Part B. Peroxyacyl nitrates contain two relatively weak bonds that can be broken by low-energy photons. The weakest is the N−O bond in the nitrate functional group of the molecule with a standard bond-dissociation energy of 201 kJ / mol. What is the longest wavelength of a photon, in nanometers, that has enough energy to cause the photodissociation of the weakest bond. Assume all energy of the photon is efficiently used for the photodissociation.
Express your answer to three significant figures and include the appropriate units.
Peroxyacyl nitrates (PANs) are secondary pollutants in photochemical smog. Free radical reactions catalyzed by ultraviolet light from the sun oxidize unburned hydrocarbons to aldehydes, ketones, and dicarbonyl compounds, whose secondary reactions create peroxyacyl radicals, which combine with nitrogen dioxide to form peroxyacyl nitrates. These dissociate only slowly into radicals and NO2, which means that they can carry nitrates to sites other than their place or origin to regions in the troposphere where ozone can be produced more readily. Peroxyacyl nitrates are both toxic and irritating and even dissolve more readily in water than ozone. Even a few parts per billion can cause eye irritation and higher concentrations can cause extreme damage to vegetation.
One of the highest concentrations of peroxyacyl nitrates has been found in the Los Angeles (LA) basin at 30.0 mol of peroxyacetyl nitrate per 1 billion moles of air (30 ppb), reaching its peak at mid-afternoon. Most of the pollution in the LA basin is created in an area of only 3000 km2 and the pollution depth below the inversion layer is normally about 500 m. This concentration was therefore found in 1500 km3 of air above Los Angeles.
Frequently Asked Questions
What scientific concept do you need to know in order to solve this problem?
Our tutors have indicated that to solve this problem you will need to apply the The Particle Nature of Light concept. You can view video lessons to learn The Particle Nature of Light. Or if you need more The Particle Nature of Light practice, you can also practice The Particle Nature of Light practice problems.