Ncert Solutions Chemistry Class 11th
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The gaseous envelope around the earth is known as the atmosphere. The lowest layer of this is extended up to 10 km from sea level, this layer is _________.
(i) Stratosphere
(ii) Troposphere
(iii) Mesosphere
(iv) Hydrosphere
The gaseous envelope around the earth is known as the atmosphere. The lowest layer of this is extended up to 10 km from sea level, this layer is _________.
(i) Stratosphere
(ii) Troposphere
(iii) Mesosphere
(iv) Hydrosphere
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (ii) Troposphere is correct since the lowest region of atmosphere in which the human beings along with other organisms live is called troposphere. It extends up to the height of approximately 10 km from sea level.
Upvote 
Which of the following statements about photochemical smog is wrong?
(i) It has a high concentration of oxidizing agents.
(ii) It has a low concentration of oxidizing agents.
(iii) It can be controlled by controlling the release of NO2 , hydrocarbons, ozone etc.
(iv) Plantation of some plants like Pinus helps in controlling photochemical smog.
Which of the following statements about photochemical smog is wrong?
(i) It has a high concentration of oxidizing agents.
(ii) It has a low concentration of oxidizing agents.
(iii) It can be controlled by controlling the release of NO2 , hydrocarbons, ozone etc.
(iv) Plantation of some plants like Pinus helps in controlling photochemical smog.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (ii) i.e., It has low concentration of oxidizing agents is the answer since the common components of photochemical smog are ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate (PAN). Photochemical smog causes
Upvote Sewage containing organic waste should not be disposed of in water bodies because it causes major water pollution. Fishes in such a polluted water die because of
(i) Large number of mosquitoes.
(ii) Increase in the amount of dissolved oxygen.
(iii) Decrease in the amount of dissolved oxygen in water.
(iv) Clogging of gills by mud.
Sewage containing organic waste should not be disposed of in water bodies because it causes major water pollution. Fishes in such a polluted water die because of
(i) Large number of mosquitoes.
(ii) Increase in the amount of dissolved oxygen.
(iii) Decrease in the amount of dissolved oxygen in water.
(iv) Clogging of gills by mud.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
i.e., Decrease in the amount of dissolved oxygen in water is the answer since organic waste is oxidized by microorganisms in the presence of dissolved oxygen. Hence, oxygen decreases in water as a result it is harmful for
Upvote Which of the following statements is wrong?
(i) Ozone is not responsible for the greenhouse effect.
(ii) Ozone can oxidize Sulphur dioxide present in the atmosphere to Sulphur trioxide.
(iii) Ozone hole is thinning of the ozone layer present in the stratosphere.
(iv) Ozone is produced in the upper stratosphere by the action of UV rays on oxygen.
Which of the following statements is wrong?
(i) Ozone is not responsible for the greenhouse effect.
(ii) Ozone can oxidize Sulphur dioxide present in the atmosphere to Sulphur trioxide.
(iii) Ozone hole is thinning of the ozone layer present in the stratosphere.
(iv) Ozone is produced in the upper stratosphere by the action of UV rays on oxygen.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i) i.e., Ozone is not responsible for greenhouse effect is the answer since O3 is responsible for the greenhouse effect, its contribution is about 8% to 10%. About 75% of the solar energy reaching the earth is absorbed
Upvote Which of the following statements is not true about classical smog?
(i) Its main components are produced by the action of sunlight on emissions of automobiles and factories.
(ii) Produced in cold and humid climates.
(iii) It contains compounds of reducing nature.
(iv) It contains smoke, fog, and Sulphur dioxide.
Which of the following statements is not true about classical smog?
(i) Its main components are produced by the action of sunlight on emissions of automobiles and factories.
(ii) Produced in cold and humid climates.
(iii) It contains compounds of reducing nature.
(iv) It contains smoke, fog, and Sulphur dioxide.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i)
i.e., Its main components are produced by the action of sunlight on emissions of automobiles and factories is the answer since classical smog is a mixture of smoke, fog and sulphur dioxide and occurs in cold humid climates.
Upvote Photochemical smog occurs in warm, dry, and sunny climate. One of the following is not amongst the components of photochemical smog, identify it.
(i) NO2
(ii) O3
(iii) SO2
(iv) Unsaturated hydrocarbon
Photochemical smog occurs in warm, dry, and sunny climate. One of the following is not amongst the components of photochemical smog, identify it.
(i) NO2
(ii) O3
(iii) SO2
(iv) Unsaturated hydrocarbon
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (iii)
SO2 is correct since photochemical fog is formed in the presence of sunlight in summers when NO and hydrocarbons are present in large amounts in the atmosphere. SO2 is not responsible for photochemical fog.
Upvote Which of the following gases is not a greenhouse gas?
(i) CO
(ii) O3
(iii) CH4
(iv) H2O vapour
Which of the following gases is not a greenhouse gas?
(i) CO
(ii) O3
(iii) CH4
(iv) H2O vapour
This is a Multiple Choice Questions as classified in NCERT Exemplar
Option (i)
CO is correct since it does not absorb sunlight near the earth's surface and hence it is not radiated back to the earth. Greenhouse gases have this kind of property.
Upvote Assertion (A): If BOD level of water in a reservoir is less than 5 ppm it is highly polluted.
Reason (R): High biological oxygen demand means low activity of bacteria in water.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct. (iv) A is not correct but R is correct.
Assertion (A): If BOD level of water in a reservoir is less than 5 ppm it is highly polluted.
Reason (R): High biological oxygen demand means low activity of bacteria in water.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct. (iv) A is not correct but R is correct.
This is a Assertion Type Questions as classified in NCERT Exemplar
Option (iii)
i.e., Both A and R are not correct since the amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water, is called BOD i.e., Biochemical Oxygen
Upvote Assertion (A): Excessive use of chlorinated synthetic pesticides causes soil and water pollution.
Reason (R): Such pesticides are non-biodegradable.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct.
(iv) A is not correct but R is correct.
Assertion (A): Excessive use of chlorinated synthetic pesticides causes soil and water pollution.
Reason (R): Such pesticides are non-biodegradable.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct.
(iv) A is not correct but R is correct.
This is a Assertion Type Questions as classified in NCERT Exemplar
Option (i)
i.e., Both A and R are correct, and R is the correct explanation of A is the answer since pesticides are the synthetic toxic chemicals with ecological repercussions and their repeated use gives rise to pests that
Upvote Assertion (A) :Ozone is destroyed by solar radiation in the upper stratosphere.
Reason (R) : Thinning of the ozone layer allows excessive UV radiations to reach the surface of earth.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct.
(iv) A is not correct but R is correct.
Assertion (A) :Ozone is destroyed by solar radiation in the upper stratosphere.
Reason (R) : Thinning of the ozone layer allows excessive UV radiations to reach the surface of earth.
(i) Both A and R are correct, and R is the correct explanation of A.
(ii) Both A and R are correct, but R is not the correct explanation of A.
(iii) Both A and R are not correct.
(iv) A is not correct but R is correct.
This is a Assertion Type Questions as classified in NCERT Exemplar
Option (iv)
i.e., A is not correct, but R is correct since ozone in the stratosphere is a product of ultraviolet radiations falling on oxygen molecules. The main cause of ozone layer depletion is the release of CFCs i.e., freons.
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