JEE Chemistry Environmental Chemistry MCQs Set 15

Multiple Choice Questions (MCQs) for JEE Chemistry: Environmental Chemistry

Access targeted multiple-choice questions for Environmental Chemistry designed to align with the latest JEE academic syllabus for JEE Chemistry. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Practice Environmental Chemistry MCQs for JEE Chemistry

View or download the dedicated Environmental Chemistry MCQ resource below. Practicing these 50 objective questions regularly builds familiarity with standard exam patterns and helps secure higher marks in final Chemistry evaluations.

Multiple Choice Questions

Question 1: The Bhopal gas tragedy was caused by the leakage of:
(a) \( \ce{CO} \)
(b) \( \ce{COCl2} \)
(c) Methyl isocyanide
(d) Methyl isocyanate
Show Answer & Explanation

Answer: (d) Methyl isocyanate

Explanation:
1. The 1984 Bhopal disaster released methyl isocyanate (\( \ce{CH3NCO} \)), a highly toxic gas used in making carbamate pesticides.

Teacher's Note:
1. Do not confuse isocyanate with isocyanide.

Question 2: A water sample of good quality will have:
(a) High dissolved oxygen (DO)
(b) High BOD
(c) High COD
(d) High BOD and high COD
Show Answer & Explanation

Answer: (a) High dissolved oxygen (DO)

Explanation:
1. Clean water is rich in dissolved oxygen, while high BOD and COD indicate a large amount of oxidisable organic matter.

Teacher's Note:
1. DO is high and BOD is low in clean water.

Question 3: The amount of oxygen required to oxidise the organic matter (biodegradable and non-biodegradable) present in water by a strong chemical oxidant is called:
(a) DO
(b) COD
(c) BOD
(d) TLV
Show Answer & Explanation

Answer: (b) COD

Explanation:
1. Chemical oxygen demand is determined with acidified potassium dichromate and measures all oxidisable organic matter.

Teacher's Note:
1. COD uses a chemical oxidant, BOD uses microbes.

Question 4: The amount of oxygen used by microorganisms present in a water sample over five days at 20 degrees C is called:
(a) COD
(b) DO
(c) TLV
(d) BOD
Show Answer & Explanation

Answer: (d) BOD

Explanation:
1. That is the standard definition of biochemical oxygen demand (BOD5).

Teacher's Note:
1. Remember five days and 20 degrees C.

Question 5: Four water samples A, B, C and D have dissolved oxygen values of 1, 3, 5 and 8 mg/L respectively. The most polluted sample is:
(a) A
(b) B
(c) C
(d) D
Show Answer & Explanation

Answer: (a) A

Explanation:
1. Pollution by organic matter uses up dissolved oxygen, so the sample with the least DO is the most polluted.

Teacher's Note:
1. Low DO means heavy organic pollution.

Question 6: The region of the atmosphere that contains the ozone layer is the:
(a) Troposphere
(b) Thermosphere
(c) Mesosphere
(d) Stratosphere
Show Answer & Explanation

Answer: (d) Stratosphere

Explanation:
1. Ozone is concentrated in the stratosphere at about 15 to 35 km above the earth, where it absorbs harmful UV radiation.

Teacher's Note:
1. Good ozone is in the stratosphere.

Question 7: Organic pollution in water is measured by:
(a) pH
(b) Salinity
(c) COD
(d) DO alone
Show Answer & Explanation

Answer: (c) COD

Explanation:
1. COD and BOD measure oxygen demand due to organic matter. pH and salinity do not measure organic load, and DO is only an indirect indicator.

Teacher's Note:
1. Oxygen demand measures organic load.

Question 8: BOD values of four water samples A, B, C and D are 60, 80, 100 and 150 mg/L respectively. The most polluted sample is:
(a) A
(b) B
(c) C
(d) D
Show Answer & Explanation

Answer: (d) D

Explanation:
1. A higher BOD means more biodegradable organic matter, so D with 150 mg/L is the most polluted.

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

Question 9: A high BOD of a river water indicates that the river is:
(a) Not polluted
(b) Polluted heavily with inorganic chemicals
(c) Heavily polluted with organic matter that microorganisms decompose
(d) Polluted with pesticides
Show Answer & Explanation

Answer: (c) Heavily polluted with organic matter that microorganisms decompose

Explanation:
1. BOD is the oxygen consumed by microorganisms while decomposing organic matter, so a high value means a large amount of organic waste.

Teacher's Note:
1. BOD links microbes and organic matter.

Question 10: Which of the following can cause depletion of the ozone layer?
(a) \( \ce{H2S} \)
(b) \( \ce{NO} \)
(c) Smoke
(d) Aerosols of water
Show Answer & Explanation

Answer: (b) \( \ce{NO} \)

Explanation:
1. \( \ce{NO + O3 -> NO2 + O2} \), so nitric oxide from supersonic aircraft destroys ozone.

