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

(1) Which of the following gases is not a green house gas?
[A] CO
[B] O3
[C] CH4
[D] H2O vapour
Answer: CO
(2) Photochemical smog occurs in warm, dry and sunny climate. One of the following is not amongst the components of photochemical smog, identify it.
[A] NO2
[B] O3
[C] SO2
[D] Unsaturated hydrocarbon
Answer: SO2

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(3) 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.
(4) Biochemical Oxygen Demand, (BOD) is a measure of organic material present in water. BOD value less than 5 ppm indicates a water sample to be __________.
[A] rich in dissolved oxygen.
[B] poor in dissolved oxygen.
[C] highly polluted.
[D] not suitable for aquatic life.
Answer: rich in dissolved oxygen.
(5) Which of the following statements is wrong?
[A] Ozone is not responsible for green house effect.
[B] Ozone can oxidise 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 green house effect.
(6) 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.
(7) Which of the following statements about photochemical smog is wrong?
[A] It has high concentration of oxidising agents.
[B] It has low concentration of oxidising agent.
[C] It can be controlled by controlling the release of NO2, hydrocarbons, ozone etc.
[D] Plantation of some plants like pinus helps in controlling photochemical smog
Answer: It has low concentration of oxidising agent.
(8) The gaseous envelope around the earth is known as atmosphere. The lowest layer of this is extended upto 10 km from sea level, this layer is _________.
[A] Stratosphere
[B] Troposphere
[C] Mesosphere
[D] Hydrosphere
Answer: Troposphere
(9) Dinitrogen and dioxygen are main constituents of air but these do not react with each other to form oxides of nitrogen because _________.
[A] the reaction is endothermic and requires very high temperature.
[B] the reaction can be initiated only in presence of a catalyst.
[C] oxides of nitrogen are unstable.
[D] N2 and O2 are unreactive.
Answer: the reaction is endothermic and requires very high temperature.
(10) The pollutants which come directly in the air from sources are called primary pollutants. Primary pollutants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants?
[A] CO
[B] Hydrocarbon
[C] Peroxyacetyl nitrate
[D] NO
Answer: Peroxyacetyl nitrate
(11) Which of the following statements is correct?
[A] Ozone hole is a hole formed in stratosphere from which ozone oozes out.
[B] Ozone hole is a hole formed in the troposphere from which ozone oozes out.
[C] Ozone hole is thinning of ozone layer of stratosphere at some places.
[D] Ozone hole means vanishing of ozone layer around the earth completely.
Answer: Ozone hole is thinning of ozone layer of stratosphere at some places.
(12) Which of the following practices will not come under green chemistry?
[A] If possible, making use of soap made of vegetable oils instead of using synthetic detergents.
[B] Using H2O2 for bleaching purpose instead of using chlorine based bleaching agents.
[C] Using bicycle for travelling small distances instead of using petrol/ diesel based vehicles.
[D] Using plastic cans for neatly storing substances.
Answer: Using plastic cans for neatly storing substances.
(13) Which of the following conditions shows the polluted environment.
[A] pH of rain water is 5.6.
[B] amount of carbondioxide in the atmosphere is 0.03%.
[C] biochemical oxygen demand 10 ppm.
[D] eutrophication.
Answer: C, D
(14) Phosphate containing fertilisers 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
(15) The acids present in acid rain are _________.
[A] Peroxyacetylnitrate
[B] H2CO3
[C] HNO3
[D] H2SO4
Answer: B, C, D
(16) The consequences of global warming may be _________.
[A] increase in average temperature of the earth
[B] melting of Himalayan Glaciers.
[C] increased biochemical oxygen demand.
[D] eutrophication
Answer: A, B
(17) Assertion (A): Green house effect was observed in houses used to grow plants and these are made of green glass.

Reason (R) : Green house name has been given because glass houses are made of green glass.

[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.
(18) Assertion (A) : The pH of acid rain is less than 5.6.

Reason (R) : Carbon dioxide present in the atmosphere dissolves in rain water and forms carbonic acid.

[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 but R is not the correct explanation of A.
(19) Assertion (A) : Photochemical smog is oxidising in nature.

Reason (R) : Photochemical smog contains NO2 and O3, which are formed during the sequence of reactions.

[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.
(20) Assertion (A) : Carbon dioxide is one of the important greenhouse gases.

Reason (R) : It is largely produced by respiratory function of animals and plants.

[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 but R is not the correct explanation of A.

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