A liquid particle resulting from vapour condensation

ENVIRONMENTAL CHEMISTRY MCQs for JEE CHEMISTRY — Medium, Page 2

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Statement I: Chlorofluorocarbons are reactive and flammable organic molecules.

Statement II:

\mathrm{CO}_2

is the major contributor to global warming.

In the light of above statements, select the correct option.

View answer and explanation

Correct option: B

Statement I is false but statement II is true

Option B (Statement I is false but statement II is true) is correct because chlorofluorocarbons are unreactive and non-flammable, while carbon dioxide is a major contributor to global warming.

Solution approach

Correct Answer + Core Reason: Statement I is false but statement II is true. CFCs are unreactive, and CO2 is a major greenhouse gas.

Step-by-Step Solution:

Step 1: Evaluate Statement I: Chlorofluorocarbons are reactive and flammable organic molecules. This is FALSE. CFCs are known for their stability and non-flammability, which is why they were widely used as refrigerants and propellants.

Step 2: Evaluate Statement II: $\mathrm{CO}_2$ is the major contributor to global warming. This is TRUE. Carbon dioxide is a significant greenhouse gas and a major contributor to global warming.

Step 3: Therefore, Statement I is false, and Statement II is true.

Why other options are wrong:
- Option A (Statement I is true but statement II is false): Statement I is false, and Statement II is true.
- Option C (Both statement I and II are true): Statement I is false.
- Option D (Both statement I and II are false): Statement II is true.

Key Concepts:
- Chlorofluorocarbons (CFCs)
- Global Warming
- Greenhouse Gases
- Carbon Dioxide

Memory Aids:
- CFCs: Stable, Non-flammable
- CO2: Greenhouse Gas

Quick Tips:
- Remember the properties of CFCs and the role of CO2 in global warming.

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Which of the following statements about polar stratosphere
clouds (PSCs) is not correct?

View answer and explanation

Correct option: A

PSCs do not react with chlorine nitrate and

HCl

Option A (PSCs do not react with chlorine nitrate and

HCl

) is not correct because PSCs provide a surface for the reaction of chlorine nitrate and

HCl

to form

HOCl

and

Cl_2

, which are crucial in ozone depletion.

Solution approach

Correct Answer + Core Reason: PSCs do not react with chlorine nitrate and $HCl$ is incorrect because PSCs provide a surface for these reactions to occur.

Step-by-Step Solution:

Step 1: Understand the role of Polar Stratospheric Clouds (PSCs) in ozone depletion.

Step 2: Consider the reactions that occur on the surface of PSCs. PSCs provide a surface for the following reactions:
- $ClONO_2(g) + HCl(s) \rightarrow Cl_2(g) + HNO_3(s)$
- $ClONO_2(g) + H_2O(s) \rightarrow HOCl(g) + HNO_3(s)$

Step 3: Analyze the given statements.
- PSCs do not react with chlorine nitrate and $HCl$ : This is incorrect because PSCs facilitate these reactions.
- Type I clouds are formed at about $-77^\circ C$ and contain solid $HNO_3 \cdot 3H_2O$ : This is correct.
- Type II clouds are formed at about $-85^\circ C$ and contain some ice: This is correct.
- A tight whirlpool of wind called Polar Vortex is formed which surrounds Antarctica: This is correct.

Why other options are wrong:
- Option B: Type I clouds are formed at about $- 77^\circ C$ and contain solid $HN{O_3}$ . $3{H_2}O$ is correct.
- Option C: Type II clouds are formed at about $- 85^\circ C$ and contain some ice is correct.
- Option D: A tight whirlpool of wind called Polar Vortex is formed which surrounds Antarctica is correct.

Key Concepts:
- Polar Stratospheric Clouds (PSCs)
- Ozone depletion
- Reactions on PSCs

Memory Aids:
- PSCs facilitate reactions that lead to ozone depletion.

Quick Tips:
- Remember the role of PSCs in providing a surface for reactions involving chlorine compounds.

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Among the gases (a)-(e), the gases that cause greenhouse effect are:
a)

C{O_2}

b)

{H_2}O

c)

CFCs

d)

{O_2}

e)

{O_3}

View answer and explanation

Correct option: C

(a), (d), (c) and (E)

Option C ((a), (d), (c) and (E)) is correct because

CO_2

,

H_2O

, CFCs, and

O_3

are greenhouse gases that trap UV radiation and heat the Earth.

Solution approach

Correct Answer + Core Reason: (a), (d), (c) and (E). These gases trap UV radiation and cause the greenhouse effect.

Step-by-Step Solution:

Step 1: Identify greenhouse gases from the list.

Step 2: Recall that $CO_2$ , $H_2O$ , CFCs, and $O_3$ are well-known greenhouse gases.

Step 3: Determine that $O_2$ is not a greenhouse gas.

Step 4: Select the option that includes only greenhouse gases.

Why other options are wrong:
- Option A: Includes $O_2$ which is not a greenhouse gas.
- Option B: Only includes $CO_2$ and $O_2$ , missing other greenhouse gases.
- Option D: Includes $O_2$ which is not a greenhouse gas.

