ENVIRONMENTAL CHEMISTRY MCQs for JEE CHEMISTRY — Medium, Page 3

61 Medium

61 of 71

Remembering +4 | -1

Phosphate pollution is caused by

View answer and explanation

Correct option: D

Sewage and agricultural fertilizers

Option D (Sewage and agricultural fertilizers) is correct because these are the primary sources of phosphate pollution in water bodies.

Solution approach

Correct Answer + Core Reason: Sewage and agricultural fertilizers. These are the main sources of phosphate pollution.

Step-by-Step Solution:
Step 1: Identify sources of phosphate pollution: Phosphate pollution primarily arises from human activities.
Step 2: Consider sewage: Untreated sewage contains phosphates from detergents and human waste.
Step 3: Consider agricultural fertilizers: Agricultural fertilizers contain phosphates to promote plant growth.
Step 4: Analyze the impact: Excess phosphates in water bodies lead to eutrophication.

Why other options are wrong:
- Option A: Weathering of phosphate rocks contributes to phosphate levels, but is not the primary cause of pollution.
- Option B: Agricultural fertilizers are a significant contributor, but not the only one.
- Option C: Phosphate rocks contribute, but sewage is also a major factor.

Key Concepts:
- Phosphate pollution
- Eutrophication
- Sources of water pollution

Memory Aids:
- Think of fertilizers and sewage as major sources of nutrients in water.

Quick Tips:
- Consider the human impact on the environment when identifying pollution sources.

62 Medium

62 of 71

Remembering +4 | -1

The instrument used for measuring soil salinity is

View answer and explanation

Correct option: C

Conductivitymeter

Option C (Conductivitymeter) is correct because a conductivity meter measures the electrical conductivity of the soil, which is directly related to its salinity.

Solution approach

Correct Answer + Core Reason: Conductivitymeter. Soil salinity is measured by determining its electrical conductivity.

Step-by-Step Solution:

Step 1: Understand the concept of soil salinity.

Step 2: Soil salinity refers to the concentration of soluble salts in the soil.

Step 3: Electrical conductivity is directly proportional to the concentration of ions in the soil.

Step 4: A conductivity meter measures the electrical conductivity of the soil.

Why other options are wrong:
- Option A: Photometer measures light intensity.
- Option B: Voltameter measures voltage.
- Option D: Calorimeter measures heat.

Key Concepts:
- Soil salinity
- Electrical conductivity

Memory Aids:
- Conductivity = Salinity

Quick Tips:
- Relate the instrument to the property being measured.

63 Medium

63 of 71

Remembering +4 | -1

Burning of fossil fuels is the main source of

View answer and explanation

Correct option: D

Sulphur dioxide

Option D (Sulphur dioxide) is correct because burning fossil fuels releases sulphur dioxide, a major air pollutant.

Solution approach

Correct Answer + Core Reason: Sulphur dioxide. Burning fossil fuels releases sulphur dioxide ( $SO_2$ ), which is a major air pollutant.

Step-by-Step Solution:

Step 1: Identify the components of fossil fuels.\nFossil fuels contain carbon, hydrogen, and often sulfur.

Step 2: Determine the products of combustion.\nCombustion of fossil fuels produces carbon dioxide, water, and sulfur dioxide (if sulfur is present).

Step 3: Recognize the main source of sulfur dioxide.\nThe main source of sulfur dioxide is the burning of fossil fuels containing sulfur.

Why other options are wrong:
- Option A: Nitrogen oxide is produced during combustion, but not as the main product from burning fossil fuels.
- Option B: Nitric oxide is produced during combustion, but not as the main product from burning fossil fuels.
- Option C: Nitrous oxide is a greenhouse gas, but not the main product from burning fossil fuels.

Key Concepts:
- Air pollution
- Combustion
- Fossil fuels
- Sulfur dioxide

Memory Aids:
- Remember that burning fossil fuels releases sulfur dioxide.

Quick Tips:
- Sulfur dioxide contributes to acid rain and respiratory problems.

64 Medium

64 of 71

Understanding +4 | -1

S-I: Photo chemical smog is oxidising in nature.
S-II: Photochemical smog contains

N O

and

O_3

, formed during sequence of reactions.

View answer and explanation

Correct option: A

Both S-I

\&

S-II are correct

Option A is correct because photochemical smog is indeed oxidizing in nature and contains NO and O3, which are formed during the sequence of reactions.

