Ozone and its depletion - class-XII
Description: ozone and its depletion | |
Number of Questions: 24 | |
Created by: Sanjiv Memon | |
Tags: biology physical resources chemistry environmental issues natural resources - air, water and land pollution - a rising environmental problem environment commercial applications ecology and environment depletion of resources p-block elements biogeochemical cycles zoology not for breathing not for drinking global environmental change the p-block elements p- block elements-ii our environment |
Ozone layer of upper atmosphere is being destroyed by
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Chlorofluorocarbons
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$ { SO } _{ 2 } $
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Smog
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None of the above
Ozone hole means
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Hole in the stratosphere
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Same concentration of ozone
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Decrease in the concentration of ozone
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Increase in the concentration of ozone
Ozone occurs in the concentration of up to 1 ppm in the stratosphere as compared to 0.5 ppm in the troposphere. Ozone is formed in the stratosphere from oxygen due to solar radiations. Maximum ozone concentration is found at a distance of 23 to 25 km above the equator and 11 to 16 km over poles. It is called as ozone layer or ozonosphere.
Formation of ozone hole is maximum over
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India
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Antarctica
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Europe
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Africa
The thickness of ozone over the poles changes with the seasons being lowest in polar spring and maximum in polar autumn. Ozone hole refers to the depletion in the concentration of ozone over a restricted area as spring time decline over Antarctica. Spring time depletion of ozone is due to the action of sunlight over pollutants, which release chemicals like chlorine, that destroy ozone.
Ozone hole means
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Hole in the stratosphere
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Same concentration of ozone
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Decrease in concentration of ozone
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Increase in the concentration of ozone
In atmosphere , Ozone hole refers to
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A hole in ozone layer
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Decrease in ozone layer thickness in troposphere
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Decrease in thickness of ozone layer in stratosphere
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Increase in the thickness of ozone layer in troposphere
The region of stratosphere, at an altitude of 16-50km over equator and at a slightly lower altitude elsewhere having a thick sheet of ozone is known as ozonosphere. Decline in the thickness of ozone layer over a restricted area is called ozone hole. It was first discovered over Antarctica in 1985 by Dr. Joe C. Farman and his colleagues in the British Antarctica surveys. Chlorofluorocarbons are mainly responsible for ozone depletion in the stratosphere. CFC's are used as coolants in refrigerators and air conditioners, as propellants, cleaning solvents. Once released into the atmosphere, CFC'S reach the stratosphere and produce active chlorine in the presence of UV radiations. These radicals through chain reaction destroy ozone by converting it into oxygen.
The pollutant that causes hole in the ozone layer is
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$SF _{6}$
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nitrousoxide
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$CFC _{s}$
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$PFC _{s}$
'Ozone-hole' means
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A large sized hole in the ozone layer
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Thinning of the ozone layer
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Small holes scattered in the ozone layer
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Thickening of ozone in the ozone layer
Ozone layer is a region of concentration of ozone molecule. $O _3 (O _2+
O)$ in the earth's atmosphere. The layer lies in the stratosphere at an
altitude of 18-50 kms. The ozone layer naturally Shields earth's life
from the harmful effect of the Sun's ultraviolet radiations. A severe
depletion of ozone (ozone hole) in a region of the ozone layer was found
particularly over Antarctica. The depletion is caused by
chlorofluorocarbons and by other compounds like $CCI _4, CF _4$ etc. So, the correct answer is 'Thinning of the ozone layer'.
In which part of atmosphere, ozone layer is present?
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Stratosphere
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Troposphere
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Mesosphere
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Thermosphere
The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres above Earth, which shields the earth from the sun's harmful ultraviolet radiations. Ozone gas is present in 10 ppm in this ozone layer.
Ozone hole was first detected over
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Antarctica
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Arctic circle
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Equator
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Polar region
Ozone hole means
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A large sized in the stratosphere layer
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Thinning of the ozone layer at the poles
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Small holes scattered in the ozone layer
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Thickening of the ozone layer at the poles
We know that surrounding the troposphere of earth, there is a layer of the stratosphere. It is made up of ozone molecules that are formed by the effect of UV rays in these areas. Due to excessive chlorofluorocarbon compounds, and emission of carbon dioxide, it is getting depleted. At the poles, it is constantly getting thinner and thinner. This is called the ozone hole.
Depletion of ozone layer is noticed on
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America
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Asia
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Australia
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All over the earth
Depletion of ozone layer is noticed all over the earth.
Ozone is destroyed by collisions with other atoms and molecules.
Ozone loss was first detected in the stratosphere over the
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Arctic
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Antarctic
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Africa
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Australia
- An ozone hole is depletion of the ozone layer which is present in the stratosphere region around 26-30kms above the Earth surface. It was first detected in the stratosphere over Antarctica.