Key Concepts:
- Greenhouse effect
- Greenhouse gases

Memory Aids:
- Remember the common greenhouse gases: $CO_2$ , $H_2O$ , CFCs, $O_3$ .

Quick Tips:
- Familiarize yourself with the list of common greenhouse gases.

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Thermal power plants can lead to

View answer and explanation

Correct option: A

acid rain

Option A (acid rain) is correct because thermal power plants release sulfur and nitrogen oxides, which contribute to acid rain formation.

Solution approach

Correct Answer + Core Reason: acid rain. Thermal power plants release oxides of sulfur and nitrogen that lead to acid rain.

Step-by-Step Solution:

Step 1: Identify the source of pollution: Thermal power plants.

Step 2: Identify the pollutants released: Oxides of nitrogen (NOx) and sulfur (SOx).

Step 3: Explain the formation of acid rain: NOx and SOx react with water in the atmosphere to form nitric acid (HNO3) and sulfuric acid (H2SO4).
$4N{O_2} + {O_2} + 2{H_2}O \to 4HN{O_3}$
$S{O_2} + \frac{1}{2}{O_2} + {H_2}O \to {H_2}S{O_4}$

Step 4: Explain the effect of acid rain: Acid rain lowers the pH of rainwater, causing environmental damage.

Why other options are wrong:
- Option B: Blue baby syndrome is caused by nitrate contamination in drinking water, not directly by thermal power plants.
- Option C: Ozone layer depletion is primarily caused by chlorofluorocarbons (CFCs), not emissions from thermal power plants.
- Option D: Eutrophication is caused by excessive nutrients (phosphates and nitrates) in water bodies, not directly by thermal power plants, although NOx emissions can indirectly contribute.

Key Concepts:
- Air pollution
- Acid rain formation
- Environmental impact of power plants

Memory Aids:
- Remember that sulfur and nitrogen oxides lead to acid rain.

Quick Tips:
- Know the major pollutants from different sources and their environmental effects.

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The false statement among the followings :

View answer and explanation

Correct option: A

The average residence time of NO is one month

Option A (The average residence time of NO is one month) is false because the average residence time of NO in the atmosphere is much shorter, typically around 4 days.

Solution approach

Correct Answer + Core Reason: The average residence time of NO is one month. The residence time of NO is approximately 4 days.

Step-by-Step Solution:

Step 1: Recall the residence time of NO: The average residence time of NO in the atmosphere is about 4 days.

Step 2: Compare with the given statement: The statement says one month, which is incorrect.

Step 3: Conclude that the statement is false.

Why other options are wrong:
- Option B: Limestone does act as a sink for SOx.
- Option C: SOx can be removed from flue gases using citrate ions.
- Option D: Ammonia acts as a sink for NOx.

Key Concepts:
- Atmospheric pollution
- Residence time
- NOx and SOx

Memory Aids:
- NO residence time: Short (days)

Quick Tips:
- Remember the approximate residence times of common pollutants.

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The component of photochemical smog which causes irritation to nose and throat is

View answer and explanation

Correct option: C

NO

Option C (

NO

) is correct because Nitrogen oxides (NOx) are major components of photochemical smog and cause irritation to the nose and throat.

Solution approach

Correct Answer + Core Reason: $NO$ . Nitrogen oxides cause irritation in photochemical smog.

Step-by-Step Solution:
Step 1: Understand the composition of photochemical smog.
Step 2: Photochemical smog contains ozone, nitrogen oxides, and volatile organic compounds (VOCs).
Step 3: Nitrogen oxides, particularly NO2, are irritants and cause respiratory problems.

Why other options are wrong:
- Option A: Oxygen is not the primary irritant in photochemical smog.
- Option B: Carbon dioxide is a greenhouse gas but not a primary irritant in photochemical smog.
- Option C: Nitrogen oxides are the primary irritants in photochemical smog.
- Option D: Sulfur dioxide is a component of industrial smog, not photochemical smog.

Key Concepts:
- Photochemical smog
- Nitrogen oxides
- Air pollution

Memory Aids:
- Remember that nitrogen oxides are key components of photochemical smog and cause irritation.

Quick Tips:
- Differentiate between photochemical and industrial smog.

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Which is the resulting disease due to depletion of ozone layer.

View answer and explanation

Correct option: C

Skin cancer

Option C (Skin cancer) is correct because depletion of the ozone layer increases the amount of harmful UV radiation reaching the Earth's surface, which is a major cause of skin cancer.

Solution approach

Correct Answer + Core Reason: Skin cancer. Depletion of the ozone layer leads to increased UV radiation, causing skin cancer.

Step-by-Step Solution:

Step 1: Explain the role of the ozone layer: The ozone layer absorbs harmful UV radiation from the sun.

Step 2: Describe the effects of ozone depletion: Ozone depletion increases the amount of UV radiation reaching the Earth's surface.

Step 3: Relate UV radiation to health problems: Increased UV radiation exposure is a major cause of skin cancer.

Why other options are wrong:
- Option A: Thyroid cancer is not directly linked to ozone depletion.
- Option B: Pulmonary cancer is primarily linked to smoking and air pollution, not ozone depletion.
- Option D: Breast cancer is not directly linked to ozone depletion.

