Download Chemistry Homework: Absorption Spectra, Ozone, Nitrogen Dioxide and more Assignments Chemistry in PDF only on Docsity! Atmospheric Chemistry Homework #3 1. The potential energy curves for the S2 molecule are shown below. a. Using these as a guide, sketch out the expected absorption spectrum for S2. Your spectrum should show both "banded" and "continuous" absorption features. Indicate which absorbances will be strong and which weak. b. Using the potential energy curves, at what wavelength will dissociation of S2 to ground state products first be possible? At what wavelength will dissociation of S2 to excited state products be possible? 2. Using the standard atmosphere given on page 951 of your text, determine the number of molecules in the troposphere, stratosphere and total atmosphere. The mean radius of the earth is 6371 km. 5. Nitrogen dioxide undergoes photodissociation for give nitric oxide and an oxygen atom: NO2 + hn Æ NO + O a. Assuming ground state NO is formed, what wavelengths are required to form O(1D) from this reaction? to form O(3P)? Use the enthalpy data on page 943 of your text. b. Using data from Chapter 4 of your text, determine an approximate J-value for this reaction. Do the calculation for the surface of the earth at 40° N. Latitude, September 1, near noon. What is the lifetime of NO2 with respect to photolysis under these conditions? 6. Calculate the 1/e penetration depth for light as a function of wavelength from 150 to 350 nm (every 20 nm). Assume SZA = 0 and the attached standard atmosphere. Use absorption cross sections given above and the ozone column data below. Plot your results as penetration depth vs l. Altitude (km) ozone column (molecules/cm2) 0 9.5(18) 5 9.1(18) 10 8.7(18) 15 8.1(18) 20 6.3(18) 25 3.7(18) 30 1.7(18) 35 5.6(17) 40 1.7(17) 45 5.8(16) 50 2.0(16) 55 7.6(15) 60 2.8(15) 65 9.5(14) 70 3.1(14) 75 1.6(14) 80 1.1(14) 85 6.0(13) 90 1.2(13) 95 2.6(12) 100 1.0(12) 7. Given the absorption cross sections below and assuming a unity quantum yield over all wavelengths, estimate the lifetime of CCl4 at 15, 25 and 40 km. Use the altitude dependent actinic fluxes given in your text. 8. A major volcanic eruption produced an aerosol layer in the stratosphere that was 1 km thick and had a measured optical depth at 500 nm of t=0.2. Assuming the particles are 1 mm in diameter, a. What is the size parameter of the particles? b. How many particles/cm3 are present in the volcanic aerosol layer? 9. Text, Chapter 3, problem 11. (page 84) 10. Text, Chapter 4, problem 3. (page 125) 11. Looking at the spectra of ClO, BrO and IO given on pages 116 and 117 of your text, qualitatively discuss the relative lifetimes of these three molecules. Be sure to justify your ranking.
