JEE Chemistry Environmental Chemistry MCQs Set 18

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Chapter-wise Objective Questions: Environmental Chemistry

Navigate directly to the 50 objective questions for Environmental Chemistry using the digital viewer below. Each practice set includes verified answer keys, allowing students to instantly cross-check their work and identify areas requiring further revision.

Multiple Choice Questions

Question 1: Which of the following statements is false?
(a) London smog is oxidising in nature
(b) photochemical smog causes irritation in eyes
(c) London smog is a mixture of smoke and fog
(d) photochemical smog results in the formation of PAN
Show Answer & Explanation

Answer: (a) London smog is oxidising in nature

Explanation:
1. Classical (London) smog contains smoke, fog and \( \ce{SO2} \) and is reducing in nature.
2. Photochemical (Los Angeles) smog is oxidising, irritates the eyes and contains PAN.

Teacher's Note:
1. Classical smog is reducing, photochemical smog is oxidising.

Question 2: Identify the pollutant gases largely responsible for the discoloured and lustreless nature of the marble of the Taj Mahal:
(a) \( \ce{O3} \) and \( \ce{CO2} \)
(b) \( \ce{CO2} \) and \( \ce{NO2} \)
(c) \( \ce{SO2} \) and \( \ce{NO2} \)
(d) \( \ce{SO2} \) and \( \ce{O3} \)
Show Answer & Explanation

Answer: (c) \( \ce{SO2} \) and \( \ce{NO2} \)

Explanation:
1. \( \ce{SO2} \) and \( \ce{NO2} \) form sulphuric and nitric acids in the presence of moisture.
2. These acids attack the calcium carbonate of marble (acid rain), making it dull and lustreless.

Teacher's Note:
1. Acid rain corrodes marble.

Question 3: The false statement among the following is:
(a) the average residence time of NO is one month
(b) limestone acts as a sink for \( \ce{SOx} \)
(c) \( \ce{SOx} \) can be removed from flue gases by passing through a solution of citrate ions
(d) ammonia acts as a sink for \( \ce{NOx} \)
Show Answer & Explanation

Answer: (a) the average residence time of NO is one month

Explanation:
1. The residence time of NO in the atmosphere is only a few days, not a month.
2. The other three statements describe real sinks and removal methods.

Teacher's Note:
1. NO is quickly oxidised to NO2.

Question 4: Phosphate fertilisers when added to water lead to:
(a) increased growth of decomposers
(b) reduced algal growth
(c) increased dissolved oxygen
(d) nutrient enrichment (eutrophication)
Show Answer & Explanation

Answer: (d) nutrient enrichment (eutrophication)

Explanation:
1. Phosphates act as nutrients and cause rapid growth of algae (algal bloom).
2. When the algae die, decomposition removes dissolved oxygen, a process called eutrophication.

Teacher's Note:
1. Nutrient enrichment leads to oxygen depletion.

Question 5: Phosphate pollution is caused by:
(a) sewage and agricultural fertilisers
(b) weathering of phosphate rocks only
(c) agricultural fertilisers only
(d) phosphate rocks and sewage
Show Answer & Explanation

Answer: (a) sewage and agricultural fertilisers

Explanation:
1. Phosphates enter water mainly from domestic sewage (detergents) and run-off of agricultural fertilisers.

Teacher's Note:
1. Detergents and fertilisers are the main sources.

Question 6: Which causes death of fishes in water bodies polluted by sewage?
(a) foul smell
(b) pathogens
(c) clogging of gills by silt
(d) decrease in dissolved oxygen
Show Answer & Explanation

Answer: (d) decrease in dissolved oxygen

Explanation:
1. Decomposition of organic matter in sewage uses up dissolved oxygen.
2. Fish die when the dissolved oxygen falls too low.

Teacher's Note:
1. BOD rises and DO falls.

Question 7: A water sample is reported to be highly polluted if the BOD (Biological Oxygen Demand) value of the sample becomes:
(a) more than 17 ppm
(b) equal to 10 ppm
(c) equal to 5 ppm
(d) less than 5 ppm
Show Answer & Explanation

Answer: (a) more than 17 ppm

Explanation:
1. Clean water has a BOD below 5 ppm, and a BOD above about 17 ppm indicates highly polluted water.

Teacher's Note:
1. Higher BOD means more organic pollution.

Question 8: The region that is greatly affected by air pollution is:
(a) thermosphere
(b) stratosphere
(c) troposphere
(d) mesosphere
Show Answer & Explanation

Answer: (c) troposphere

Explanation:
1. The troposphere is the lowest layer of the atmosphere, where we live and where pollutants are released and accumulate.

Teacher's Note:
1. Pollutants are emitted at ground level.