Key Concepts:
- Ozone layer
- UV radiation
- Skin cancer

Memory Aids:
- Ozone depletion -> Increased UV -> Skin cancer.

Quick Tips:
- Remember the link between ozone depletion and skin cancer.

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Smog is:

View answer and explanation

Correct option: B

A combination of smoke and fog

Option B (A combination of smoke and fog) is correct because smog is defined as a mixture of smoke and fog in the atmosphere.

Solution approach

Correct Answer + Core Reason: A combination of smoke and fog. Smog is a type of air pollution formed by the combination of smoke and fog.

Step-by-Step Solution:

Step 1: Smog is a portmanteau of the words smoke and fog.

Step 2: It is a type of air pollution that reduces visibility.

Step 3: It is often caused by the presence of particulate matter and ground-level ozone.

Why other options are wrong:
- Option A: Nothing but black smoke. While smoke is a component of smog, it's not the only component. Smog also includes fog and other pollutants.
- Option C: A liquid particle resulting from vapour condensation. This describes fog or mist, but not smog.
- Option D: A solid particle, e.g., flyash. Flyash can be a component of air pollution, but smog is a broader term encompassing smoke, fog, and other pollutants.

Key Concepts:
- Air Pollution
- Smog Formation

Memory Aids:
- Think of "sm" from smoke and "og" from fog to remember smog.

Quick Tips:
- Smog is a general term for air pollution, so look for answers that include multiple components.

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Choose the compound that always present in photochemical smog.

View answer and explanation

Correct option: A

\mathrm{O}_3

Option A (

\mathrm{O}_3

) is correct because ozone is always formed during the photochemical smog formation process due to the reaction of oxygen atoms with oxygen molecules.

Solution approach

Correct Answer + Core Reason: $\mathrm{O}_3$ . Ozone is a key component formed during photochemical smog.

Step-by-Step Solution:

Step 1: Understand the formation of photochemical smog. Photochemical smog is formed through a series of reactions involving nitrogen oxides, volatile organic compounds (VOCs), and sunlight.

Step 2: Identify the role of $\mathrm{NO}_2$ . Nitrogen dioxide ( $\mathrm{NO}_2$ ) absorbs sunlight and breaks down into nitric oxide ( $\mathrm{NO}$ ) and atomic oxygen (O).

Step 3: Explain the formation of ozone. The atomic oxygen (O) then reacts with molecular oxygen ( $\mathrm{O}_2$ ) to form ozone ( $\mathrm{O}_3$ ): $\mathrm{O} + \mathrm{O}_2 \rightarrow \mathrm{O}_3$

Step 4: Conclude that ozone is always present in photochemical smog because it is a direct product of these reactions.

Why other options are wrong:
- Option B: CO (Carbon monoxide) is a pollutant but not always present specifically in photochemical smog. It's more generally associated with incomplete combustion.
- Option C: $\mathrm{CO}_2$ (Carbon dioxide) is a greenhouse gas and a general air pollutant, but not a defining component of photochemical smog.
- Option D: CHO (Aldehydes) are formed in photochemical smog, but not always present in significant quantities compared to ozone.

Key Concepts:
- Photochemical smog formation
- Reactions of nitrogen oxides
- Ozone formation

Memory Aids:
- Remember that ozone is a key indicator of photochemical smog.

Quick Tips:
- Focus on the primary pollutants and their reaction products when identifying components of photochemical smog.

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Choose the compound that produce toxic effect.

View answer and explanation

Correct option: B

Carbon monoxide-

\mathrm{Hb}

The correct answer is B (Carbon monoxide-

Hb

) because carbon monoxide binds to hemoglobin with much greater affinity than oxygen, leading to a toxic effect by preventing oxygen transport.

Solution approach

Correct Answer + Core Reason: Carbon monoxide- $Hb$ . Carbon monoxide binds to hemoglobin more strongly than oxygen, causing toxicity.

Step-by-Step Solution:

Step 1: Explain the function of hemoglobin (Hb): Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the body's tissues.

Step 2: Explain the interaction of oxygen with Hb: Oxygen binds reversibly to the iron atom in hemoglobin.

Step 3: Explain the interaction of carbon monoxide with Hb: Carbon monoxide binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin.

Step 4: Explain the toxic effect of carbon monoxide: Carboxyhemoglobin prevents oxygen from binding to hemoglobin, leading to oxygen deprivation and toxicity.

Why other options are wrong:
- **Option A (Carbon dioxide- $Hb$ ): Carbon dioxide binds to hemoglobin, but not as strongly as carbon monoxide, and it is a normal part of respiration.
- Option C (Oxygen- $Hb$ ): Oxygen binding to hemoglobin is essential for life.
- Option D (Carbon suboxide- $Hb$ ): Carbon suboxide is less common and less well-known for its toxic effects compared to carbon monoxide.

Key Concepts:
- Hemoglobin
- Carbon monoxide poisoning
- Oxygen transport

Memory Aids:
- CO is a silent killer because it binds strongly to Hb.

