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Ch.14 - Chemical Kinetics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.14 - Chemical KineticsProblema 124
Capitolo 14, Problema 124

The NOx waste stream from automobile exhaust includes species such as NO and NO2. Catalysts that convert these species to N2 are desirable to reduce air pollution. Design a spectroscopic experiment to monitor the conversion of NOx into N2, describing what wavelengths of light need to be monitored as a function of time.

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Identify the absorption spectra of NO and NO2: Use a spectrophotometer to determine the specific wavelengths at which NO and NO2 absorb light. This typically involves scanning a range of wavelengths and recording the absorbance to identify peaks corresponding to these molecules.
Determine the absorption spectrum of N2: Since N2 is a diatomic molecule with a triple bond, it does not have a strong absorption in the UV-visible range. However, you can confirm this by checking its spectrum to ensure it does not interfere with the monitoring of NO and NO2.
Set up the spectroscopic experiment: Use a reaction chamber where the NOx gases are exposed to the catalyst. Connect this chamber to a spectrophotometer that can continuously monitor the absorbance at the identified wavelengths for NO and NO2.
Monitor the change in absorbance over time: As the reaction proceeds, measure the absorbance at the specific wavelengths for NO and NO2. A decrease in absorbance at these wavelengths indicates the conversion of NOx to N2.
Analyze the data: Plot the absorbance versus time for NO and NO2. The decrease in absorbance over time will show the rate of conversion of NOx to N2, allowing you to assess the efficiency of the catalyst.

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Spectroscopy

Spectroscopy is a technique used to measure the interaction of light with matter. It involves analyzing the light emitted, absorbed, or scattered by substances to identify their composition and concentration. In the context of monitoring NOx conversion, specific wavelengths corresponding to the absorption characteristics of NO, NO2, and N2 must be measured to track the reaction progress.
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Molecular Formula via Combustion Example

Wavelengths of Light

Different chemical species absorb light at specific wavelengths, which are determined by their electronic transitions. For NO and NO2, the relevant wavelengths typically fall within the ultraviolet and visible regions of the spectrum. Monitoring these wavelengths allows for the detection of the presence and concentration of these gases during the conversion process to N2.
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Frequency-Wavelength Relationship

Catalytic Conversion

Catalytic conversion refers to the process where a catalyst facilitates a chemical reaction, often lowering the activation energy required. In the case of NOx reduction, catalysts such as platinum or palladium can convert NO and NO2 into N2, a less harmful gas. Understanding the kinetics of this reaction is essential for designing an effective spectroscopic experiment to monitor the conversion over time.
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Conversion Factors
Pratica correlata
Domanda del libro di testo

Many primary amines, RNH2, where R is a carboncontaining fragment such as CH3, CH3CH2, and so on, undergo reactions where the transition state is tetrahedral. (a) Draw a hybrid orbital picture to visualize the bonding at the nitrogen in a primary amine (just use a C atom for 'R').

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