Textbook Question
Ozone in the upper atmosphere can be destroyed by the following two-step mechanism:
Cl(g) + O3(g) → ClO(g) + O2(g)
ClO(g) + O(g) → Cl(g) + O2(g)
(b) What is the catalyst in the reaction?
Ch.14 - Chemical Kinetics
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement146
- Ch.2 - Atoms, Molecules, and Ions200
- Ch.3 - Chemical Reactions and Reaction Stoichiometry176
- Ch.4 - Reactions in Aqueous Solution155
- Ch.5 - Thermochemistry126
- Ch.6 - Electronic Structure of Atoms131
- Ch.7 - Periodic Properties of the Elements126
- Ch.8 - Basic Concepts of Chemical Bonding123
- Ch.9 - Molecular Geometry and Bonding Theories143
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces91
- Ch.12 - Solids and Modern Materials122
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics174
- Ch.15 - Chemical Equilibrium101
- Ch.16 - Acid-Base Equilibria139
- Ch.17 - Additional Aspects of Aqueous Equilibria146
- Ch.18 - Chemistry of the Environment72
- Ch.19 - Chemical Thermodynamics129
- Ch.20 - Electrochemistry142
- Ch.21 - Nuclear Chemistry101
- Ch.22 - Chemistry of the Nonmetals68
- Ch.23 - Transition Metals and Coordination Chemistry66
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry10
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
Chapter 14, Problem 107d
The following mechanism has been proposed for the reaction of NO with H2 to form N2O and H2O:
NO(g) + NO(g) → N2O2(g)
N2O2(g) + H2(g) → N2O(g) + H2O(g)
(d) The observed rate law is rate = k[NO]2[H2]. If the proposed mechanism is correct, what can we conclude about the relative speeds of the first and second reactions?
Verified step by step guidance1
Identify the overall reaction from the given mechanism: 2NO(g) + H2(g) -> N2O(g) + H2O(g).
Examine the proposed mechanism: Step 1: 2NO(g) -> N2O2(g), Step 2: N2O2(g) + H2(g) -> N2O(g) + H2O(g).
Analyze the rate law: rate = k[NO]^2[H2]. This suggests that the rate-determining step involves two NO molecules and one H2 molecule.
Compare the rate law with the mechanism: The rate law matches the stoichiometry of the first step, indicating that the first step is the slow, rate-determining step.
Conclude that the first reaction (formation of N2O2) is slower than the second reaction (formation of N2O and H2O), as the rate law is determined by the first step.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reaction Mechanism
A reaction mechanism is a step-by-step description of the pathway through which reactants are converted into products. It outlines individual elementary steps, each with its own rate, and helps in understanding how the overall reaction occurs. In this case, the proposed mechanism involves two steps leading to the formation of N2O and H2O from NO and H2.
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Reaction Mechanism Overview
Rate Law
The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is determined experimentally and can provide insights into the mechanism of the reaction. The given rate law, rate = k[NO]^4[H2]^2, indicates that the rate depends on the concentrations of NO and H2, suggesting that the first step is likely the rate-determining step.
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Rate-Determining Step
The rate-determining step is the slowest step in a reaction mechanism that controls the overall rate of the reaction. It is crucial for understanding the kinetics of the reaction. In this scenario, if the observed rate law corresponds to the concentrations of reactants in the first step, it implies that this step is slower than the second step, thus determining the overall reaction rate.
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Related Practice
Textbook Question
Ozone in the upper atmosphere can be destroyed by the following two-step mechanism:
Cl(g) + O3(g) → ClO(g) + O2(g)
ClO(g) + O(g) → Cl(g) + O2(g)
(a) What is the overall equation for this process?
Textbook Question
The following mechanism has been proposed for the reaction of NO with H2 to form N2O and H2O:
NO(g) + NO(g) → N2O2(g)
N2O2(g) + H2(g) → N2O(g) + H2O(g)
(a) Show that the elementary reactions of the proposed mechanism add to provide a balanced equation for the reaction.
Textbook Question
The gas-phase decomposition of ozone is thought to occur by the following two-step mechanism.
Step 1: O3(g) ⇌ O2(g) + O(g) (fast)
Step 2: O(g) + O3(g) → 2 O2 (slow)
(a) Write the balanced equation for the overall reaction.
Textbook Question
At 28 C, raw milk sours in 4.0 h but takes 48 h to sour in a refrigerator at 5 C. Estimate the activation energy in kJ>mol for the reaction that leads to the souring of milk.