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Environmental Chemistry — GK Questions with Answers

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36 questions
  1. In which layer of the atmosphere is the ozone layer?
    1. Troposphere
    2. Stratosphere
    3. Mesosphere
    4. Thermosphere
    Show answer

    Answer: (B) Stratosphere

    The ozone layer is at ≈ 15–35 km in the stratosphere; that is why temperature rises with height there.

  2. In which layer of the atmosphere do meteors burn up?
    1. Troposphere
    2. Stratosphere
    3. Exosphere
    4. Mesosphere
    Show answer

    Answer: (D) Mesosphere

    In the mesosphere (≈ 50–80 km) friction with air burns the meteors.

  3. The third most plentiful gas in dry air?
    1. Argon
    2. CO₂
    3. Neon
    4. Hydrogen
    Show answer

    Answer: (A) Argon

    N₂ 78%, O₂ 21%, Ar 0.93% — CO₂ only ≈ 0.04%.

  4. Total ozone is measured in which unit?
    1. Decibel
    2. Sievert
    3. Dobson unit
    4. ppm
    Show answer

    Answer: (C) Dobson unit

    Normal ≈ 300 DU; below 220 DU is an ozone hole.

  5. Which of these is a secondary air pollutant?
    1. SO₂
    2. CO
    3. PAN
    4. NO
    Show answer

    Answer: (C) PAN

    PAN and ground-level ozone form by photochemical reactions of primary pollutants.

  6. Why is CO poisonous?
    1. It binds haemoglobin forming carboxyhaemoglobin
    2. It burns the lungs
    3. It forms acid
    4. It is radioactive
    Show answer

    Answer: (A) It binds haemoglobin forming carboxyhaemoglobin

    CO binds haemoglobin ≈ 200–250 times more strongly than O₂ — the blood cannot carry oxygen.

  7. The main source of sulphur dioxide?
    1. Petrol in vehicles
    2. Fridges
    3. Paddy fields
    4. Coal-burning power stations
    Show answer

    Answer: (D) Coal-burning power stations

    Coal and diesel contain sulphur: S + O₂ → SO₂.

  8. Which particles reach deep into the lungs and the blood?
    1. PM10
    2. PM2.5
    3. Sand
    4. Pollen
    Show answer

    Answer: (B) PM2.5

    Fine particles smaller than 2.5 µm go deep — so they are more dangerous.

  9. When did India’s National Air Quality Index start?
    1. 2014
    2. 2010
    3. 2017
    4. 2019
    Show answer

    Answer: (A) 2014

    On 17 October 2014, based on 8 pollutants.

  10. The pH of normal (unpolluted) rain is about?
    1. 7.0
    2. 6.5
    3. 5.6
    4. 4.0
    Show answer

    Answer: (C) 5.6

    CO₂ of the air dissolves to form carbonic acid; acid rain has a pH below 5.6.

  1. The "marble cancer" of the Taj Mahal comes from which reaction?
    1. CaO + H₂O → Ca(OH)₂
    2. CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂
    3. CaCO₃ → CaO + CO₂
    4. 2Ca + O₂ → 2CaO
    Show answer

    Answer: (B) CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂

    Sulphuric acid of acid rain turns marble (CaCO₃) into CaSO₄ and dissolves it.

  2. Greenhouse gases mainly hold back which rays?
    1. Ultraviolet
    2. Visible
    3. X-rays
    4. Infrared
    Show answer

    Answer: (D) Infrared

    The infrared (heat) going back from the Earth is absorbed and sent back down.

  3. Which of these has the highest global warming potential (GWP)?
    1. CO₂
    2. CH₄
    3. N₂O
    4. SF₆
    Show answer

    Answer: (D) SF₆

    SF₆ ≈ 23,500; N₂O ≈ 265, CH₄ ≈ 28, CO₂ = 1.

  4. In which year was the Paris Agreement made?
    1. 1992
    2. 2015
    3. 1997
    4. 2021
    Show answer

    Answer: (B) 2015

    COP21, 2015 — the aim is to keep warming well below 2 °C.

  5. The chemical nature of classical (London) smog?
    1. Oxidising
    2. Neutral
    3. Reducing
    4. Basic
    Show answer

    Answer: (C) Reducing

    The smog of SO₂ and smoke in cold, damp weather is reducing; photochemical smog is oxidising.

  6. Primary pollutants of photochemical smog?
    1. NOₓ and hydrocarbons
    2. SO₂ and smoke
    3. CO₂ and water vapour
    4. CFCs and halons
    Show answer

    Answer: (A) NOₓ and hydrocarbons

    NOₓ and hydrocarbons form O₃, PAN and HCHO in sunlight.

  7. Why does one chlorine atom work again and again in ozone depletion?
    1. It makes ozone
    2. It is not destroyed; it comes back from ClO•
    3. It makes CO₂
    4. It is heavy
    Show answer

    Answer: (B) It is not destroyed; it comes back from ClO•

    Cl• + O₃ → ClO• + O₂; ClO• + O → Cl• + O₂ — like a catalyst.

  8. When is the Antarctic ozone hole largest?
    1. June–July
    2. March
    3. December–January
    4. September–October
    Show answer

    Answer: (D) September–October

    In the southern spring, when the Sun returns, chlorine stored on PSCs becomes active.

