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. (b) Using a resource such as Table 8.3, look up the energies of the bonds in these molecules. In what region of the electromagnetic spectrum do these energies lie?

Verified step by step guidance

Step 1: Identify the bonds present in the molecules NO and NO2. NO has a nitrogen-oxygen single bond, while NO2 has one nitrogen-oxygen single bond and one nitrogen-oxygen double bond.

Step 2: Use a resource such as Table 8.3 to find the bond dissociation energies for the N-O single bond and the N=O double bond. These values are typically given in kilojoules per mole (kJ/mol).

Step 3: Convert the bond dissociation energies from kJ/mol to energy per bond in joules. This can be done by dividing the energy in kJ/mol by Avogadro's number (6.022 x 10^23 mol^-1) to get the energy in joules per bond.

Step 4: Convert the energy per bond from joules to electronvolts (eV) using the conversion factor 1 eV = 1.602 x 10^-19 J.

Step 5: Determine the region of the electromagnetic spectrum that corresponds to the calculated energy in eV. Compare the energy values to the known ranges of the electromagnetic spectrum, such as infrared, visible, ultraviolet, etc.

Key Concepts

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

Bond Energies

Bond energy is the amount of energy required to break a bond between two atoms in a molecule. It is a crucial concept in understanding the stability of molecules and the energy changes that occur during chemical reactions. For NO and NO2, knowing the bond energies helps predict how much energy is needed to convert these nitrogen oxides into nitrogen gas (N2) through catalytic processes.

Electromagnetic Spectrum

The electromagnetic spectrum encompasses all types of electromagnetic radiation, ranging from radio waves to gamma rays. Each type of radiation has a specific wavelength and energy associated with it. Understanding where the bond energies of NO and NO2 lie within this spectrum is essential for determining the type of radiation that can be used to break these bonds, which is relevant in the context of catalysis and pollution control.

Catalysis

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which is not consumed in the reaction. In the context of NOx reduction, catalysts facilitate the conversion of nitrogen oxides into less harmful nitrogen gas, often by providing an alternative reaction pathway with lower activation energy. Understanding the role of catalysts is vital for developing effective strategies to reduce air pollution from automobile exhaust.

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Catalyzed vs. Uncatalyzed Reactions

Related Practice

Textbook Question

The rates of many atmospheric reactions are accelerated by the absorption of light by one of the reactants. For example, consider the reaction between methane and chlorine to produce methyl chloride and hydrogen chloride:

Reaction 1: CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g)

This reaction is very slow in the absence of light. However, Cl₂(g) can absorb light to form Cl atoms:

Reaction 2: Cl₂(g) + hv → 2 Cl(g)

Once the Cl atoms are generated, they can catalyze the reaction of CH₄ and Cl₂, according to the following proposed mechanism:

Reaction 3: CH₄(g) + Cl(g) → CH₃(g) + HCl(g)

Reaction 4: CH₃(g) + Cl₂(g) → CH₃Cl(g) + Cl(g)

The enthalpy changes and activation energies for these two reactions are tabulated as follows:

Reaction ΔH° (kJ/mol) E_a (kJ/mol)

3 +4 17

4 -109 4

(b) By using the data tabulated here, sketch a quantitative energy profile for the catalyzed reaction represented by reactions 3 and 4.

Textbook Question

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').