- It is caused by chlorofluorocarbons (CFCs) found in air conditioners, aerosol spray cans, refrigerants, etc. CFCs can not be removed in the troposphere and moves in the stratosphere layer where it reacts with ozone, thereby releasing of free chlorine atoms and causes the ozone layer to deplete.
Ozone hole refers to
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Hole is ozone layers
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Reduction in thickness of ozone layer in stratosphere
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Reduction of thickness of ozone in troposphere
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Increase concentration of ozone
When the oxygen-depleting substances like CFCs, HFCs, methyl bromide etc. find their way to the stratosphere, the UV rays spilt them to release the reactive species of chlorine and bromine. These reactive species react with the ozone to release the oxygen, thereby causing the depletion of ozone. The ozone hole is the place where the thickness of the ozone layer is very thin and the concentration is less than 220 DU. It is seen over Antarctica due to the process of polar vortex and formation of polar stratospheric clouds.
According to the recent reports, the country contributed maximum to hole formation in ozone layer is
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U.S.A.
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Russia
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Germany
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Japan
The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS). the United States National Academy of Sciences concluded that credible scientific evidence supported the ozone depletion hypothesis[59] a few countries, including the United States, Canada, Sweden, Denmark, and Norway, moved to eliminate the use of CFCs in aerosol spray cans. The United States banned the use of CFCs in aerosol cans in 1978.[60] The European Community rejected proposals to ban CFCs in aerosol sprays.
Multiple Choice Questions
Ozone layer occurs in
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troposphere
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stratosphere
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mesosphere
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exosphere
Ozone or O$ _3$ is a triatomic gas that forms a layer in the upper part of atmosphere called the Stratosphere. It acts as a shield against harmful radiations of the sun.
"Ozone Hole" is a _______________
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Hole in the atmosphere
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Destruction of ozone layer
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Hole in the hydrosphere
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Hole in the troposphere
The horizontal extent of the ozone hole can sometimes exceed the size of the Antarctic continent.
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True
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False
Antarctic ozone hole was caused by
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CFCs
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PAN
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$CO _{2}$
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CO
Antarctic ozone layer is known as
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Ozone hole
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Stratosphere
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Mesosphere
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All of above
Troposphereic' ozone harmful effects on humans, included:
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Chest pain
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Throat irritation
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Vomiting
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Both a and b
Result of ozone hole is
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UV radiation reaching earth
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Green house effect
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Acid rain
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Global warming
Ozone layer is present in the stratosphere which absorbs the harmful ultraviolet radiation Ultraviolet rays cause heritable mutational changes. They have the capability to destroy plants and animals and can cause skin cancer, cataracts to human beings. Existence of life on earth is possible only because of the presence of ozone layer around the earth. The main cause of the ozone hole was found to be gases that contained chlorofluorocarbons (CFCs), halons and freons. Found commonly in aerosol cans and released by many electronic appliances, these decrease the level of ozone in the stratosphere. All of these gases contain chlorine, which is a major cause behind the thinning of the ozone layer. The presence of chlorine within CFCs break down the ozone gases in ozone layer which increases the chances of ozone depletion. CFCs have accounted for about 80% of ozone depletion.
Ozone hole over Antarctica appears during
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Late August- Early October
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March- April
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October- November
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January- February
Polar spring, also known as the Antarctic Spring is the period from late August to early October and the strong westerlies circulate around the Antarctic continent creating a polar vortex. The polar vortex results in the formation of the polar stratospheric clouds which trap most of the gases including the ozone-depleting factors like CFCs, methyl bromide etc.
Ozone hole over Antarctica was first detected by
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Molina and Rowland
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Farman et al
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Augus
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Molina and Molina
The discovery of the ozone hole over Antarctica was done by British Antarctic Survey Scientist Farman, Gardiner and Shanklin and reported in the Nature journal in May 1985. The ozone hole is defined as the area in the atmosphere where the value of the ozone is less than 220 DU. Paul Crutzen, Mario Molina and Sherwood Rowland gave the observation of CFCs in degradation of the ozone.
Ozone hole is widest over
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Equator
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North pole
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North temperate area
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Antarctica
The ozone layer in the stratosphere is created by the interaction of the UV radiation from the sun and the oxygen. It is capable of absorbing the most damaging type of UV radiation called the UV-B. The ozone hole refers to the depletion of the ozone by the pollutants like CFCs, HCFCs and HFCs. The pollutants split up due to UV radiation and the nascent chlorine reacts with the ozone molecules to form the oxygen. Over Antarctica, the ozone is highly depleted and so the widest ozone hole is seen there. This is because of the presence of the stratospheric cloud in abundance.