Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photochemical smog: CH2O + hn → CHO + H. The maximum wavelength of light that can cause this reaction is 335 nm. (c) Compare your answer from part (b) to the appropriate value from Table 8.3. What do you conclude about the C−H bond energy in formaldehyde?

Verified step by step guidance

Step 1: Understand the photodissociation reaction given: CH2O + hn → CHO + H. This reaction involves breaking a bond in formaldehyde using light energy.

Step 2: Recognize that the maximum wavelength of light that can cause this reaction is 335 nm. This wavelength corresponds to the energy required to break the bond.

Step 3: Use the equation for energy of a photon, E = (hc)/λ, where h is Planck's constant (6.626 x 10^-34 J·s), c is the speed of light (3.00 x 10^8 m/s), and λ is the wavelength in meters. Convert 335 nm to meters by multiplying by 10^-9.

Step 4: Calculate the energy of the photon using the formula from Step 3. This energy represents the minimum energy required to break the C−H bond in formaldehyde.

Step 5: Compare the calculated energy to the bond energy values provided in Table 8.3. If the calculated energy is close to the bond energy of a C−H bond, it suggests that the photodissociation involves breaking a C−H bond in formaldehyde.

Key Concepts

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

Photodissociation

Photodissociation is the process by which a chemical compound breaks down into smaller components upon absorbing light. In the context of formaldehyde (CH2O), it absorbs photons of a specific wavelength (335 nm) to dissociate into CHO and H. Understanding this process is crucial for analyzing how light energy can influence chemical reactions and the formation of pollutants like photochemical smog.

Bond Energy

Bond energy refers to the amount of energy required to break a bond between two atoms in a molecule. In formaldehyde, the C−H bond energy is significant because it determines the stability of the molecule and its reactivity under light exposure. By comparing the calculated bond energy with known values, one can infer the strength of the C−H bond and its implications for the formation of products during photodissociation.

Photochemical Smog

Photochemical smog is a type of air pollution that results from the reaction of sunlight with pollutants such as volatile organic compounds and nitrogen oxides. The formation of formaldehyde from alcohol-based fuels contributes to this phenomenon, as its photodissociation leads to the generation of reactive species that can further react to form secondary pollutants. Understanding the relationship between these reactions and smog formation is essential for evaluating environmental impacts.

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Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH₂O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH₂O + hn ¡ CHO + H The maximum wavelength of light that can cause this reaction is 335 nm. (b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 335-nm light?

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Textbook Question

Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH2O + hn ¡ CHO + H The maximum wavelength of light that can cause this reac- tion is 335 nm. (d) Write out the formaldehyde photodis- sociation reaction, showing Lewis-dot structures.

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An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reac- tion is 420 nm. (a) In what part of the electromagnetic spec- trum is light with this wavelength found?

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