Solution approach

Correct Answer + Core Reason: Both S-I $\& S-II are correct. Photochemical smog is oxidizing and contains NO and O3.\n\n**Step-by-Step Solution:**\n\n**Step 1:** Analyze Statement I. Photochemical smog is known to be oxidizing in nature due to the presence of ozone and other oxidizing agents.\n\n**Step 2:** Analyze Statement II. Photochemical smog does contain NO and O3, which are formed during the complex sequence of reactions involving nitrogen oxides and volatile organic compounds in the presence of sunlight.\n\n**Step 3:** Conclusion: Both statements are correct.\n\n**Why other options are wrong:**\n- **Option B:** Both statements are correct, so this is incorrect.\n- **Option C:** Statement II is correct, so this is incorrect.\n- **Option D:** Statement I is correct, so this is incorrect.\n\n**Key Concepts:**\n- Photochemical smog\n- Air pollution\n- Oxidizing agents\n\n**Memory Aids:**\n- Remember that photochemical smog is formed by the action of sunlight on pollutants.\n\n**Quick Tips:**\n- Know the components and effects of different types of air pollution.$

65 Medium

65 of 71

Remembering +4 | -1

______is the uppermost region of the earth atmosphere.

View answer and explanation

Correct option: C

Exosphere

Option C (Exosphere) is correct because the exosphere is the outermost layer of Earth's atmosphere, extending from the thermosphere to outer space.

Solution approach

Correct Answer + Core Reason: Exosphere. The exosphere is the uppermost region of the Earth's atmosphere.

Step-by-Step Solution:

Step 1: Recall the layers of the Earth's atmosphere in order from the surface upwards: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.

Step 2: Identify the uppermost layer. The exosphere is the outermost layer of the atmosphere.

Why other options are wrong:
- Option A: Stratosphere is the second layer of the atmosphere.
- Option B: Troposphere is the lowest layer of the atmosphere.
- Option D: Ionosphere is a region within the thermosphere and mesosphere, not a distinct layer.

Key Concepts:
- Earth's atmosphere
- Layers of the atmosphere

Memory Aids:
- Remember the order of the atmospheric layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.

Quick Tips:
- Know the characteristics of each atmospheric layer.

66 Medium

66 of 71

Remembering +4 | -1

The region containing water vapour is

View answer and explanation

Correct option: C

troposphere

Option C (troposphere) is correct because the troposphere is the lowest layer of the atmosphere and contains most of the water vapor.

Solution approach

Correct Answer + Core Reason: troposphere. The troposphere is the atmospheric layer closest to the Earth's surface and contains the majority of water vapor.

Step-by-Step Solution:
Step 1: The question asks which atmospheric layer contains water vapor.
Step 2: Key Concept: The atmosphere is divided into several layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
Step 3: The troposphere is the layer closest to the Earth's surface. It contains about 75-80% of the total mass of the atmosphere and virtually all of the water vapor.

Why other options are wrong:
- Option A: Incorrect. The thermosphere is a very high layer with very little water vapor.
- Option B: Incorrect. The stratosphere is above the troposphere and contains very little water vapor.
- Option D: Incorrect. The mesosphere is above the stratosphere and contains negligible water vapor.

Key Concepts:
- Atmospheric layers (troposphere, stratosphere, mesosphere, thermosphere)
- Composition of atmospheric layers

Memory Aids:
- Troposphere: closest to the ground, contains the most water vapor.

Quick Tips:
- Remember the order of atmospheric layers.

67 Medium

67 of 71

Remembering +4 | -1

Which of the following is not a herbicide?

View answer and explanation

Correct option: C

Polyphosphate

Option C (Polyphosphate) is correct because sodium chlorate, sodium arsenite, and triazines are all known herbicides, while polyphosphate is not.

Solution approach

Correct Answer + Core Reason: Polyphosphate is not a herbicide, unlike the other options.

Step-by-Step Solution:

Step 1: Identify the definition of a herbicide. Herbicides are substances used to kill unwanted plants (weeds).

Step 2: Consider each option:
- Sodium chlorate: Known herbicide.
- Sodium arsenite: Known herbicide.
- Polyphosphate: Not typically used as a herbicide. Used in fertilizers and water treatment.
- Triazines: Known herbicide.

Step 3: Conclude that polyphosphate is the only option that is not a herbicide.

Why other options are wrong:
- Option A: Sodium chlorate is a well-known herbicide.
- Option B: Sodium arsenite is a herbicide, although its use is restricted due to toxicity.
- Option D: Triazines are a class of herbicides commonly used in agriculture.

Key Concepts:
- Herbicides
- Chemical properties of different compounds

Memory Aids:
- None applicable

Quick Tips:
- Familiarize yourself with common herbicides and their uses.

68 Medium

68 of 71

Remembering +4 | -1

Classical smog occurs in places of

View answer and explanation

Correct option: B

Low temperature

Option B is correct because classical smog, also known as reducing smog, is prevalent in areas with low temperatures and high levels of sulfur dioxide.

Solution approach

Correct Answer + Core Reason: Low temperature. Classical smog occurs in places of low temperature.

Step-by-Step Solution:

Step 1: Define classical smog. Classical smog is also known as reducing smog and is characterized by high concentrations of sulfur dioxide and particulate matter.

Step 2: Identify conditions for classical smog. It typically occurs in cool, humid climates.

Step 3: Explain the temperature dependence. Low temperatures favor the formation and persistence of classical smog.

