Correct Answer:
(B) Stratosphere
The earth’s atmosphere is divided into several layers and each layer plays an important role. The layer extending about 10-50 km is called the stratosphere. The ozone layer is mainly found in the lower portion of the stratosphere from approximately 15 to 30 kilometres above the Earth, though the thickness varies seasonally and geographically. The ozone layer protects the Earth from the sun UV rays. 10% of the ozone layer is found in the troposphere and 90% in the stratosphere.
Ques: 2
Ozone layer is above the earth's crust around –
Correct Answer:
(D)
20 km.
The Ozone layer is mainly found in stratosphere from approximately 15 to 30 km above the Earth's surface. Its density varies seasonally and geographically.
Ques: 3
The radiation that is absorbed by ozone present in the atmosphere is –
Correct Answer:
(C) Ultraviolet
Ozone (O3) is a molecule formed by three atoms of oxygen. While O2, which we normally refer to as oxygen, is essential for all aerobic forms of life. Ozone is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the Earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms and is known to cause skin cancer in human beings.
Ques: 4
“Ozone Layer Preservation Day” is celebrated on –
Correct Answer:
(A) 16 September
In 1994, the UN General Assembly declared 16 September as the International Day for the Preservation of the Ozone Layer, commemorating the date of the signing, of the Montreal Protocol on Substances that deplete the Ozone Layer in 1987.
Ques: 5
The ozone hole is caused by
Correct Answer:
(C) Chlorofluorocarbons
Ozone depletion occurs when chlorofluorocarbons (CFC) are released into the atmosphere. These gases, through several chemical reactions, cause the ozone molecules to break down, reducing ozone’s ultraviolet radiation absorbing capacity.
Ques: 6
Which one of the following is not responsible for the depletion of ozone layer:
Correct Answer:
(B) Methyl chloroform used as a solvent
The ozone layer in the atmosphere prevents harmful ultraviolet rays from reaching the Earth's surface. It thus safeguards life on Earth. Gases responsible for the depletion of the ozone layer are– CFC, Halon - 1211, 1301, Nitrous oxide and Trichloroethylene etc.
Ques: 7
Among the following greenhouse gases, which does not cause ozone depletion in the troposphere?
Correct Answer:
(B) Carbon monoxide
The greenhouses gases responsible for ozone depletion in the troposphere are- Water vapour, Carbon dioxide, Methane, Ozone, Nitrous oxide and Chlorofluorocarbons.
Ques: 8
Formation of the ozone hole is maximum over –
Correct Answer:
(C) Antarctica
The ozone hole is not technically a “hole” where no ozone is present but is a region of exceptionally depleted ozone in the stratosphere over Antarctica.
Ques: 9
Consider the following statements: Chlorofluorocarbons, known as ozone-depleting substances, are used
In the production of plastic foams.
In the production of tubeless tires.
In cleaning certain electronic components.
As pressurizing agents in aerosol cans.
Which of the statements given above is/are correct?
Correct Answer:
(C) 1, 3 and 4
Chlorofluorocarbons (CFCs) are nontoxic, non-flammable chemicals containing atoms of carbon, chlorine, and fluorine. They are used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants. Trichlorofluoromethane can dissolve grease and used to clean electronic equipment. It is a highly stable compound and can sustain in the atmosphere for 80 to 100 years. Hence option (C) is the correct answer.
Ques: 10
Which of the following substances is/are ozone depleting?
Select the correct answer from codes given below:
Chlorofluorocarbons
Halans
Carbon tetrachloride
Codes :
Correct Answer:
(D)
1, 2 and 3
Chlorofluorocarbons, Halans and Carbon tetrachloride, all are ozone-depleting substances. All these substances are banned after the Montreal Protocol.
Ques: 11
The formation of the ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole?
Correct Answer:
(B) Presence of prominent polar front and stratospheric clouds and inflow of chlorofluorocarbons
Nitric Acid in the Polar stratospheric clouds react with chlorofluorocarbon. This reaction produces chlorine which is responsible for photo-chemical destruction of the ozone layer. Since stratospheric clouds help chlorine compound to convert in chlorine particles depleting the ozone layer, their presence is also a factor responsible for the formation of the ozone hole.
Ques: 12
Which gas is filled in refrigerators?
Correct Answer:
(B) Mafron
The gases filled in the refrigerator are sold as Mafron. These gases are a commonly halonic hydrocarbon. Although, Ammonia is also used as a coolant in big plants, the correct answer to this question is option (b).