CHEM 171. QUESTIONS AND ANSWERS.
STUDY MATERIAL. 2024/2025 A+ GRADE
ANSWERS
1 . Which of the three gases constitute most of Earth's
atmosphere? : Nitrogen78%
Oxygen- 21 %
Aragon-I %
C020.04%
2. What range of altitudes constitutes the troposphere?
Stratosphere? : Troposphere- extends from ground level to
15km altitude and contains 85% of earths mass
Stratosphere- protion of atmosphere from 15-50km altitude
3. What atmospheric gas is primarily responsible for filtering
sunlight in the 120-220 nm range? Which, if any, absorbs most
of the Sun's rays in th e222-320 nm range? Which absorbs
primarily in the 320-400 nm range?: oxygen-120-220nm 03-
222-320nm
N02- 320-400nm
4. What is the game given to the finite packets of light absorbed
by matter? : UV-B
5. What is photochemically dissociated: atoms and molecules that
absorb light immediately undergo a change in the organization of
their electrons
6. Equation for ozone is formed in the stratosphere.: O + 02 -> 03
+ Heat
7. Two reaction that contribute to ozone destruction.: 03 + UV
photon (»<326m)
02 + O
03 + o 202
8. What two steps destroy ozone in the middle and upper
stratosphere?: Cl +
1/5
, CHEM 171. QUESTIONS AND ANSWERS.
STUDY MATERIAL. 2024/2025 A+ GRADE
ANSWERS
03 ao + 02
9. What is a dobson unit? How is it used in relation to atmospheric
ozone levels?: One dobson unit is equivalent to 0.01 mm thick of
pure ozone at the density it posses if at ground level pressure
and temp. T He total amount of atmospheric ozone that lies over
a given point on earth is measured in terms of dobson units.
10. Overheat ozone concentrationis 250 DU what is the thickness
in mm?: -
2.5mm
1 1 . Describe the process by which chlorine becomes activated in the
Antartic ozone hole phenomena.: - Special polar winter weather
conditions in the polar atmosphere temporarily convert all the chlorine
that is chemically inactive form such as HCI and CION02 into the active
forms Cl and CIO. The conversion of inactive to active chlorine occurs at
the surface of particles formed on the solution of water, H2S04 and
HN03, the latter formed by OH and N02.
12. Explain thy full scale ozone holes have not yet been observed for
the Arctic.: Stratospheric temperature over the Arctic does not fall as
long for a long and air circulation to surrounding areas is not limited
13. Define what is meant by tropospheric sink.: natural removal
process such as dissolution in rain or oxidization by atmospheric gases
that occurs in the tropospheric 14. What are HCFC's?:
hydrochlorofluorocarbons
15. What state and sort of reaction provides a trososperic sink for
them?: gas state
16. Is their destructin in the troposphere 100% complete? : no
17. Why are HCFC's not considered suitable for long-term
replacements for CFC's?: Not considered long term
replacements because its long term ozone reducing potential
2/5
STUDY MATERIAL. 2024/2025 A+ GRADE
ANSWERS
1 . Which of the three gases constitute most of Earth's
atmosphere? : Nitrogen78%
Oxygen- 21 %
Aragon-I %
C020.04%
2. What range of altitudes constitutes the troposphere?
Stratosphere? : Troposphere- extends from ground level to
15km altitude and contains 85% of earths mass
Stratosphere- protion of atmosphere from 15-50km altitude
3. What atmospheric gas is primarily responsible for filtering
sunlight in the 120-220 nm range? Which, if any, absorbs most
of the Sun's rays in th e222-320 nm range? Which absorbs
primarily in the 320-400 nm range?: oxygen-120-220nm 03-
222-320nm
N02- 320-400nm
4. What is the game given to the finite packets of light absorbed
by matter? : UV-B
5. What is photochemically dissociated: atoms and molecules that
absorb light immediately undergo a change in the organization of
their electrons
6. Equation for ozone is formed in the stratosphere.: O + 02 -> 03
+ Heat
7. Two reaction that contribute to ozone destruction.: 03 + UV
photon (»<326m)
02 + O
03 + o 202
8. What two steps destroy ozone in the middle and upper
stratosphere?: Cl +
1/5
, CHEM 171. QUESTIONS AND ANSWERS.
STUDY MATERIAL. 2024/2025 A+ GRADE
ANSWERS
03 ao + 02
9. What is a dobson unit? How is it used in relation to atmospheric
ozone levels?: One dobson unit is equivalent to 0.01 mm thick of
pure ozone at the density it posses if at ground level pressure
and temp. T He total amount of atmospheric ozone that lies over
a given point on earth is measured in terms of dobson units.
10. Overheat ozone concentrationis 250 DU what is the thickness
in mm?: -
2.5mm
1 1 . Describe the process by which chlorine becomes activated in the
Antartic ozone hole phenomena.: - Special polar winter weather
conditions in the polar atmosphere temporarily convert all the chlorine
that is chemically inactive form such as HCI and CION02 into the active
forms Cl and CIO. The conversion of inactive to active chlorine occurs at
the surface of particles formed on the solution of water, H2S04 and
HN03, the latter formed by OH and N02.
12. Explain thy full scale ozone holes have not yet been observed for
the Arctic.: Stratospheric temperature over the Arctic does not fall as
long for a long and air circulation to surrounding areas is not limited
13. Define what is meant by tropospheric sink.: natural removal
process such as dissolution in rain or oxidization by atmospheric gases
that occurs in the tropospheric 14. What are HCFC's?:
hydrochlorofluorocarbons
15. What state and sort of reaction provides a trososperic sink for
them?: gas state
16. Is their destructin in the troposphere 100% complete? : no
17. Why are HCFC's not considered suitable for long-term
replacements for CFC's?: Not considered long term
replacements because its long term ozone reducing potential
2/5