Teacher's Note:
1. Oxides of nitrogen and CFCs deplete ozone.

Question 11: The hottest region of the atmosphere is the:
(a) Mesosphere
(b) Stratosphere
(c) Thermosphere
(d) Troposphere
Show Answer & Explanation

Answer: (c) Thermosphere

Explanation:
1. Temperature rises steeply in the thermosphere because of absorption of solar X-rays and short-wave UV by oxygen and nitrogen.

Teacher's Note:
1. Thermosphere has the highest temperatures.

Question 12: The minimum level of a pollutant above which a healthy worker is adversely affected on 8 hours daily exposure is called:
(a) Critical limit value
(b) Toxic limit value
(c) Threshold limit value (TLV)
(d) Dangerous limit value
Show Answer & Explanation

Answer: (c) Threshold limit value (TLV)

Explanation:
1. TLV is the permissible concentration that a worker can tolerate for an 8-hour working day.

Teacher's Note:
1. TLV is a workplace safety limit.

Question 13: Which of the following is a secondary air pollutant?
(a) \( \ce{CO} \)
(b) Hydrocarbons
(c) PAN
(d) \( \ce{NO} \)
Show Answer & Explanation

Answer: (c) PAN

Explanation:
1. Peroxyacetyl nitrate is formed in the atmosphere by reactions between primary pollutants (hydrocarbons and nitrogen oxides) in sunlight.

Teacher's Note:
1. Secondary pollutants form in the air.

Question 14: Carbon monoxide is poisonous because it:
(a) Combines with oxygen of the body to form \( \ce{CO2} \)
(b) Combines with haemoglobin and makes it incapable of carrying oxygen
(c) Reduces organic matter of tissues
(d) Dries up the blood
Show Answer & Explanation

Answer: (b) Combines with haemoglobin and makes it incapable of carrying oxygen

Explanation:
1. CO binds to haemoglobin about 200 times more strongly than oxygen, forming carboxyhaemoglobin.

Teacher's Note:
1. Carboxyhaemoglobin blocks oxygen transport.

Question 15: Incomplete combustion of petrol in an automobile engine can be detected by testing the exhaust gases for:
(a) \( \ce{CO2} \) and \( \ce{H2O} \)
(b) \( \ce{CO} \)
(c) \( \ce{NO2} \)
(d) \( \ce{SO2} \)
Show Answer & Explanation

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

Explanation:
1. Carbon forms CO rather than \( \ce{CO2} \) when there is a shortage of oxygen.

Teacher's Note:
1. Incomplete combustion gives CO.

Question 16: The irritant red haze seen in traffic and congested places is due to oxides of:
(a) Nitrogen
(b) Carbon
(c) Sulphur
(d) All of these
Show Answer & Explanation

Answer: (a) Nitrogen

Explanation:
1. Brown-red \( \ce{NO2} \) is formed in vehicle engines and gives the reddish-brown haze.

Teacher's Note:
1. NO2 is a brown gas.

Question 17: Fly ash is a contaminant of air mainly due to:
(a) Thermal power plants
(b) Nuclear power plants
(c) Electrolytic refining of metals
(d) Hydroelectric power plants
Show Answer & Explanation

Answer: (a) Thermal power plants

Explanation:
1. Burning of coal in thermal power stations releases fine non-combustible ash.

Teacher's Note:
1. Fly ash comes from burning coal.

Question 18: Acid rain is due to oxides of:
(a) Phosphorus
(b) Nitrogen
(c) Sulphur
(d) Both nitrogen and sulphur
Show Answer & Explanation

Answer: (d) Both nitrogen and sulphur

Explanation:
1. \( \ce{SO2} \) and \( \ce{NO2} \) form \( \ce{H2SO4} \) and \( \ce{HNO3} \) in the atmosphere, lowering the pH of rain below 5.6.

Teacher's Note:
1. Rain with pH below 5.6 is acid rain.

Question 19: Classical (London) smog occurs in:
(a) Cool climate
(b) Humid climate
(c) Cool and humid climate
(d) Hot and humid climate
Show Answer & Explanation

Answer: (c) Cool and humid climate

Explanation:
1. Classical smog is a mixture of smoke, fog and \( \ce{SO2} \) and occurs in cool, humid weather. It is reducing in nature.

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

Question 20: PAN, an important constituent of photochemical smog, is formed by the action of \( \ce{NO2} \) and \( \ce{O3} \) on:
(a) Unburnt hydrocarbons
(b) Aldehydes
(c) Pesticides
(d) Herbicides
Show Answer & Explanation

Answer: (a) Unburnt hydrocarbons

Explanation:
1. Unburnt hydrocarbons are oxidised in sunlight to free radicals that combine with \( \ce{NO2} \) to give peroxyacetyl nitrate.

