Practice Exam

1
Practice Exam
2

• (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, SO2,
  the pollutant/contaminant can affect an
  ecosystem.

The points to emphasize here are (1) that SO2
itself is not a problem until it is oxidized to
H2SO4 SO2 ? SO3 ? H2SO4 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.
3
(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).

4
(5 pts) Complete the table below that shows the
atomic effects as a function of energy/wavelength
Region Atomic Effects
Microwave
Infrared
Visible
Ultra-violet
X-ray, g-ray
5
(5 pts) Complete the table below that shows the
atomic effects as a function of energy/wavelength
Region Atomic Effects
Microwave Rotation
Infrared Vibration
Visible Electronic excitation
Ultra-violet Bond-breaking
X-ray, g-ray Bond-breaking
6
( 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.

7
(15 pts) One of the compounds believed
responsible for the destruction of the ozone
layer, is CF2Cl2

• Show a series of reactions beginning with the
  photolysis of CF2Cl2 that would result in the
  destruction of ozone (CF2Cl2 --l-gt CF2Cl Cl).
• O3 Cl ? ClO O2
• ClO O ? Cl O2
• List two sources of CFCs.
• Refrigerants, cleaning solvents, blowing agents
• Write a chemical reaction that could remove Cl
  from the stratosphere.
• CH4 Cl ? HCl CH3 or Cl
  Cl ? Cl2

8
(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
• HNO3.3H2O precipitates out.
• HCl and ClONO2 undergo transformation to HOCl and
  Cl2
• Earth turns, UV light appears, HOCl ? OCl H or
  HO Cl
• Also, Cl2 ? 2 Cl
• Destruction begins.
• Earth Continues to turn HNO3 melts, UV cleaves
  HNO3 and OCl is taken out of the system

9
(10 pts) A compound, methyl bromide, CH3Br, 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.
• CH3Br --l ? CH3 Br
• Br O3 ? BrO O2
• BrO O ? O2 Br

10
(15 pts) The main compound responsible for acid
rain is SO2 emission.

• Explain why it is a problem down wind, and not in
  the immediate vicinity of where it is released.
• SO2 is oxidized to H2SO4 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 SO2 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

11
(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.

12
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.

• N2 O2 ----gt 2 NO(Combustion)
• 2 NO O2 lt--gt NO2 (rev. rx. slow)
• NO2 -hnlt400 nm-gtNO O
• (UV-A, UV-B)
• Sum of NO2 and NO given as NOx
• O O2 ---M---gt O3
• O3 ---hn, lt320 nm ---gt O2 O
• Both in ground states or excited states, UV-B
  radiation is required to dissociate ozone into
  O(excited state)
• O H2O -----gt 2 OH Must be in excited state
  to overcome repulsion

• Conditions for photochemical smog are
• Stagnant air
• NOx and VOCs
• High temperatures
• Sunlight

13
How did you do?