Practice Exam

1. (10 pts) The figure on the left illustrates the challenges to an environmental chemist. (a) Using acid rain as your illustration, discuss where as a result of a chemical reaction, SO 2, the pollutant/contaminant can affect an ecosystem. The points to emphasize here are (1) that SO 2 itself is not a problem until it is oxidized to H 2 SO 4 : SO 2  SO 3  H 2 SO 4 The acid will change the pH in aquatic systems resulting in fish kills, or affecting trees, particularly those at high elevations in low-lying clouds.

(b ) Using indoor air, discuss briefly, how a pollutant/contaminant can affect human health (Any of the pollutants we discussed in class will be acceptable). Whether you are talking about asbestos, smoke, or radon, some discussion of cancer. There are differences in how the pollutant causes the cancer whether radioactivity (radon) or physical fibers (asbestos).

(5 pts) Complete the table below that shows the atomic effects as a function of energy/wavelength RegionAtomic Effects Microwave Infrared Visible Ultra-violet X-ray,  -ray

(5 pts) Complete the table below that shows the atomic effects as a function of energy/wavelength RegionAtomic Effects MicrowaveRotation InfraredVibration VisibleElectronic excitation Ultra-violetBond-breaking X-ray,  -ray Bond-breaking

( 10 pts) List two concerns that have resulted from the destruction of the ozone layer in the stratosphere. What I am looking for here is a discussion involving cataracts, skin cancer, or amphibian decline. Discussion must include an increasing of UV-B radiation as a result of ozone loss.

(15 pts) One of the compounds believed responsible for the destruction of the ozone layer, is CF 2 Cl 2 Show a series of reactions beginning with the photolysis of CF 2 Cl 2 that would result in the destruction of ozone (CF 2 Cl > CF 2 Cl + Cl). O 3 + Cl  ClO + O 2 ClO + O  Cl + O 2 List two sources of CFCs. Refrigerants, cleaning solvents, blowing agents Write a chemical reaction that could remove Cl from the stratosphere. CH 4 + Cl  HCl + CH 3 or Cl + Cl  Cl 2

(15 pts) Explain what causes the ozone hole to appear and why it occurs in late October/early November (Be as specific as possible, using chemical reactions).  Earth turns – and Antarctic region gets cold and has no sunlight  HNO 3.3H 2 O precipitates out.  HCl and ClONO 2 undergo transformation to HOCl and Cl 2  Earth turns, UV light appears, HOCl  OCl + H or HO + Cl  Also, Cl 2  2 Cl  Destruction begins.  Earth Continues to turn: HNO 3 melts, UV cleaves HNO 3 and OCl is taken out of the system

(10 pts) A compound, methyl bromide, CH 3 Br, used by regional strawberry farmers has been placed on a list to be eliminated by 2005 because of concern about ozone depletion. Please explain. Concern about methyl bromide getting up into the stratosphere and causing the destruction of ozone. CH 3 Br --  CH 3 + Br Br + O 3  BrO + O 2 BrO + O  O 2 + Br

(15 pts) The main compound responsible for acid rain is SO 2 emission. Explain why it is a problem down wind, and not in the immediate vicinity of where it is released. SO 2 is oxidized to H 2 SO 4 and this is a slow oxidation-reduction reaction requiring time to occur, resulting in the sulfuric acid to be created a long distance from the source. List two ways in which SO 2 emission can reduced/eliminated. Conversion to another product (scrubber), dilution, or remove as an impurity. List three effects resulting from acid rain. Vegetation, natural waters, health, or structure damage

(10 pts) One of the major regional concerns is nitrogen deposition as a result of the increasing swine population in SE North Carolina. Discuss this concern and how it can be abated, other than reducing the swine population. Nitrogen deposition from the atmosphere resulting in a nutrient overload causing algal bloom and fish kills. This effect can be mitigated by changing the lagoon system for treating the hog waste.

What conditions must exist for a city to have the potential problem of photochemical smog? Show, using chemical reactions, why we monitor the presence of ozone in the troposphere to indicate pollution. Conditions for photochemical smog are: Stagnant air NO x and VOCs High temperatures Sunlight N 2 + O > 2 NO(Combustion) 2 NO + O 2 NO 2 (rev. rx. slow) NO 2 -h NO+ O (UV-A, UV-B) [Sum of NO 2 and NO given as NO x ] O + O 2 ---M---> O 3 O 3 ---h, O 2 * + O * [Both in ground states or excited states, UV-B radiation is required to dissociate ozone into O * (excited state)] O * + H 2 O -----> 2 OH {Must be in excited state to overcome repulsion}

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