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ENC702S - ENVIRONMENTAL CHEMISTRY - 2ND OPP - JANUARY 2024 |
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nAmlBIA UnlVERSITY
OF SCIEnCEAnOTECHnOLOGY
FacultyofHealthN, atural
ResourceasndApplied
Sciences
Schoolof NaturalandApplied
Sciences
Departmenot f Biology,
ChemistryandPhysics
QUALIFICATION: BACHELORof SCIENCE
QUALIFICATIONCODE: 07BOSC
COURSE:ENVIRONMENTAL CHEMISTRY
DATE: JANUARY 2024
DURATION: 3 HOURS
13JacksonKaujeua Street
Private Bag13388
Windhoek
NAMIBIA
T: +264 612072012
F: +264 61207 9012
E: dbcp@nust.na
W: www.nust.na
LEVEL:7
COURSECODE: ENC702S
SESSION: 1
MARKS: 100
SECOND OPPORTUNITY/ SUPPLEMENTARY: EXAMINATION QUESTION PAPER
EXAMINER:
MODERATOR:
Dr. Mpingana N. Akawa
Prof. James Abah
INSTRUCTIONS
1. Answer all questions on the separate answer sheet.
2. Please write neatly and legibly.
3. Do not use the left side margin of the exam paper. This must be allowed for the
examiner.
4. No books, notes and other additional aids are allowed.
5. Mark all answers clearly with their respective question numbers.
PERMISSIBLE MATERIALS
1. Non-Programmable Calculator
This paper consists of 4 pages including this front page
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QUESTION 1
(20)
a) Use the biogeochemical cycle of sulphur to illustrate the definition of environmental
chemistry.
(10)
· b) Carbon dioxide is one of the greenhouse gases which is largely responsible for global
warming.
i. Explain how carbon dioxide contributes to global warming.
(2)
ii. Discuss4 impacts of global warming on the ecosystem.
(4)
iii. Suggest adaptation approaches to the global warming problem.
(4)
QUESTION 2
(20)
a) With the aid of chemical reactions, explain how acid mine drainage (AMO) is formed.
(10)
b) Discussthe ecological impact of acid mine drainage.
(5)
c) Explain how AMO can be prevented.
(5)
QUESTION 3
(20)
a) Briefly describe the main categories of atmospheric chemical reactions.
(6)
b) What is stratospheric ozone depletion?
(2)
c) Describe, with appropriate reactions, how the depletion in (a) occurs using
chlorofluorocarbon (CFC)as a starting point.
(4)
d) Differentiate between the following terms:
i. Primary and secondary pollutants
(2)
ii. Direct and Indirect sources
(2)
iii. Point and Area sources
(2)
iv. Classical smog and photochemical smog
(2)
QUESTION 4
[20)
a) Discussthe ecological effect of the following and explain how to mitigate.
(15)
i. Eutrophication
ii. Acid rain
iii. Pesticides
iv. Photochemical smog
V. Acid mine drainage
Environmental Chemistry (ENC702S)
2nd Opportunity January 2024
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b) Define soil erosion and name its different types.
(5)
-=Q=U-=ES"-T_'"_'"_I_O_"_'"_"_N_-_-_--_-"_-_5__________
[20]
a) The diagram below shows the thermal water stratification of a lake in summer.
Describe the layers represented in A, B and C and provide their respective key
characteristics in terms of water temperature, dissolved oxygen & its effect on plants and
chemical species.
(8)
b) Considering the following Oxygen sag curve resulting from the addition of oxidizable
pollutant to a stream:
Clean Decomposition Septic Recovery Clean
... , ·y . \\.. , y zone
,.
zone
....
zone
,.
....-.....z..o..n...e,..........\\.i.:.".....z..o.".n.'·.e.......·.......
I
I
I
1 evel oj)oxidizable .1..-.---t
pollutant
I
I
I
I
I
I
I
I
I
' :I
Dissolved I
oxygen I
Time or distance downstream
Discussthe five zones observed in the diagram.
(5)
Environmental Chemistry (ENC702S)
2nd Opportunity January 2024
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c) Write down the two main reactions associated with the formation of acid rain and
explain the ecotoxicological effects of acid rain.
(5)
d) Differentiate between Total Alkalinity and Phenolphthalein Alkalinity.
(2)
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END OF QUESTION PAPER
Environmental Chemistry (ENC702S)
2nd Opportunity January 2024
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