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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Step 1: First, we need to calculate the energy of a photon of light with a wavelength of 335 nm. We can use the equation E = hc/λ, where E is the energy, 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. Remember to convert the wavelength from nm to m by multiplying by 1 x 10^-9.

Step 2: The energy obtained in step 1 will be in Joules. However, the question asks for the energy in kJ/mol. To convert the energy from Joules to kJ/mol, we need to use Avogadro's number (6.022 x 10^23 mol^-1). Multiply the energy obtained in step 1 by Avogadro's number and divide by 1000 to convert from Joules to kJ.

Step 3: The energy calculated in step 2 is the maximum energy that can be absorbed by a molecule of formaldehyde to break a bond. This energy corresponds to the maximum strength of a bond that can be broken by absorption of a photon of 335-nm light.

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Key Concepts

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

Photon Energy

The energy of a photon is directly related to its wavelength, described by the equation E = hc/λ, where E is energy, h is Planck's constant, c is the speed of light, and λ is the wavelength. For a photon with a wavelength of 335 nm, this relationship allows us to calculate the energy absorbed when the photon is absorbed by a molecule, which can lead to bond dissociation.

Bond Dissociation Energy

Bond dissociation energy is the amount of energy required to break a specific bond in a molecule, resulting in the formation of separate atoms or radicals. It is typically expressed in kJ/mol and is a critical factor in understanding how much energy is needed to initiate chemical reactions, such as the photodissociation of formaldehyde.

Photodissociation

Photodissociation is the process by which a chemical bond is broken due to the absorption of light, resulting in the formation of reactive species. In the context of formaldehyde, the absorption of a photon can provide enough energy to break the C-H bond, leading to the production of carbonyl (CHO) and hydrogen (H) radicals, which are significant in atmospheric chemistry and smog formation.

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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.

Textbook Question

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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Textbook Question

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 reaction is 420 nm. (b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light?