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Ch.14 - Chemical Kinetics
All textbooksBrown 14th EditionCh.14 - Chemical KineticsProblem 80c
Chapter 14, Problem 80c

The addition of NO accelerates the decomposition of N2O, possibly by the following mechanism:
NO(g) + N2O(g) → N2(g) + NO2(g)
2 NO2(g) → 2 NO(g) + O2(g)
(c) If experiments show that during the decomposition of N2O, NO2 does not accumulate in measurable quantities, does this rule out the proposed mechanism?

Verified step by step guidance
1
Understand the proposed mechanism: The mechanism consists of two steps. The first step is the reaction between NO and N2O to form N2 and NO2. The second step involves the decomposition of NO2 to regenerate NO and produce O2.
Consider the experimental observation: It is noted that NO2 does not accumulate in measurable quantities during the decomposition of N2O.
Analyze the implication of NO2 not accumulating: If NO2 does not accumulate, it suggests that NO2 is being consumed as quickly as it is being produced. This implies that the second step of the mechanism, where NO2 decomposes back to NO and O2, is very fast.
Evaluate the compatibility of the mechanism with the observation: The proposed mechanism can still be valid if the second step is much faster than the first step, ensuring that NO2 does not build up in the reaction mixture.
Conclude whether the mechanism is ruled out: The absence of NO2 accumulation does not necessarily rule out the proposed mechanism. It suggests that the second step is rapid, which is consistent with the mechanism as long as NO2 is consumed quickly after its formation.

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 by which reactants are converted into products. It includes elementary steps that detail how bonds are broken and formed. Understanding the proposed mechanism is crucial for analyzing how intermediates, like NO2, are produced and consumed during the reaction.
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Reaction Mechanism Overview

Intermediates

Intermediates are species that are formed during the reaction mechanism but are not present in the final products. They are typically unstable and can quickly convert to other products. In this case, the lack of measurable NO2 accumulation suggests that it may not be a stable intermediate, which is important for evaluating the validity of the proposed mechanism.
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Reaction Mechanism Example

Rate of Reaction

The rate of reaction refers to the speed at which reactants are converted into products. It can be influenced by various factors, including the presence of catalysts or intermediates. If NO2 does not accumulate, it may indicate that the reaction is proceeding rapidly enough that NO2 is consumed as quickly as it is formed, which is a key consideration in assessing the proposed mechanism.
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Related Practice
Textbook Question

The addition of NO accelerates the decomposition of N2O, possibly by the following mechanism: NO1g2 + N2O1g2¡N21g2 + NO21g2 2 NO21g2¡2 NO1g2 + O21g2 (b) Is NO serving as a catalyst or an intermediate in this reaction?

Textbook Question

Many metallic catalysts, particularly the precious-metal ones, are often deposited as very thin films on a substance of high surface area per unit mass, such as alumina (Al2O3) or silica (SiO2). (b) How does the surface area affect the rate of reaction?