Teacher's Note:
1. Smog needs sunlight, NOx and hydrocarbons.

Question 21: Depletion of the ozone layer is NOT caused by:
(a) \( \ce{Cl2} \)
(b) \( \ce{NO} \)
(c) Chlorofluorocarbons
(d) \( \ce{CO} \)
Show Answer & Explanation

Answer: (d) \( \ce{CO} \)

Explanation:
1. Chlorine atoms, nitric oxide and CFCs catalytically destroy ozone, but CO does not.

Teacher's Note:
1. CO is a toxic gas but not an ozone depleter.

Question 22: Eutrophication in lakes takes place due to:
(a) Excess dissolved oxygen
(b) Increase in soil pH
(c) Large concentrations of phosphate nutrients in water
(d) Dissolved fluorides
Show Answer & Explanation

Answer: (c) Large concentrations of phosphate nutrients in water

Explanation:
1. Phosphate and nitrate nutrients cause algal blooms, whose decay uses up dissolved oxygen.

Teacher's Note:
1. Nutrients cause algal bloom and oxygen loss.

Question 23: The increase in concentration of a pesticide at successive levels of a food chain is called:
(a) Eutrophication
(b) Biomagnification (bioamplification)
(c) Chemical amplification
(d) Biological pollution
Show Answer & Explanation

Answer: (b) Biomagnification (bioamplification)

Explanation:
1. Non-degradable pollutants such as DDT accumulate and become more concentrated in higher animals.

Teacher's Note:
1. DDT is a classic example.

Question 24: The pH of a fertile soil is likely to be:
(a) 3
(b) 9
(c) 6 to 7
(d) 14
Show Answer & Explanation

Answer: (c) 6 to 7

Explanation:
1. Most crop plants and soil organisms grow best in nearly neutral soil, with pH between about 6 and 7.

Teacher's Note:
1. Fertile soil is close to neutral.

Question 25: Which oxidant is used for determining the COD of a water sample in the laboratory?
(a) \( \ce{KNO3} \)
(b) \( \ce{KMnO4} \)
(c) Oxalic acid
(d) \( \ce{K2Cr2O7} \) with 50% \( \ce{H2SO4} \)
Show Answer & Explanation

Answer: (d) \( \ce{K2Cr2O7} \) with 50% \( \ce{H2SO4} \)

Explanation:
1. Acidified potassium dichromate oxidises almost all organic matter and the unused dichromate is titrated.

Teacher's Note:
1. Dichromate is the COD oxidant.

Question 26: The lowest layer of the atmosphere, extending up to about 10 km, is called the:
(a) Stratosphere
(b) Troposphere
(c) Mesosphere
(d) Hydrosphere
Show Answer & Explanation

Answer: (b) Troposphere

Explanation:
1. The troposphere contains most of the air and water vapour and is where weather occurs.

Teacher's Note:
1. Troposphere means lowest layer.

Free study material for Chemistry

Multiple Choice Questions (MCQs) for JEE Chemistry Environmental Chemistry

JEE Chemistry Environmental Chemistry Objective Test Questions

Test your conceptual understanding of Environmental Chemistry with these targeted multiple-choice questions. Designed in alignment with the latest JEE curriculum for JEE Chemistry, these problem sets build accuracy and prepare students for objective exams.

NCERT-Aligned Objective Questions and Solutions

Built using the official NCERT book for JEE, these Chemistry objective sets provide reliable academic guidance. Pair your practice with our recommended NCERT solutions to master optimal problem-solving approaches.

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FAQs

Where can I access latest JEE Chemistry Environmental Chemistry MCQs Set 15?

You can get most exhaustive JEE Chemistry Environmental Chemistry MCQs Set 15 for free on StudiesToday.com. These MCQs for JEE Chemistry are updated for the 2026-27 academic session as per JEE examination standards.

Are Assertion-Reasoning and Case-Study MCQs included in the Chemistry JEE material?

Yes, our JEE Chemistry Environmental Chemistry MCQs Set 15 include the latest type of questions, such as Assertion-Reasoning and Case-based MCQs. 50% of the JEE paper is now competency-based.

How do practicing Chemistry MCQs help in scoring full marks in JEE exams?

By solving our JEE Chemistry Environmental Chemistry MCQs Set 15, JEE students can improve their accuracy and speed which is important as objective questions provide a chance to secure 100% marks in the Chemistry.

Do you provide answers and explanations for JEE Chemistry Environmental Chemistry MCQs Set 15?

Yes, Chemistry MCQs for JEE have answer key and brief explanations to help students understand logic behind the correct option as its important for 2026 competency-focused JEE exams.

Can I practice these Chemistry JEE MCQs online?

Yes, you can also access online interactive tests for JEE Chemistry Environmental Chemistry MCQs Set 15 on StudiesToday.com as they provide instant answers and score to help you track your progress in Chemistry.