Quick Tips:**
- Remember that carbon monoxide is a highly toxic gas due to its strong affinity for hemoglobin.

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Maximum prescribed concentration of

\mathrm{Fe}

in drinking water is

View answer and explanation

Correct option: A

0.2 \mathrm{~ppm}

Option A (0.2 ppm) is correct because the maximum prescribed concentration of iron (Fe) in drinking water is 0.2 ppm according to established guidelines.

Solution approach

Correct Answer + Core Reason: 0.2 ppm. The maximum permissible limit of iron in drinking water is 0.2 ppm.

Step-by-Step Solution:

Step 1: Recall the standard limits for contaminants in drinking water.

Step 2: Identify the permissible limit for iron (Fe). The prescribed concentration of Fe in drinking water is 0.2 ppm.

Why other options are wrong:
- Option B: 0.05 ppm is too low. The standard limit is higher than this.
- Option C: 3.0 ppm is too high. This concentration would be considered unsafe for drinking water.
- Option D: 0.005 ppm is also too low. The standard limit is higher than this.

Key Concepts:
- Water quality standards
- Permissible limits of contaminants

Memory Aids:
- Remember the common limits for drinking water contaminants.

Quick Tips:
- Refer to standard guidelines for water quality.

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Increased UV radiations due to hole in ozone layer

View answer and explanation

Correct option: A

Will cause increase in cases of skin diseases

Option A (Will cause increase in cases of skin diseases) is correct because increased UV radiation exposure is a known cause of skin diseases, including skin cancer.

Solution approach

Correct Answer + Core Reason: Will cause increase in cases of skin diseases. UV radiation is harmful and causes skin diseases.

Step-by-Step Solution:

Step 1: Identify the effect of increased UV radiation.

Step 2: UV radiation possesses high energy and is harmful to human life.

Step 3: UV radiation causes skin cancer, swelling of skin, sunburns, and burning sensations on the skin.

Why other options are wrong:
- Option B (Will cause more ice to melt): While UV radiation contributes to warming, it's not the primary driver of ice melting compared to other factors like greenhouse gases.
- Option C (Will cause summer to be more warmer): UV radiation contributes to warming, but it's not the only factor determining summer temperatures.
- Option D (Will cause more rain): UV radiation does not directly cause more rain.

Key Concepts:
- UV radiation
- Ozone layer depletion
- Health effects of UV radiation

Memory Aids:
- UV radiation is harmful to the skin.

Quick Tips:
- Remember the direct link between UV exposure and skin damage.

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Which of the following pollutants is not emitted during volcanic eruptions?

View answer and explanation

Correct option: D

Hydrocarbons

Option D (Hydrocarbons) is correct because volcanic eruptions primarily emit gases like sulfur dioxide, hydrogen sulfide, and carbon monoxide, but not significant amounts of hydrocarbons.

Solution approach

Correct Answer + Core Reason: Hydrocarbons are not emitted during volcanic eruptions.

Step-by-Step Solution:

Step 1: Identify the question: The question asks which pollutant is not emitted during volcanic eruptions.

Step 2: Recall the common pollutants emitted during volcanic eruptions.

Step 3: Volcanic eruptions emit gases like sulfur dioxide, hydrogen sulfide, and carbon monoxide.

Step 4: Hydrocarbons are not typically emitted during volcanic eruptions.

Why other options are wrong:
- Option A: $\mathrm{S}{\mathrm{O}_2}$ (Sulfur dioxide) is emitted during volcanic eruptions.
- Option B: ${\mathrm{H}_2}\mathrm{S}$ (Hydrogen sulfide) is emitted during volcanic eruptions.
- Option C: $CO$ (Carbon monoxide) is emitted during volcanic eruptions.

Key Concepts:
- Volcanic eruptions
- Air pollutants

Memory Aids:
- Volcanoes emit sulfur and carbon gases.

Quick Tips:
- Remember the common pollutants from volcanic eruptions.

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Sewage mostly constitutes:

View answer and explanation

Correct option: B

Biodegradable pollutants

Option B (Biodegradable pollutants) is correct because sewage primarily consists of organic waste that can be decomposed by microorganisms.

Solution approach

Correct Answer + Core Reason: Biodegradable pollutants. Sewage mainly consists of organic waste.

Step-by-Step Solution:

Step 1: Define sewage. Sewage is wastewater containing domestic, industrial, and agricultural waste.

Step 2: Identify the main components of sewage. The main components are organic matter, nutrients, and pathogens.

Step 3: Determine the nature of the pollutants. Most of the organic matter in sewage is biodegradable, meaning it can be decomposed by microorganisms.

Why other options are wrong:
- Option A: Non – biodegradable pollutants: While some non-biodegradable pollutants may be present, the majority of sewage consists of biodegradable material.
- Option C: Effluents: Effluents are the outflow of treated or untreated wastewater, which may contain various pollutants, but sewage itself is the raw wastewater.
- Option D: Air pollutants: Sewage primarily pollutes water, not air.

Key Concepts:
- Sewage
- Biodegradable pollutants
- Water pollution

Memory Aids:
- Sewage = organic waste = biodegradable.