Question 9: Which of the following is the most abundant hydrocarbon pollutant?
(a) butane
(b) ethane
(c) methane
(d) propane
Show Answer & Explanation

Answer: (c) methane

Explanation:
1. Methane is produced from natural sources such as marshes and from cattle and landfills, and it is the most abundant hydrocarbon pollutant.

Teacher's Note:
1. Methane is also a greenhouse gas.

Question 10: Synthesis of ethanal commercially from which of the following reagents is part of green chemistry?
(a) \( \ce{CH3CH2OH} \)
(b) \( \ce{CH2=CH2} \)
(c) \( \ce{HC#CH} \)
(d) all of these
Show Answer & Explanation

Answer: (b) \( \ce{CH2=CH2} \)

Explanation:
1. Ethene is oxidised directly to ethanal by oxygen in water with a Pd(II)/Cu(II) catalyst in one step (Wacker process), giving a high yield and little waste.

Teacher's Note:
1. Wacker process: ethene to ethanal.
2. Fewer steps and less waste.

Question 11: Addition of phosphate fertilisers to water bodies causes:
(a) increase in amount of dissolved oxygen in water
(b) deposition of calcium phosphate
(c) increase in fish population
(d) enhanced growth of algae
Show Answer & Explanation

Answer: (d) enhanced growth of algae

Explanation:
1. Phosphates are nutrients for algae, which grow rapidly in an algal bloom.
2. This later reduces the dissolved oxygen of the water.

Teacher's Note:
1. Algal bloom follows nutrient input.

Question 12: Greenhouse gases:
(a) allow shorter wavelengths to enter the earth's atmosphere while not allowing longer wavelengths to leave the earth's atmosphere
(b) allow longer wavelengths to enter the earth's atmosphere while not allowing shorter wavelengths to leave the surface
(c) do not have wavelength-specific character
(d) show wavelength-specific behaviour near the earth while far from earth they show wavelength-independent behaviour
Show Answer & Explanation

Answer: (a) allow shorter wavelengths to enter the earth's atmosphere while not allowing longer wavelengths to leave the earth's atmosphere

Explanation:
1. Short-wavelength solar radiation passes through the atmosphere.
2. The earth re-emits long-wavelength infrared, which greenhouse gases absorb and trap.

Teacher's Note:
1. Visible light in, infrared trapped.

Question 13: High concentration of which of the following in the atmosphere leads to stiffness of flower buds, which eventually fall off from plants?
(a) \( \ce{NO2} \)
(b) \( \ce{SO2} \)
(c) CFC
(d) smog
Show Answer & Explanation

Answer: (b) \( \ce{SO2} \)

Explanation:
1. Sulphur dioxide damages plants, causing chlorosis and making flower buds stiff so that they fall off.

Teacher's Note:
1. SO2 also causes acid rain.

Question 14: Identify the wrong statement in the following:
(a) chlorofluorocarbons are responsible for ozone layer depletion
(b) greenhouse effect is responsible for global warming
(c) acid rain is mostly because of oxides of nitrogen and sulphur
(d) the ozone layer does not permit infrared radiation from the sun to reach the earth
Show Answer & Explanation

Answer: (d) the ozone layer does not permit infrared radiation from the sun to reach the earth

Explanation:
1. The ozone layer absorbs ultraviolet radiation, not infrared radiation.
2. The other three statements are correct.

Teacher's Note:
1. Ozone absorbs UV, greenhouse gases absorb IR.

Question 15: Which one of the following statements is not true?
(a) dissolved oxygen (DO) in cold water can reach a concentration of up to 10 ppm
(b) clean water would have a BOD value of less than 5 ppm
(c) fluoride deficiency in drinking water is harmful, and soluble fluoride is often used to bring its concentration up to 1 ppm
(d) when the pH of rain water is higher than 6.5, it is called acid rain
Show Answer & Explanation

Answer: (d) when the pH of rain water is higher than 6.5, it is called acid rain

Explanation:
1. Rain water is called acid rain when its pH falls below 5.6, not above 6.5.
2. The other statements are correct.

Teacher's Note:
1. Normal rain is slightly acidic with pH about 5.6.

Question 16: Presence of which of the following fuel gases in the exhaust fumes shows incomplete combustion of the fuel?
(a) sulphur dioxide
(b) carbon monoxide and water vapour
(c) carbon monoxide
(d) nitrogen dioxide
Show Answer & Explanation

Answer: (c) carbon monoxide

Explanation:
1. Carbon monoxide forms when there is insufficient oxygen for complete oxidation of carbon.
2. Complete combustion gives \( \ce{CO2} \) only.

Teacher's Note:
1. CO is the sign of incomplete combustion.

