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ENC702S - ENVIRONMENTAL CHEMISTRY - 2ND OPP - JAN 2023 |
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nAm I BI A u n IVE RS ITV
OF SCIEn CE Ano TECHn OLOGY
FACULTYOF HEALTH,NATURAL RESOURCESAND APPLIEDSCIENCES
DEPARTMENTOF NATURALAND APPLIEDSCIENCES
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 7
COURSENAME: ENVIRONMENTAL CHEMISTRY COURSECODE: ENC702S
SESSION:JANUARY 2023
DURATION: 3 HOURS
PAPER:THEORY
MARKS: 100
SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION PAPER
EXAMINER(S) Dr JULIEN LUSILAO
MODERATOR: 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.
PERMISSIBLEMATERIALS
Non-programmable Calculators
THIS QUESTION PAPERCONSISTSOF 4 PAGES(Including this front page)
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Question 1
1.1 The following figure illustrates the definition of Environmental Chemistry with
respect to the five spheres of the Earth system.
[20]
Corboo io
not
Inorganic carbon In
limestone and other rocks
Carbon io the
geospbere
Inorganic and organic carbon lo sediments,
anoxic decay of organic carbon->CO,, CH,
Fossil carbon In fuels
such as conl
Explain in detail what is described in this figure.
{6}
1.2 Briefly discuss the geochemical {Goldschmidt} classification of the elements.
{8}
1.3 Explain the processes that result in the over accumulation of some elements in
localized areas {i.e. formation of ore minerals} with examples.
{6}
Question 2
[30]
2.1 {a) The table below shows the values of the average atmospheric pressure at sea
level with different units.
Unit
1. Torr
2. Atmosphere
3. cm Hg
4. Pascal
5. Bar
6. Psi
Value
A.1
B. 76
C. 14.7
D. 1.01325
E. 760
F. 1.01325 x 105
Associate each unit (1 to 6} to its corresponding value {A to F).
{3)
{b} Give the trade names of the following fluorocarbons
{i) Trichlorofluoromethane {CC/3F)
{1)
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(ii) Dichlorodifluoromethane (CCl2F2)
(1)
(iii) Bromotrifluoromethane (CBrF3)
{1)
2.2 The atmosphere is divided in 4 main regions called troposphere, stratosphere,
mesosphere and thermosphere.
(a) What is the main criterion used for the division of the atmospheric regions?
(2)
(b) It has been reported that while water vapour can range between 1 to 5% in the
troposphere, little water is found in the stratosphere.
(i) What prevents tropospheric water to reach the stratosphere?
{2)
(ii) What is the main source of stratospheric water? Show the reaction involved. (2)
(iii) What is the main purpose of stratospheric water? Show the reaction involved. {2)
2.3 It has been reported that the inorganic oxides are the main gases responsible for
the acidification of rain water. Name three different elements which oxides may
react with to form atmospheric acids and write the corresponding BALANCED
reaction in each case.
(6)
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 Persistent Organic Pollutants (POPs) are poorly biodegradable organic compounds
recognized as especially troublesome. Provide the reasons behind the underlined
statement.
(4)
Question 3
[30]
3.1 Water is an excellent solvent, it has higher heat of evaporation than any other
material (540 cal/g) and has the higher latent heat of fusion (3.33 x 105 J/kg) than any
other liquid (except NH3). Provide the respective environmental significance of the
underlined properties of water.
(6)
3.2 (a) Define water alkalinity.
(2)
(b) Why is the determination of the bicarbonate alkalinity (also called
phenolphthalein alkalinity) is done at pH 8.3?
(2)
(c) For a solution having 1.0 x 10-3 equivalents/liter total alkalinity (i.e. from HCO3-,
co/-, and OH-) at [W] = 4.69 x 10-11, what is the percentage contribution to
alkalinity from co/- (Kai= 4.45 X 10-7 and Ka2= 4.69 X 10-11)?
(4)
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3.3 (a) What are humic substances?
(2)
(b) Differentiate between humin material and fluvic acid.
(2)
(c) Provide two environmental concerns related to the occurrence of humic
substances in freshwater systems.
(2)
3.4 (a) Provide the likely source of the following water pollutants:
(i) Herbicides
(2)
(ii) Fecal coliform bacteria
(2)
(b) Briefly discuss the main environmental concerns associated with the
occurrence of pesticide metabolites and other organic pollutants in water?
(6)
Question 4
[20]
4.1 Define the following terms:
(a) Evaporites
(1)
(b) Weathering
(1)
(c) Clays
(1)
(d) Sediments
(1)
(e) Sublimates
(1)
4.2 What are the main size groups of soil and how are they formed?
(5)
4.3 (a) What are soil macronutrients?
(2)
(b) Provide the main chemical forms of occurrence of the following nutrients in soil:
(i) Carbon
(1)
(ii) Nitrogen
(1)
(iii) Phosphorous
(1)
4.4 Name five surface processes that cause natural hazards in the geosphere.
(5)
END
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