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ENC702S - ENVIRONMENTAL CHEMISTRY - 1ST OPP - NOVEMBER 2024 |
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nAmlBIA UnlVERSITY
OF SCIEnCEAnD TECHnOLOGY
Facultyof Health,Natural
ResourcaensdApplied
Sciences
Schoolof NaturalandApplied
Sciences
Departmentof Biology,
ChemistryandPhysics
13JacicsonKauJeuaStreet T: +2E4612072012
Private Bi:5 133-98
F: +2E4612079012
Windhoek
E: dbcp@n11sr.na
~lAMIBIA
W:www.nust.na
QUALIFICATION : BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
COURSE:ENVIRONMENTAL CHEMISTRY
DATE: NOVEMBER 2024
DURATION: 3 HOURS
LEVEL: 7
COURSECODE: ENC702S
SESSION: 1
MARKS: 100
EXAMINER:
MODERATOR:
FIRST OPPORTUNITY: EXAMINATION QUESTION PAPER
Mr Tjaronda Karumendu, Mr Festus Shafodino
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.
s. Mark all answers clearly with their respective question numbers.
PERMISSIBLE MATERIALS
1. Non-Programmable Calculator
This paper consists of 3 pages including this front page and Periodic table.
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Question 1
[30]
1.1. Define the following terms
(6)
a. Geology:
b. Geochemistry
c. Environmental geochemistry
1.2. Explain the variations of temperature with altitude in different layers of the
atmosphere.
(2)
1.3. The mechanism by which the earth self regulates its temperature is called the carbon
dioxide cycle. Explain how the CO2 geochemical cycle illustrates the definition of
environmental chemistry.
{10) .
1.4. Briefly explain what Earth's Natural Capital is and what it provides to ensure life on Earth
(4)
1.5. It is encouraged that economic systems must emphasize provision of services rather
than material goods that deplete resources. Suggest two ways in which the above can
be achieved.
(2)
1.6. Briefly describe the Goldschmidt's geochemical classifications of elements.
(6)
Question 2
[20]
2.1. What is stratospheric ozone depletion?
(2)
2.2. Describe how and where (tropic level) nitric oxide is responsible for the destruction of
ozone. Show reactions and the sources of all reactants involved.
(5)
2.4. A fly ash particle emitted into the atmosphere reaches altitude of 500 m. The fly ash
particle has density of 0.8 g cm-3 and falls at 1 m s-1. Below is Stokes' law equation for
sedimentation.
a. Taking the density of air as 1.2 g L-1, air viscosity as 170.8x10- 6 g cm-1s-1, and
acceleration due to gravity as 9.8 m s-2, calculate the effective diameter of the fly
ash particle. Would this particulate be classified as one of the six priority pollutants
regulated by USEPA.Justify your answer
(10)
b. Considering the maximum altitude the particle can reach, estimate the residence
time, of this particulate matter in the atmosphere.
(3)
Environmental Chemistry (ENC702S)
pt Opportunity November 2024 2
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Question 3
[25)
3.1. Define the following terms
a. Evapotranspiration
(1)
b. Thermal stratification
(2)
c. Oxygen saga curve
(1)
3.2. Consider the unique and important properties of water. Describe each of the following
unique properties of water related to
a. High heat of evaporation
(2)
b. Transmission of light (transparency)
(2)
c. High surface tension
(2)
d. Excellent solvent
(2)
3.3. Water with an alkalinity of2.00 x 10-3 equivalents/liter has a pH of 7.00. Calculate [CO2],
[HCQ3-],[Cai-], and [OH-J,
(8)
3.4. State the balanced reaction and the bacteria that is involved in catalysing the oxidation
of Fe {II) to Fe {Ill).
(3)
Question 4
[25)
4.1. Differentiate between phytoremediation and cation exchange
(2)
4.2. What does AMO stand for, and what is the general balanced equation for this process?
(3)
4.3. How does water naturally accumulate dissolved solids, and why is evaporation
considered as the main cause of salinity problems?
(3)
4.4. It is well known that the sorption properties of clay minerals and humus usually are pH
dependent. Give 3 examples (with reactions) demonstrating the pH dependency of these
materials.
(6)
4.5. State four (4) processes through which the soil can modify the water chemistry and/or
water quality.
(4)
4.6. State three (3) the negative environmental impacts of volcanoes into the geosphere,
biosphere, and atmosphere.
(3)
4.7. Why is the geosphere regarded as a source of natural capital?
(3)
***** END OF QUESTIONPAPER*****
Environmental Chemistry (ENC702S)
ist Opportunity November 2024 3