Quick Tips:
- Sewage is a major source of water pollution due to its high organic content.

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Main pollutant from automobile exhaust is

View answer and explanation

Correct option: A

CO

Option A (

CO

) is correct because carbon monoxide is the primary pollutant released from automobile exhaust due to incomplete combustion.

Solution approach

Correct Answer + Core Reason: $CO$ . Carbon monoxide is the main pollutant from automobile exhaust due to incomplete combustion.

Step-by-Step Solution:

Step 1: Identify the source of pollution: Automobile exhaust.

Step 2: Recall the major pollutants released from automobile exhaust.

Step 3: Recognize that carbon monoxide ( $CO$ ) is a primary pollutant due to incomplete combustion of fuel in engines.

Step 4: Conclude that $CO$ is the main pollutant.

Why other options are wrong:
- **Option B ( $CO_2$ ):** Carbon dioxide is a greenhouse gas but not the main *pollutant* in the context of direct toxicity and air quality.
- **Option C ( $NO$ ):** Nitrogen oxides ( $NO_x$ ) are pollutants, but generally less abundant than $CO$ in automobile exhaust. They are secondary pollutants that form smog and acid rain.
- Option D (Hydrocarbons): Unburnt hydrocarbons are pollutants, but $CO$ is produced in larger quantities and is more directly harmful.

Key Concepts:
- Air pollution
- Automobile exhaust
- Incomplete combustion
- Carbon monoxide toxicity

Memory Aids:
- CO is a silent killer (relates to its toxicity).

Quick Tips:
- Remember that incomplete combustion leads to $CO$ formation.

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BOD is a measure of:

View answer and explanation

Correct option: A

Organic pollutant in water

Option A (Organic pollutant in water) is correct because BOD measures the amount of oxygen required to decompose organic matter in water.

Solution approach

Correct Answer + Core Reason: Organic pollutant in water. BOD measures the amount of oxygen needed to decompose organic material in water.

Step-by-Step Solution:

Step 1: Define BOD: Biochemical Oxygen Demand.

Step 2: BOD is a measure of the amount of oxygen required by microorganisms to decompose the organic matter in a water sample.

Step 3: Higher BOD indicates a higher level of organic pollution.

Why other options are wrong:
- Option B: Oxides of SPN are air pollutants, not directly related to BOD.
- Option C: BOD primarily measures organic pollutants, not inorganic pollutants.
- Option D: Particle matter is related to turbidity, not BOD.

Key Concepts:
- Biochemical Oxygen Demand (BOD)
- Water pollution
- Organic pollutants

Memory Aids:
- BOD = Biological Oxygen Demand, related to organic matter.

Quick Tips:
- BOD is a key indicator of water quality.

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SO_2

causes

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because

SO_2

contributes to respiratory issues, acid rain, and corrosion of building materials.

Solution approach

Correct Answer + Core Reason: All of the above is the correct answer because $SO_2$ causes respiratory problems, acid rain, and corrosion.

Step-by-Step Solution:

Step 1: Understand the effects of $SO_2$ pollution.

Step 2: $SO_2$ is a major air pollutant.

Step 3: $SO_2$ causes respiratory and lung diseases by irritating the respiratory tract.

Step 4: $SO_2$ contributes to acid rain by reacting with water in the atmosphere to form sulfuric acid.

Step 5: $SO_2$ corrodes building materials, especially those made of limestone and marble.

Why other options are wrong:
- Option A (Respiratory and lung disease): This is a correct effect of $SO_2$ , but not the only one.
- Option B (Acid rain): This is a correct effect of $SO_2$ , but not the only one.
- Option C (Corrosion of building materials): This is a correct effect of $SO_2$ , but not the only one.

Key Concepts:
- Air pollution
- Effects of $SO_2$
- Acid rain
- Corrosion

Memory Aids:
- Remember the multiple harmful effects of $SO_2$ .

Quick Tips:
- Consider all the environmental and health impacts of pollutants.

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London smog is found in:

View answer and explanation

Correct option: C

Winter during morning time

Option C (Winter during morning time) is correct because London smog, also known as classical smog, typically occurs during winter mornings due to coal combustion and temperature inversions.

Solution approach

Correct Answer + Core Reason: Winter during morning time. London smog is associated with cold, stagnant air conditions that trap pollutants.

Step-by-Step Solution:

Step 1: Define London smog (classical smog).

Step 2: Identify the primary pollutants: sulfur dioxide and particulate matter from coal combustion.

Step 3: Recall the meteorological conditions favorable for smog formation: cold temperatures, temperature inversions, and stagnant air.

Step 4: Relate these conditions to winter mornings when coal burning is high and inversions are common.

Why other options are wrong:
- Option A: Summer during day time: Summer conditions and daytime heat tend to disperse pollutants, not concentrate them into smog.
- Option B: Summer during morning time: Similar to option A, summer conditions are not conducive to London smog formation.
- Option D: Winter during day time: While winter is correct, daytime conditions may allow some dispersion of pollutants compared to the morning.

