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NCERT Solutions for class 11 Chemistry | Chapter 14 : Environmental Chemistry

Questions
1 Assertion (A) : Ozone is destroyed by solar radiation in upper stratosphere.

Reason (R) : Thinning of the ozone layer allows excessive UV radiations to reach the surface of earth.

A Both A and R are correct and R is the correct explanation of A.
B Both A and R are correct but R is not the correct explanation of A.
C Both A and R are not correct.
D A is not correct but R is correct.

Answer:A is not correct but R is correct.
2 Assertion (A) : Excessive use of chlorinated synthetic pesticides causes soil and water pollution.

Reason (R) : Such pesticides are non-biodegradable.

A Both A and R are correct and R is the correct explanation of A.
B Both A and R are correct but R is not the correct explanation of A.
C Both A and R are not correct.
D A is not correct but R is correct.

Answer:Both A and R are correct and R is the correct explanation of A.
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3 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.

A Both A and R are correct and R is the correct explanation of A.
B Both A and R are correct but R is not the correct explanation of A.
C Both A and R are not correct.
D A is not correct but R is correct.

Answer:Both A and R are not correct.
4 In the air, N2 and O2 occur naturally but they do not react to form oxides of nitrogen because
A oxides of nitrogen are unstable
B catalyst is required for the reaction
C the reaction is endothermic
D N2 and O2 do not react with each other

Answer:the reaction is endothermic
5 The compound essential for the process of photosynthesis has this element
A Ca
B Ba
C Fe
D Mg

Answer:Mg
6 Which of the oxide of nitrogen is not a common pollutant?
A N2O5
B N2O
C NO
D NO2

Answer:N2O5
7 The coldest region of the atmosphere
A Troposphere
B Thermosphere
C Stratosphere
D Mesosphere

Answer:Mesosphere
8 Alum’s capacity to purify water is due to
A softens hard water
B pathogenic bacteria get destroyed
C impurities’ coagulation
D it improves taste

Answer:impurities’ coagulation
9 The reaction responsible for the radiant energy of the Sun is
A nuclear fission
B nuclear fusion
C chemical reaction
D combustion

Answer:nuclear fusion
10 Find the secondary pollutant among these
A PAN
B N2O
C SO2
D CO2

Answer:PAN
11 Find the incorrect statement
A BOD value of clean water is less than 5 ppm
B Drinking water pH should be between 5.5-9.5
C carbon, sulphur and nitrogen oxides are the most widespread air pollutants
D dissolved oxygen concentration below 5 ppm is ideal for the growth of fish

Answer:dissolved oxygen concentration below 5 ppm is ideal for the growth of fish
12 Depletion of the ozone layer is caused due to
A Ferrocene
B Fullerenes
C Freons
D Polyhalogens

Answer:Freons
13 Photochemical smog normally does not contain
A Chlorofluorocarbons
B Peroxyacetyl nitrate
C Ozone
D Acrolein

Answer:Chlorofluorocarbons
14 The gaseous envelope around the earth is known as atmosphere. The lowest layer of this is extended up to 10 km from sea level. This layer is .
A Stratosphere
B Troposphere
C Mesosphere
D Hydrosphere

Answer:Troposphere
15 Which of the following statements about photochemical smog is wrong?
A It has high concentration of oxidizing agents.
B It has low concentration of oxidizing agent.
C It can be controlled by controlling the release of N02, hydrocarbons, ozone etc.
D Plantation of some plants like pinus helps in controlling photochemical

Answer:It has low concentration of oxidizing agent.
16 Sewage containing organic waste should not be disposed in water bodies because it causes major water pollution. Fishes in such a polluted water die because of
A large number of mosquitoes.
B increase in the amount of dissolved oxygen.
C decrease in the amount of dissolved oxygen in water.
D clogging of gills by mud.

Answer:decrease in the amount of dissolved oxygen in water.
17 Which of the following statements is wrong? . ‘
A Ozone is not responsible for greenhouse effect.
B Ozone can oxidize sulphur dioxide present in the atmosphere to sulphur trioxide.
C Ozone hole is thinning of ozone layer present in stratosphere.
D Ozone is produced in upper stratosphere by the action of UV rays on oxygen .

Answer:Ozone is not responsible for greenhouse effect.
18 Which of the following statements is not true about classical smog?
A Its main components are produced by the action of sunlight on emissions of automobiles and factories.
B Produced in cold and humid climate.
C It contains compounds of reducing nature.
D It contains smoke, fog and sulphur dioxide.

Answer:Its main components are produced by the action of sunlight on emissions of automobiles and factories.
19 Photochemical smog occurs in warm, dry and sunny climate. One of the following is not amongst the components of photochemical smog, identify it.
A N02
B 03
C S02
D Unsaturated hydrocarbon

Answer:S02
20 Phosphate containing fertilizers cause water pollution. Addition of such compounds in water bodies causes
A enhanced growth of algae
B decrease in amount of dissolved oxygen in water
C deposition of calcium phosphate
D increase in fish population

Answer:A, B

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