between vessels to determine the reaction order. For example, compare vessels 1 and 2 to find the order with respect to A, and compare vessels 1 and 3 to find the order with respect to B.

Solve the equations derived from the comparisons to find the values of m and n, which represent the order of the reaction with respect to A and B, respectively.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reaction Order

The reaction order refers to the power to which the concentration of a reactant is raised in the rate law of a chemical reaction. It indicates how the rate of reaction is affected by the concentration of reactants. For example, a first-order reaction in A means that doubling the concentration of A will double the reaction rate, while a second-order reaction means that doubling A will quadruple the rate.

Rate Law

The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is typically written in the form Rate = k[A]^m[B]^n, where k is the rate constant, and m and n are the orders of the reaction with respect to reactants A and B, respectively. Understanding the rate law is crucial for determining how changes in concentration affect the reaction rate.

Stoichiometry of the Reaction

Stoichiometry involves the quantitative relationships between the reactants and products in a chemical reaction. In this case, the stoichiometry of the reaction A + B → AB can help determine the relative amounts of A and B that react. The given rates of reaction in different vessels can be analyzed to infer the stoichiometric coefficients, which are essential for deducing the order of the reaction in A and B.

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Related Practice

Textbook Question

What is the molecularity of each of the following elementary reactions?(a)

Draw a plausible transition state for the bimolecular reaction of nitric oxide with ozone. Use dashed lines to indicate the atoms that are weakly linked together in the transition state. NO(g) + O3(g) NO2(g) + O2(g)

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Textbook Question

Consider a reaction that occurs by the following mechanism:

A + BC → AC + B

AC + D → A + CD

The potential energy profile for this reaction is as follows:

(d) Is the reaction endothermic or exothermic? Add labels to the diagram that show the values of the energy of reaction ΔE and the activation energy Ea for the overall reaction.

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Textbook Question

The following pictures represent the progress of a reaction in which two A molecules combine to give a more complex molecule A2, 2 AS A2.

(b) What is the rate law?

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Textbook Question

Consider the first-order reaction AS B in which A molecules(red spheres) are converted to B molecules (blue spheres).

(a) Given the pictures at t = 0 min and t = 1 min, drawpictures that show the number of A and B moleculespresent at t = 2 min and t = 3 min.

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