Key Concepts:
- Air pollution
- Smog formation (classical vs. photochemical)
- Temperature inversion

Memory Aids:
- London smog = Classical smog = Coal + Cold

Quick Tips:
- Differentiate between London smog (reducing smog) and photochemical smog (oxidizing smog).

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Which of the following is a sink for

\mathrm{CO}

?

View answer and explanation

Correct option: C

Micro-organisms present in the soil

Option C (Micro-organisms present in the soil) is correct because soil microorganisms can oxidize CO to CO2, effectively removing it from the atmosphere.

Solution approach

Correct Answer + Core Reason: Micro-organisms present in the soil. Soil microorganisms act as a sink for CO by oxidizing it to CO2.

Step-by-Step Solution:

Step 1: Understand the question: Identify the sink for carbon monoxide (CO).

Step 2: Define a sink: A sink is a reservoir that absorbs or removes a substance from the atmosphere.

Step 3: Consider the options:
- Plants: Primarily absorb $\mathrm{CO}_2$ during photosynthesis.
- Haemoglobin: Binds to CO in the blood, but doesn't remove it from the environment.
- Micro-organisms present in the soil: Some soil bacteria can oxidize CO to $\mathrm{CO}_2$ .
- Oceans: Absorb $\mathrm{CO}_2$ , not CO.

Step 4: Identify the correct sink: Soil microorganisms are known to consume CO.

Why other options are wrong:
- Option A: Plants primarily absorb carbon dioxide ( $\mathrm{CO}_2$ ) during photosynthesis, not carbon monoxide (CO).
- Option B: Haemoglobin binds to CO in the bloodstream, causing carbon monoxide poisoning. It does not act as a sink for CO in the environment.
- Option D: Oceans primarily absorb carbon dioxide ( $\mathrm{CO}_2$ ) from the atmosphere, not carbon monoxide (CO).

Key Concepts:
- Carbon Monoxide (CO)
- Carbon Dioxide ( $\mathrm{CO}_2$ )
- Environmental Sinks
- Soil Microorganisms

Memory Aids:
- Remember that soil bacteria play a crucial role in breaking down pollutants in the environment.

Quick Tips:
- Think about the natural processes that remove pollutants from the atmosphere when identifying sinks.

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In which of the following regions hydrogen and helium are
found?

View answer and explanation

Correct option: C

Exosphere

Option C (Exosphere) is correct because hydrogen and helium are the primary constituents of the exosphere, the outermost layer of the atmosphere.

Solution approach

Correct Answer + Core Reason: Exosphere. Hydrogen and helium are found in the exosphere.

Step-by-Step Solution:

Step 1: Recall the layers of the atmosphere: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.

Step 2: Consider the composition of each layer:
- Troposphere: Primarily nitrogen and oxygen.
- Stratosphere: Contains the ozone layer.
- Mesosphere: Coldest layer.
- Thermosphere: High temperature, but low density.
- Exosphere: Outermost layer, primarily hydrogen and helium.

Why other options are wrong:
- Option A (Stratosphere): The stratosphere contains the ozone layer and is primarily composed of nitrogen and oxygen.
- Option B (Mesosphere): The mesosphere is the coldest layer and does not have a significant amount of hydrogen and helium.
- Option D (Troposphere): The troposphere is the lowest layer and is primarily composed of nitrogen and oxygen.

Key Concepts:
- Atmospheric layers
- Atmospheric composition

Memory Aids:
- Remember that the exosphere is the outermost layer and is composed mainly of hydrogen and helium.

Quick Tips:
- Know the order and composition of the atmospheric layers.

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Photochemical smog does not contain

View answer and explanation

Correct option: B

S{O_2}

Option B (

S{O_2}

) is correct because photochemical smog is characterized by the presence of ozone, PAN, and nitrogen oxides, but not sulfur dioxide.

Solution approach

Correct Answer + Core Reason: $S{O_2}$ . Photochemical smog is characterized by oxidants like ozone and PAN, and nitrogen oxides, but not sulfur dioxide.

Step-by-Step Solution:

Step 1: Define photochemical smog.\nPhotochemical smog is a type of air pollution that occurs when sunlight reacts with nitrogen oxides and volatile organic compounds (VOCs) in the atmosphere.

Step 2: Identify the components of photochemical smog.\nThe main components of photochemical smog are:
- Ozone ( $O_3$ )
- Peroxyacyl nitrates (PANs)
- Nitrogen oxides ( $NO_x$ )
- Volatile organic compounds (VOCs)

Step 3: Explain the absence of sulfur dioxide.\nSulfur dioxide ( $SO_2$ ) is a component of classical smog, which is associated with industrial pollution and the burning of sulfur-containing fuels.\nPhotochemical smog is primarily formed from vehicle emissions and does not typically contain significant amounts of $SO_2$ .

Step 4: Final Answer\nPhotochemical smog does not contain $S{O_2}$ .

Why other options are wrong:
- Option A: ${O_3}$ is incorrect because ozone is a key component of photochemical smog.
- Option C: PAN is incorrect because PANs are formed in photochemical smog and are strong irritants.
- Option D: $N{O_x}$ is incorrect because nitrogen oxides are precursors to the formation of photochemical smog.

