Q1: Statement 1: Ozone is a form of oxygen with three atoms.
Statement 2: Ozone in the troposphere is considered beneficial as it contributes to reducing air pollution.
(a) Both Statement 1 and Statement 2 are true.
(b) Statement 1 is true, but Statement 2 is false.
(c) Statement 1 is false, but Statement 2 is true.
(d) Both Statement 1 and Statement 2 are false.
Ans: (b)
Ozone is indeed a form of oxygen with three atoms (Statement 1 is true), but in the troposphere, it is considered "bad" because it contributes to air pollution and smog (Statement 2 is false).
Q2: Statement 1: The Dobson unit is a measure of ozone concentration.
Statement 2: One Dobson unit is equivalent to 2.69 x 1020 molecules per square meter at Standard Temperature and Pressure.
(a) Both statements are true.
(b) Both statements are false.
(c) Statement 1 is true, and Statement 2 is false.
(d) Statement 1 is false, and Statement 2 is true.
Ans: (a)
The Dobson unit measures the total amount of ozone in a column of air stretching from the surface of the Earth to the edge of space. One Dobson Unit represents a layer of ozone that would be 10 micrometers thick under standard temperature and pressure conditions.
Q3: The ozone layer depletion is mainly caused by Nitrogen Oxides (NOx).
(a) True
(b) False
Ans: (b)
The primary cause of ozone layer depletion is chlorofluorocarbons (CFCs), not Nitrogen Oxides (NOx).
Q4: Assertion (A): CFCs were widely used as refrigerants and in aerosol propellants.
Reason (R): CFCs are chemically stable and non-flammable.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
CFCs were indeed widely used in various applications because of their properties such as chemical stability and non-flammability.
Q5: Arrange the following events in the order of their occurrence during Antarctic ozone depletion:
1. Formation of Polar Stratospheric Clouds
2. Breakdown of the polar vortex
3. Sunlight returns, catalytic destruction of ozone
(a) 1-3-2
(b) 2-1-3
(c) 3-2-1
(d) 2-3-1
Ans: (a)
The sequence starts with the formation of Polar Stratospheric Clouds, followed by catalytic destruction of ozone upon the return of sunlight, and finally, the breakdown of the polar vortex.
Q6: Which of the following pairs is incorrectly matched?
(a) Chlorine Atoms - Breakdown of CFCs
(b) Methyl Bromide - Used in agriculture as a pesticide
(c) Sulphuric Acid Particles - Promote ozone formation
(d) HCFCs - Interim substitutes for CFCs
Ans: (c)
Sulphuric Acid Particles do not promote ozone formation. Instead, they contribute to ozone depletion by freeing chlorine and converting reactive nitrogen into inert forms.
Q7: The Ozone Depleting Substances (Regulation and Control) Rules, 2000, allow the use of HCFCs until January 1, 2040.
(a) True
(b) False
Ans: (a)
The rules indeed permit the use of HCFCs, interim substitutes for CFCs, until January 1, 2040.
Q8: Statement 1: CFCs have a high ozone layer depletion potential.
Statement 2: HCFC-141b was phased out in India by January 1, 2020.
(a) Both Statement 1 and Statement 2 are true.
(b) Statement 1 is true, but Statement 2 is false.
(c) Statement 1 is false, but Statement 2 is true.
(d) Both Statement 1 and Statement 2 are false.
Ans: (a)
CFCs do have a high ozone layer depletion potential, and HCFC-141b was successfully phased out in India by the specified date.
Q9: Ozone absorbs sunlight, leading to an increase in temperature with altitude in the stratosphere. This absorption is crucial for _______.
(a) Tropospheric cooling
(b) Stratospheric warming
(c) Mesospheric stability
(d) Thermospheric variations
Ans: (b)
Ozone's absorption of sunlight causes a temperature increase in the stratosphere, leading to stratospheric warming.
Q10: Assertion (A): Ozone depletion has led to an increased incidence of skin cancer and eye diseases.