Why other options are wrong:
- Option A: While excess $\mathrm{S}{\mathrm{O}_2}$ is a component of classical smog, it's not the only factor. Low temperature is also crucial.
- Option C: High temperature is associated with photochemical smog, not classical smog.
- Option D: Excess $\mathrm{N}{\mathrm{H}_3}$ is not a primary component of classical smog.

Key Concepts:
- Environmental chemistry
- Smog formation
- Classical smog

Memory Aids:
- Classical smog: Think "cool and coal" (associated with burning coal, which releases sulfur dioxide).

Quick Tips:
- Distinguish between classical smog (reducing smog) and photochemical smog (oxidizing smog).

69 Medium

69 of 71

Remembering +4 | -1

The viable particulate among the following is

View answer and explanation

Correct option: B

algae

Option B (algae) is correct because algae are living organisms that can be dispersed in the atmosphere as viable particulates.

Solution approach

Correct Answer + Core Reason: algae. Algae are minute living organisms dispersed in the atmosphere as viable particulates.

Step-by-Step Solution:
Step 1: Define viable particulates.
Step 2: Viable particulates are minute living organisms dispersed in the atmosphere.
Step 3: Algae are an example of viable particulates.

Why other options are wrong:
- Option A: Fumes are condensed vapors or gases, not living organisms.
- Option C: Smoke is a mixture of solid and liquid particles, not living organisms.
- Option D: Mist is a suspension of liquid droplets, not living organisms.

Key Concepts:
- Viable particulates
- Air pollution

Memory Aids:
- Remember that viable particulates are living organisms.

Quick Tips:
- Know the different types of air pollutants.

70 Medium

70 of 71

Remembering +4 | -1

Gas released during Bhopal tragedy was

View answer and explanation

Correct option: A

Methyl isocyanate

Option A (Methyl isocyanate) is correct because the gas released during the Bhopal tragedy was methyl isocyanate (MIC), a highly toxic chemical.

Solution approach

Correct Answer + Core Reason: Methyl isocyanate. The gas released during the Bhopal tragedy was methyl isocyanate (MIC).

Step-by-Step Solution:

Step 1: Recall the Bhopal Gas Tragedy: This was a major industrial disaster.

Step 2: Identify the gas released: The gas released was methyl isocyanate (MIC).

Step 3: Conclusion: Therefore, the gas released during the Bhopal tragedy was methyl isocyanate.

Why other options are wrong:
- Option A: This is the correct answer as the gas released was methyl isocyanate.
- Option B: Potassium isothiocyanate is a different chemical compound and was not involved in the Bhopal tragedy.
- Option C: Sodium isothiocyanate is a different chemical compound and was not involved in the Bhopal tragedy.
- Option D: Ethyl isothiocyanate is a different chemical compound and was not involved in the Bhopal tragedy.

Key Concepts:
- Industrial disasters
- Methyl isocyanate (MIC)
- Environmental pollution

Memory Aids:
- Remember \"MIC\" for Methyl Isocyanate and associate it with the Bhopal tragedy.

Quick Tips:
- Be familiar with major environmental disasters and the chemicals involved.

71 Medium

71 of 71

Remembering +4 | -1

Depletion of ozone layer by CFCs is mainly due to formation of

View answer and explanation

Correct option: B

Chlorine radicals

Option B (Chlorine radicals) is correct because CFCs release chlorine atoms under UV radiation, which catalyze the destruction of ozone.

Solution approach

Correct Answer + Core Reason: Chlorine radicals. CFCs release chlorine atoms that destroy ozone.

Step-by-Step Solution:

Step 1: CFCs (chlorofluorocarbons) are stable compounds that can reach the stratosphere.

Step 2: In the stratosphere, UV radiation breaks down CFCs, releasing chlorine atoms (radicals).

Step 3: Chlorine radicals catalyze the destruction of ozone ( $O_3$ ) by converting it to oxygen ( $O_2$ ).

Step 4: The reactions are:
$CFCl_3 \xrightarrow{UV} CFCl_2 + Cl$
$Cl + O_3 \rightarrow ClO + O_2$
$ClO + O \rightarrow Cl + O_2$

Why other options are wrong:
- Option A (Fluorine radicals): Fluorine radicals are also released, but chlorine radicals are more effective at ozone depletion.
- Option C (Free oxygen atoms (O)): Free oxygen atoms are involved in the ozone depletion cycle, but they are not the primary cause of ozone depletion by CFCs.
- Option D (Both (1) and (2)): While both chlorine and fluorine radicals are released, chlorine radicals are the major cause of ozone depletion.

Key Concepts:
- Ozone Depletion
- CFCs
- Free Radicals
- Catalysis

Memory Aids:
- Remember that chlorine from CFCs is the main culprit in ozone depletion.

Quick Tips:
- Know the mechanism of ozone depletion by CFCs.

Your Progress

Environmental chemistry practice · Medium

Continue Your Practice

Your practice