Environment Chemistry Previous Year Questions with Solutions

1.0Introduction (Environmental Chemistry)

Environmental Chemistry is the study of chemical processes in the environment—air, water, soil, and living organisms—and how pollutants affect them. It involves understanding the sources, reactions, transport, and effects of chemical species in both natural and polluted environments.

2.0Major Types of Pollution

Atmospheric Pollution (Troposphere)

• Gaseous Pollutants:
  Sulfur Dioxide (SO₂): From burning sulfur-rich fuels; causes respiratory issues and acid rain.
  Nitrogen Oxides (NOx): From combustion; leads to smog and respiratory problems.
  Hydrocarbons: From vehicles; can cause cancer.
  Carbon Monoxide (CO): Toxic; inhibits oxygen transport.
  Carbon Dioxide (CO₂): Major greenhouse gas causing global warming.
• Particulates: Dust, mist, smoke, and smog affect air quality and health.
• Smog:
  Classical: Smoke + fog + SO₂ (reducing nature).
  Photochemical: Sunlight + emissions → Ozone, NO₂ (oxidizing, harmful).
• Control: Catalytic converters, pollution-absorbing trees.

Stratospheric Pollution

• Focuses on ozone layer depletion by CFCs and other ODS.
  Formation of Ozone: O₂ absorbs UV, forms O₃.
  Depletion Effects: Skin aging, cataracts, cancer, ecosystem damage.

Water Pollution

• Causes: Industrial discharge, agricultural runoff, pathogens, and chemicals.
• BOD: Indicates organic pollution level (clean water < 5 ppm).
• Eutrophication: Algal blooms reduce oxygen, harm aquatic life.

Soil Pollution

• Sources: Pesticides, fertilizers, industrial waste, solid waste, mining.
• Pesticides: Include herbicides, insecticides, fungicides, rodenticides.
• Industrial Waste:
  Biodegradable: From food/textile/paper industries.
  Non-biodegradable: Fly ash, slag, metal mud.
• Waste Management:
  Swachh Bharat Mission (SBM): Cleanliness drive.
  SBM-U: Urban sanitation.
  SBM-G: Rural hygiene.

3.0Green Chemistry

Aims to reduce pollution by using eco-friendly methods:

• Examples:
  Dry cleaning: CO₂ replaces tetrachloroethene.
  Paper bleaching: H₂O₂ replaces Cl₂.
  Synthesis: Ionic catalysts in water.
  Water treatment: Tamarind seed powder used.

Applications of Environmental Chemistry include pollution control, sustainable resource use, and promoting health through eco-friendly practices.

Q.1  Match List-I with List-II :

(1) A-III, B-IV, C-I, D-II

(2) A-IV, B-III, C-II, D-I

(3) A-I, B-II, C-III, D-IV

(4) A-III, B-II, C-I, D-IV

Ans.  A-III, B-IV, C-I, D-II

Solution: 

A) F(-) → < 2ppm 

B) SO₄^2- → < 500ppm

C) NO₃^2- → < 50ppm

D) Zn → < 5ppm 

Q.2 Given below are two statements:

Statement I : The non bio-degradable fly ash and slag from steel industry can be used by the cement industry.

Statement II : The fuel obtained from plastic waste is lead free.

In the light of the above statements, choose the most appropriate answer from the options given below:

(1) Both Statement I and Statement II are correct

(2) Both Statement I and Statement II are  incorrect

(3) Statement I is correct but Statement II is incorrect

(4) Statement I is incorrect but Statement II is    correct

Ans. (1)

Solution. 

(I) Fly ash and slag from steel industry are utilised by cement industry.

(II) Fuel obtained from plastic waste has high octane rating. It contains no lead and it is known as green fuel.

Both statements (I) & (II) are correct.

Q.3 Which one of the following techniques is not used to spot components of a  mixture separated on a thin layer chromatographic plate?

(1) I₂ (Solid)

(2) U.V. Light

(3) Visualisation agent as a component of mobile phase

(4) Spraying of an appropriate reagent

Ans. (C)  Visualisation agent as a component of mobile phase

Q 4. Which of the following statement(s) is (are) incorrect reason for eutrophication ?

(A) excess usage of fertilisers

(B) excess usage of detergents

(C) dense plant population in water bodies

(D) lack of nutrients in water bodies that prevent plant growth

Choose the most appropriate answer from the options given below :

(1) (A) only                                                       (2) (C) only

(3) (B) and (D) only                                          (4) (D) only

Ans (4)

Solution.

The process in which nutrient enriched water bodies support a dense plant population which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as eutrophication.

Q.5 The gas 'A' is having very low reactivity reaches to stratosphere. It is non–toxic and non–flammable but dissociated by UV—radiations in stratosphere. The intermediates formed initially from the gas 'A' are :

$$\begin{gathered} 1)Cl\dot{O}+\dot{C}{F}_{2}Cl \\ 2)Cl\dot{O}+C{\dot{H}}_2 \\ 3)\dot{C}{H}_3+C{\dot{F}}_{2}Cl \\ 4)\dot{C}l+C{\dot{F}}_{2}Cl \end{gathered}$$

Q.6 BOD values (in ppm) for clean water (A) and polluted water (B) are expected respectively :

(1) A > 50, B < 27      (2) A > 25, B < 17

(3) A < 5, B > 17        (4) A > 15, B > 47

Ans. (3)

Solution.

BOD values of clean water (A) is less than 5 ppm

So      A < 5

BOD values of polluted water (B is greater than 17 ppm

So     B > 17

Hence Ans. is 3

Q.7 Biochemical Oxygen Demand (BOD) is the amount of oxygen required (in ppm):

(1) by anaerobic bacteria to breakdown inorganic waste present in a water body.

(2) for the photochemical breakdown of waste present in 1 m³ volume of a water body.

(3) by bacteria to break-down organic waste in a certain volume of a water sample.

(4) for sustaining life in a water body.

Ans. (3)

Sol. Biochemical oxygen demand (BOD) is amount of oxygen required by bacteria to break down organic waste in a certain volume of water sample.

Q.8 The normal rain water is slightly acidic and its pH value is 5.6 because of which one of the following?

(1) CO₂ + H₂O → H₂CO₃

(2) 4NO₂ + O₂ +H₂O → 4HNO₃

(3) 2SO₂ + O₂ +H₂O → 2H₂SO₄

(4) N₂O₅ + H₂O → 2HNO₃

Ans. (1)

Sol. We are aware that normally rain water has a pH of 5.6 due to the presence of H⁺ ions formed by the reactions of rain water with carbon dioxide present in the atmosphere.

H₂O(l) +CO₂(g) → H₂CO₃(aq)

H₂CO₃(aq) ⇆ H⁺(aq) + HCO^-₃(aq)

Q. 9 Which of the following compounds is an example of Freon?

(1) C₂Cl₂F₂                                         (2) C₂HF₃

(3) C₂H₂F₂                           (4) C₂F₄

Ans. (1)

Sol. Freons are chlorofluoro carbon