Question 17: The irritant red haze in the traffic and congested places is due to the presence of which of the following? (i) oxides of sulphur, (ii) oxides of nitrogen, (iii) carbon dioxide, (iv) mists, smoke and dust, (v) smog
(a) (i), (iv) and (v)
(b) (iii) only
(c) (ii) only
(d) (ii) and (v)
Show Answer & Explanation

Answer: (c) (ii) only

Explanation:
1. The reddish brown colour of the haze is due to nitrogen dioxide (\( \ce{NO2} \)) from vehicle exhaust.
2. Sulphur oxides and carbon dioxide are colourless.

Teacher's Note:
1. NO2 is reddish brown.

Question 18: Which among the following statements is false?
(a) oil slick in sea water increases the D.O. value
(b) the main reason for river water pollution is industrial and domestic sewage discharge
(c) surface water contains a lot of organic matter, mineral nutrients and radioactive materials
(d) oil spill in sea water causes heavy damage to fishery
Show Answer & Explanation

Answer: (a) oil slick in sea water increases the D.O. value

Explanation:
1. An oil slick covers the water surface and cuts off the supply of oxygen, so the dissolved oxygen decreases.
2. So the statement that it increases DO is false.

Teacher's Note:
1. Oil layer stops oxygen dissolving.

Question 19: Which one of the following pairs is mismatched?
(a) fossil fuel burning - release of \( \ce{CO2} \)
(b) nuclear power - radioactive wastes
(c) solar energy - greenhouse effect
(d) biomass burning - release of \( \ce{CO2} \)
Show Answer & Explanation

Answer: (c) solar energy - greenhouse effect

Explanation:
1. Solar energy is a clean energy source and does not cause the greenhouse effect.
2. The other pairs are correct.

Teacher's Note:
1. Solar energy produces no greenhouse gases.

Question 20: In almost all Indian metropolitan cities like Delhi, the major atmospheric pollutant(s) is/are:
(a) suspended particulate matter (SPM)
(b) oxides of sulphur
(c) carbon dioxide and carbon monoxide
(d) oxides of nitrogen
Show Answer & Explanation

Answer: (a) suspended particulate matter (SPM)

Explanation:
1. Dust, soot and other suspended particulate matter from vehicles, construction and industry are the dominant pollutants in major Indian cities.

Teacher's Note:
1. SPM and PM10 levels are very high.

Question 21: Which of the following statements are not correct? (i) F- concentration above 2 ppm causes brown mottling of teeth. (ii) Excessive F- (over 10 ppm) has harmful effects on bones and teeth. (iii) Excessive lead in drinking water causes methemoglobinemia. (iv) Deficiency of sulphate in drinking water causes a laxative effect.
(a) (ii) and (iv)
(b) (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (iii) and (iv)
Show Answer & Explanation

Answer: (d) (iii) and (iv)

Explanation:
1. Statements (i) and (ii) are correct.
2. Methemoglobinemia is caused by excess nitrate, not lead, and the laxative effect is caused by excess sulphate, not deficiency.
3. So (iii) and (iv) are not correct.

Teacher's Note:
1. Nitrate gives blue baby syndrome.
2. Excess sulphate acts as a laxative.

Question 22: Which of the following statement(s) is/are true about waste recycling? (i) Clothes can be made from recycled plastic waste. (ii) Fuel that has a high octane rating and contains no lead can be obtained from plastic waste. (iii) Technology has now been developed to produce electricity from garbage.
(a) (ii) only
(b) (ii) and (iii)
(c) (iii) only
(d) all of these
Show Answer & Explanation

Answer: (d) all of these

Explanation:
1. Plastic waste can be spun into fibres for clothes, and pyrolysed into high octane lead-free fuel.
2. Waste-to-energy plants generate electricity from garbage, so all three statements are true.

Teacher's Note:
1. Recycling produces fibre, fuel and electricity.

Question 23: Which of the following is/are formed when ozone reacts with unburnt hydrocarbons in polluted air? (i) formaldehyde, (ii) acrolein, (iii) peroxyacetyl nitrate, (iv) formic acid
(a) (i) and (iv)
(b) (ii) only
(c) (iii) only
(d) (i), (ii) and (iii)
Show Answer & Explanation

Answer: (d) (i), (ii) and (iii)

Explanation:
1. Ozone reacts with unburnt hydrocarbons to give formaldehyde and acrolein, and peroxyacetyl nitrate forms from nitrogen oxides and hydrocarbons.
2. These are the main constituents of photochemical smog.

Teacher's Note:
1. They are the eye irritants of photochemical smog.

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Multiple Choice Questions (MCQs) for JEE Chemistry Environmental Chemistry

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FAQs

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