Reason (R): Ozone layer depletion results in increased penetration of harmful UV-B radiation to the Earth's surface.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
The depletion of the ozone layer has indeed led to increased cases of skin cancer and eye diseases due to the increased penetration of harmful UV-B radiation.
Q11: Ozone layer depletion is more severe over the Arctic than over the Antarctic.
(a) True
(b) False
Ans: (b)
Ozone layer depletion is more severe over the Antarctic, where the phenomenon of the 'ozone hole' was first observed.
Q12: Assertion (A): The Antarctic vortex confines ozone depletion in the Antarctic region.
Reason (R): The vortex stabilizes due to low temperatures and the formation of Polar Stratospheric Clouds (PSCs).
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
The Antarctic vortex, a rapidly circulating air mass, indeed confines ozone depletion to the Antarctic region. Its stability is influenced by low temperatures and the formation of Polar Stratospheric Clouds.
Q13: Which of the following statements about the ozone layer is incorrect?
(a) The ozone layer absorbs harmful UV rays from the sun.
(b) Ozone in the stratosphere is considered harmful.
(c) Ozone depletion can lead to increased cases of skin cancer.
(d) The Dobson unit is a measure of ozone layer thickness.
Ans: (b)
Ozone in the stratosphere is beneficial as it absorbs harmful UV rays. It is only harmful when present in the troposphere.
Q14: Assertion (A): The Antarctic vortex confines ozone depletion to the Antarctic region.
Reason (R): The vortex is a ring of rapidly circulating air that isolates the Antarctic stratosphere.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
The Antarctic vortex does indeed confine ozone depletion to the Antarctic region, and it is a ring of rapidly circulating air that isolates the region's stratosphere.
Q15: Sequence the following events in the process of Antarctic Ozone Depletion:
1. Sunlight returns, catalytic destruction of ozone occurs.
2. Antarctic winter begins, vortex develops.
3. Polar vortex breaks down, ozone starts replenishing.
4. PSCs form, allowing chlorine and bromine reactions.
(a) 2, 4, 1, 3
(b) 4, 2, 3, 1
(c) 2, 1, 4, 3
(d) 1, 3, 2, 4
Ans: (a)
The sequence starts with the development of the Antarctic vortex during winter, followed by PSC formation, catalytic destruction of ozone upon the return of sunlight, and finally the breakdown of the vortex and replenishment of ozone.
Q16: Methyl bromide is used primarily as a fire extinguishing agent.
(a) True
(b) False
Ans: (b) False
Methyl bromide is primarily used as a pesticide, not as a fire extinguishing agent.
Q17: Arrange the following steps in the process of ozone depletion:
1. Release of chlorine atoms from CFCs
2. Formation of chlorine monoxide
3. Destruction of ozone molecules
(a) 1-2-3
(b) 2-1-3
(c) 3-2-1
(d) 1-3-2
Ans: (a)
First, chlorine atoms are released from CFCs; then they form chlorine monoxide, which subsequently leads to the destruction of ozone molecules.
Q18: The primary reason for the seasonal ozone hole over the Antarctic is the presence of _______.
(a) Polar Stratospheric Clouds
(b) Increased industrial pollution
(c) Higher solar radiation
(d) Elevated CO2 levels
Ans: (a)
The formation of Polar Stratospheric Clouds is a key factor in the seasonal ozone hole over the Antarctic.
Q19: Statement 1: The Dobson unit measures the concentration of ozone in parts per million.
Statement 2: One Dobson unit represents the thickness of the ozone layer in milli-centimeters.
(a) Both Statement 1 and Statement 2 are true.
(b) Statement 1 is true, but Statement 2 is false.
(c) Statement 1 is false, but Statement 2 is true.
(d) Both Statement 1 and Statement 2 are false.
Ans: (c)
The Dobson unit actually represents the thickness of the ozone layer in milli-centimeters, not its concentration in parts per million.
Q20: Assertion (A): UV-B radiation can adversely affect human health.
Reason (R): UV-B radiation increases due to a decrease in the quantity of total-column ozone.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true
Ans: (a)
Increased levels of UV-B radiation, a result of decreased total-column ozone, can indeed have adverse effects on human health.