Key Concepts:
- Photochemical smog
- Components of photochemical smog
- Difference between photochemical and classical smog

Memory Aids:
- Remember that "Photochemical Smog = Ozone, PAN, NOx".

Quick Tips:
- Distinguish between the components of photochemical and classical smog.

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Chlorofluorocarbons (CFCs) are widely used in air conditioners, refrigerators etc because of being

View answer and explanation

Correct option: C

Non reactive

Option C (Non reactive) is correct because Chlorofluorocarbons (CFCs) are widely used due to their non-reactive, non-flammable, and non-toxic properties.

Solution approach

Correct Answer + Core Reason: Non reactive. CFCs are used because they are non-reactive.

Step-by-Step Solution:
Step 1: Recall the properties of CFCs.
Step 2: Chlorofluorocarbons (CFCs) are widely used in air conditioners and refrigerators because they are non-reactive, non-flammable, and non-toxic.
Step 3: Their non-reactivity makes them stable and suitable for these applications.

Why other options are wrong:
- Option A: CFCs are not highly reactive; in fact, their low reactivity is a key reason for their use.
- Option B: CFCs are non-flammable, not flammable.
- Option D: While they are non-flammable and non-reactive, the best answer is C because it directly addresses the reason for their use.

Key Concepts:
- Chlorofluorocarbons (CFCs)
- Properties of CFCs

Memory Aids:
- CFCs are stable and non-reactive.

Quick Tips:
- Remember the key properties that make CFCs useful.

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Assertion: London smog is oxidising in nature.
Reason: London smog contains

{O}_3, {NO}_2

and hydrocabons.

View answer and explanation

Correct option: D

Both Assertion and Reason are false

Option D (Both Assertion and Reason are false) is correct because London smog is reducing in nature and does not primarily contain

O_3

,

NO_2

, and hydrocarbons.

Solution approach

Correct Answer + Core Reason: Both Assertion and Reason are false. London smog is reducing and contains sulfur oxides, not primarily ozone and nitrogen dioxide.

Step-by-Step Solution:
Step 1: London smog, also known as classical smog, is characterized by reducing conditions due to the presence of sulfur dioxide and particulate matter.
Step 2: The primary components of London smog are sulfur oxides and smoke, not ozone, nitrogen dioxide, and hydrocarbons.
Step 3: Therefore, the assertion that London smog is oxidizing is false, and the reason that it contains ozone, nitrogen dioxide, and hydrocarbons is also false.

Why other options are wrong:
- Option A: Both assertion and reason are true and Reason is the correct explanation of Assertion: Both are false.
- Option B: Both assertion and reason are true but Reason is not the correct explanation of Assertion: Both are false.
- Option C: Assertion is true but Reason is false: Assertion is false.

Key Concepts:
- London smog (classical smog)
- Reducing smog
- Air pollution

Memory Aids:
- London smog: Sulfur oxides and smoke
- Photochemical smog: Ozone and nitrogen oxides

Quick Tips:
- Differentiate between London smog (reducing) and photochemical smog (oxidizing).

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Bio-degradable pollutant pair is

View answer and explanation

Correct option: A

Domestic waste and sewage

Option A (Domestic waste and sewage) is correct because domestic waste and sewage are organic materials that can be decomposed by microorganisms, making them biodegradable pollutants.

Solution approach

Correct Answer + Core Reason: Domestic waste and sewage. These are biodegradable pollutants.

Step-by-Step Solution:

Step 1: Define biodegradable pollutants.

Step 2: Biodegradable pollutants are substances that can be decomposed by microorganisms into harmless products.

Step 3: Domestic waste and sewage consist of organic materials that can be broken down by bacteria and other microorganisms.

Why other options are wrong:
- Option B: DDT and Mercury salt. DDT and mercury salts are non-biodegradable and persist in the environment.
- Option C: Mercury salt and plastic. Mercury salt and plastic are non-biodegradable and persist in the environment.
- Option D: Aluminium foil and DDT. Aluminium foil and DDT are non-biodegradable and persist in the environment.

Key Concepts:
- Biodegradable pollutants
- Non-biodegradable pollutants
- Environmental pollution

Memory Aids:
- Biodegradable: Decomposed by microorganisms

Quick Tips:
- Remember the difference between biodegradable and non-biodegradable pollutants.

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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)

\mathrm{Smog}

View answer and explanation

Correct option: C

Only (ii)

Option C (Only (ii)) is correct because the irritant red haze in traffic and congested areas is primarily due to the presence of oxides of nitrogen.

Solution approach

Correct Answer + Core Reason: Only (ii). Oxides of nitrogen are the primary cause of the irritant red haze.

Step-by-Step Solution:

Step 1: Identify the common air pollutants.

Step 2: Recall the sources and effects of each pollutant:
- Oxides of sulphur: Cause respiratory problems and acid rain.
- Oxides of nitrogen: Cause respiratory problems and contribute to smog and haze.
- Carbon dioxide: Greenhouse gas.
- Mists, smoke and dust: Reduce visibility and cause respiratory problems.
- Smog: A mixture of pollutants, including oxides of nitrogen.

