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ENC702S-ENVIRONMENTAL CHEMISTRY-JAN 2020 |
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6
NAMIBIA UNIVERSITY
OF SCIENCE AND TECHNOLOGY
FACULTY OF HEALTH AND APPLIED SCIENCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 7
COURSE NAME: ENVIRONMENTAL CHEMISTRY | COURSE CODE: ENC702S
SESSION: JANUARY 2020
DURATION: 3 HOURS
PAPER: THEORY
MARKS: 100
SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION PAPER
EXAMINER(S) | Dr JULIEN LUSILAO
MOpDERATOR: | Dr JAMES ABAH
INSTRUCTIONS
1. Answer ALL the questions in the answer book provided.
2. Write and number your answers clearly.
3. All written work MUST be done in blue or black ink.
PERMISSIBLE MATERIALS
Non-programmable Calculators
THIS QUESTION PAPER CONSISTS OF 5 PAGES (Including this front page)
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Question 1
[15]
1.1 The following figure illustrates the definition of Environmental Chemistry with respect to
the five spheres of the Earth system.
O
WSs,
SOi3 + 1/2+ 0H,;0 — H,SO,
Atmosphere
S(co+ a O2l>)SO: =>
1 Anthros phere
VU VAY ULEN
VVVV AVN
W\\wWy\\uHsu)uSvOy4yqy14
\\V\\ ULVA LA\\Y\\
vWiiVaAAvN vyA \\
Explain in detail what is described in this figure.
(4)
1.2 It is well known that the biosphere strongly influences the other spheres of the Earth
system as shown in the figure below.
Aquatic plants
Water-dwelling Aquatic plants
animals
Cyclization of biomass and
nutrients in ecosystems
Name the processes represented in the figure by A to D with respect to the above
statement.
(5)
1.3 It is said that Industrial ecology views an industrial system like an industrial
ecosystem. Briefly explain this approach in three points.
(6)
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Question 2
[30]
2.1 Briefly discuss the following aspects of the troposphere: atmospheric location, major
source of heat, major gaseous components, mass, and temperature gradient.
(5)
2.2 What phenomenon is responsible for the maximum temperature observed at the
boundary between the stratosphere and the mesosphere?
(2)
2.3 Give the BALANCED chemical reactions involving oxygen molecule in the following
reactions:
(a) Ozone formation
(1)
(b) Animal respiration
(1)
(c) Combustion of fossil fuel
(1)
2.4 Air pollutants may be classified based on the way they reach the atmosphere.
Describe (with an example for each case) the different classes of pollutants that fall
within this category.
(6)
2.5 What is the settling velocity of a particle having a Stokes’ diameter of 10 um anda
density of 1 g/cm? in air at 1.00 atm pressure and 0°C temperature?
The viscosity of air at O°C is 170.8 micropoise (poise = g/cm.S) and the density of air
under these conditions is 1.29 g/L. (g = 9.81 m/sec’)
(5)
2.6 (a) What is stratospheric ozone depletion?
(2)
(b) Describe, with appropriate reactions, how the depletion in (a) occurs using
chlorofluorocarbon (CFC) as a starting point.
(4)
(c) List the different solutions that are currently used as an ADAPTATION
approach to the global warming problem.
(3)
Question 3
[30]
3.1 Define the following:
(a) Evapotranspiration
(1)
(b) Infiltration
(1)
(c) Runoff
(1)
3.2 Write the approximate net reaction between carbonate ion and water in a system
that is exposed to atmospheric carbon dioxide. Is the resulting water mildly acidic or
mildly alkaline?
(2)
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3.3 (a) Differentiate between Total Alkalinity and Phenolphthalein Alkalinity.
(2)
(b) For a solution having 1.00 x 10° equivalents/liter total alkalinity (i.e. contributions
from HCO3", CO3*, and OH’) at [H*] = 4.69 x 10°74, what is the percentage
contribution to alkalinity from CO37?
(5)
3.4 (a) Provide the mathematical relationship between pE and the oxidation-reduction
potential, E, at 25°C for E values measured in volts.
(1)
(b) How would you expect pE to vary with depth in a stratified lake?
(2)
(c) Upon what half-reaction is the rigorous definition of pE based?
(2)
3.5 Give the main role of the following microorganisms in aquatic environments:
(a) Algae
(1)
(b) Fungi
(1)
(c) Protozoa
(1)
3.6 (a) Provide the likely source of the following water pollutants:
(i) Herbicides
(1)
(ii) Fecal coliform bacteria
(1)
(iii) Pharmaceutical metabolites
(1)
(b) What is water eutrophication and why is it considered as a case of pollution?
(5)
(c) What are the most harmful elemental pollutants found in waters?
(2)
Question 4
[25]
4.1 Provide four examples showing the interconnection between the biosphere and the
geosphere.
(4)
4.2 Give the general chemical formula of the following minerals:
(a) Quartz
(1)
(b) Calcite (limestone)
(1)
(c) Magnetite
(1)
(d) Halite
(1)
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4.3 What does the geosphere provide to the environment as a source of natural capital? (3)
4.4 What are the main size groups of soil and how are they formed?
(5)
4.5 Match the following:
(A) Metamorphic rock; (B) Chemical sedimentary Rocks; (C) Detrital rock; (D) Organic
sedimentary rock.
(1) Produced by the precipitation or coagulation of dissolved or colloidal weathering
products; (2) Contain residues of plant and animal remains; (3) Formed from action
of heat and pressure on sedimentary rocks; (4) Formed from solid particles eroded
from igneous rocks as a consequence of weathering.
(4)
4.6 (a) What are soil fumigants?
(1)
(b) What are the four major categories of concern with respect to pesticides and their
residues in soil?
(4)
END