  9. The Kigali Amendment deals with cutting which substances?
    1. HFCs
    2. CFCs
    3. CO₂
    4. Mercury
    Show answer

    Answer: (A) HFCs

    HFCs do not destroy ozone but are strong greenhouse gases; Kigali 2016.

  10. BOD of highly polluted water is about?
    1. 1 ppm
    2. 3 ppm
    3. 17 ppm or more
    4. 0.1 ppm
    Show answer

    Answer: (C) 17 ppm or more

    BOD of clean water is below 5 ppm, of highly polluted water 17 ppm or more.

  1. Correct statement about COD and BOD?
    1. COD is always less than BOD
    2. Both are equal
    3. COD is always more than BOD
    4. No relation
    Show answer

    Answer: (C) COD is always more than BOD

    COD also counts substances that microbes cannot break down.

  2. The main cause of eutrophication in lakes?
    1. Nitrate and phosphate
    2. Mercury
    3. Oxygen
    4. Salt
    Show answer

    Answer: (A) Nitrate and phosphate

    Nutrients from fertilisers and detergents cause an algal bloom, then oxygen falls.

  3. Minamata disease is caused by which metal?
    1. Cadmium
    2. Lead
    3. Arsenic
    4. Mercury
    Show answer

    Answer: (D) Mercury

    From eating fish with methylmercury — Japan, 1956.

  4. Itai-itai disease is linked with?
    1. Mercury
    2. Cadmium
    3. Fluoride
    4. Nitrate
    Show answer

    Answer: (B) Cadmium

    Cadmium makes bones brittle and painful — the Jinzu River in Japan.

  5. Which disease comes from too much nitrate in drinking water?
    1. Blue baby syndrome
    2. Fluorosis
    3. Goitre
    4. Rickets
    Show answer

    Answer: (A) Blue baby syndrome

    Methaemoglobinaemia in infants; the nitrate limit in IS 10500 is 45 mg/L.

  6. The maximum permissible limit of fluoride in drinking water?
    1. 0.5 mg/L
    2. 5 mg/L
    3. 1.5 mg/L
    4. 45 mg/L
    Show answer

    Answer: (C) 1.5 mg/L

    Acceptable 1.0, permissible without an alternative 1.5 mg/L; above this, fluorosis.

  7. The real disinfectant when water is disinfected with chlorine?
    1. HCl
    2. HOCl
    3. Cl⁻
    4. O₃
    Show answer

    Answer: (B) HOCl

    Cl₂ + H₂O → HCl + HOCl; HOCl oxidises the germs.

  8. In an aquatic food chain the DDT level is highest in?
    1. Water
    2. Plankton
    3. Small fish
    4. Fish-eating birds
    Show answer

    Answer: (D) Fish-eating birds

    Biomagnification — from 0.003 ppb in water to ≈ 25 ppm in birds.

  9. Which gas leaked in the Bhopal gas tragedy?
    1. Phosgene
    2. Ammonia
    3. Chlorine
    4. Methyl isocyanate
    Show answer

    Answer: (D) Methyl isocyanate

    ≈ 40 tonnes of MIC from Union Carbide’s pesticide plant, 2–3 December 1984.

  10. India’s "umbrella" environmental law?
    1. Water Act 1974
    2. Environment (Protection) Act 1986
    3. Air Act 1981
    4. Forest Act 1980
    Show answer

    Answer: (B) Environment (Protection) Act 1986

    Made after Bhopal; noise, plastic and e-waste rules come under it.

  1. When was the National Green Tribunal (NGT) set up?
    1. 1986
    2. 2002
    3. 2010
    4. 2014
    Show answer

    Answer: (C) 2010

    NGT Act 2010; principal bench in Delhi.

  2. In green chemistry, what is used for dry cleaning?
    1. Liquid CO₂
    2. Tetrachloroethene
    3. Benzene
    4. CCl₄
    Show answer

    Answer: (A) Liquid CO₂

    Liquid CO₂ with a suitable detergent — instead of a chlorinated solvent.

  3. Which metals are in a vehicle’s catalytic converter?
    1. Fe, Cu
    2. Pt, Pd, Rh
    3. Na, K
    4. Pb, Sn
    Show answer

    Answer: (B) Pt, Pd, Rh

    They turn CO, NOₓ and hydrocarbons into CO₂, N₂ and H₂O.

  4. Iodine-131 affects which organ of the body?
    1. Bones
    2. Muscles
    3. Lungs
    4. Thyroid
    Show answer

    Answer: (D) Thyroid

    I-131 collects in the thyroid; Sr-90 in bones, Cs-137 in muscles.

  5. By the Noise Pollution Rules 2000, the day limit in a silence zone is?
    1. 50 dB
    2. 40 dB
    3. 55 dB
    4. 75 dB
    Show answer

    Answer: (A) 50 dB

    Silence zone 50 by day, 40 dB by night; residential 55/45.

  6. Why is thermal pollution harmful to aquatic life?
    1. The water turns salty
    2. The water freezes
    3. Hot water holds less oxygen
    4. Light is reduced
    Show answer

    Answer: (C) Hot water holds less oxygen

    The solubility of gases falls as temperature rises, while fish need more oxygen.

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