Step 3: The irritant red haze is primarily caused by $NO_2$ , which is a reddish-brown gas.

Why other options are wrong:
- Option A: (i), (iv) and (v) - While these can contribute to air pollution, they are not the primary cause of the red haze.
- Option B: Only (iii) - Carbon dioxide is not responsible for the red haze.
- Option D: (ii) and (v) - While smog contains oxides of nitrogen, the oxides of nitrogen themselves are the direct cause of the haze.

Key Concepts:
- Air pollution
- Oxides of nitrogen
- Smog

Memory Aids:
- $NO_2$ is a reddish-brown gas.

Quick Tips:
- Remember the common air pollutants and their sources.

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Ozone has the ability to absorb

View answer and explanation

Correct option: A

UV radiations

Option A (UV radiations) is correct because the ozone layer absorbs harmful ultraviolet (UV) radiations from the sun.

Solution approach

Correct Answer + Core Reason: UV radiations. Ozone absorbs UV radiations.

Step-by-Step Solution:

Step 1: Recall the role of the ozone layer in the stratosphere.

Step 2: Identify the type of radiation absorbed by the ozone layer. The ozone layer absorbs harmful ultraviolet (UV) radiations from the sun.

Step 3: Conclude that ozone has the ability to absorb UV radiations.

Why other options are wrong:
- Option B: Ozone does not primarily absorb electromagnetic radiations in general, but specifically UV radiations.
- Option C: CFCs (chlorofluorocarbons) are substances that deplete the ozone layer, not absorbed by it.
- Option D: Greenhouse gases trap heat in the atmosphere, but they are not directly absorbed by ozone.

Key Concepts:
- Ozone layer
- UV radiation
- Role of ozone in the stratosphere

Memory Aids:
- Ozone protects us from the sun's harmful UV rays.

Quick Tips:
- Remember that the ozone layer is crucial for absorbing UV radiation and protecting life on Earth.

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Identify the wrong statement in the following

View answer and explanation

Correct option: D

Ozone layer does not permit infrared radiation from the sun to reach the earth

Option D (Ozone layer does not permit infrared radiation from the sun to reach the earth) is the wrong statement because the ozone layer primarily blocks ultraviolet (UV) radiation, not infrared radiation.

Solution approach

Correct Answer + Core Reason: Ozone layer does not permit infrared radiation from the sun to reach the earth. Ozone layer primarily blocks UV radiation, not infrared radiation.

Step-by-Step Solution:

Step 1: Recall the role of the ozone layer in the atmosphere.

Step 2: Analyze each statement:
- A: Chlorofluorocarbons deplete the ozone layer (correct).
- B: Acid rain is caused by oxides of nitrogen and sulfur (correct).
- C: Greenhouse effect causes global warming (correct).
- D: Ozone layer blocks infrared radiation (incorrect).

Step 3: Identify the incorrect statement: Statement D.

Why other options are wrong:
- Option A: Chlorofluorocarbons (CFCs) are well-known for their role in ozone depletion. This statement is correct.
- Option B: Oxides of nitrogen and sulfur are major contributors to acid rain. This statement is correct.
- Option C: The greenhouse effect, caused by gases like CO2, is a primary driver of global warming. This statement is correct.

Key Concepts:
- Ozone Layer
- Chlorofluorocarbons (CFCs)
- Acid Rain
- Greenhouse Effect
- Global Warming

Memory Aids:
- Ozone layer protects from UV radiation.

Quick Tips:
- Remember the specific types of radiation blocked by the ozone layer.

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Which compound is not included under pollutant?

View answer and explanation

Correct option: B

\mathrm{CO}_2

Option B (

\mathrm{CO}_2

) is correct because carbon dioxide is a natural component of the atmosphere and is not considered a pollutant at normal concentrations.

Solution approach

Correct Answer + Core Reason: $\mathrm{CO}_2$ . Carbon dioxide is not considered a pollutant at normal atmospheric concentrations.

Step-by-Step Solution:

Step 1: Define pollutants. Pollutants are substances that contaminate the environment and cause adverse effects on living organisms and ecosystems.

Step 2: Evaluate each option:
- $\mathrm{NO}_2$ : Nitrogen dioxide is a pollutant that contributes to smog and acid rain.
- $\mathrm{CO}_2$ : Carbon dioxide is a greenhouse gas, but it is a natural component of the atmosphere. While elevated levels contribute to climate change, normal concentrations are not considered pollutants.
- $\mathrm{O}_3$ : Ozone is a pollutant in the troposphere (ground level), contributing to smog. In the stratosphere, it is beneficial as it absorbs UV radiation.
- $\mathrm{C}_{\mathrm{X}} \mathrm{H}_{\mathrm{y}}$ : Hydrocarbons can be pollutants, contributing to smog and other environmental problems.

Step 3: Identify the compound not typically considered a pollutant at normal concentrations. Carbon dioxide is the correct answer.

Why other options are wrong:
- **Option A ( $\mathrm{NO}_2$ ): Nitrogen dioxide is a pollutant.
- Option C ( $\mathrm{O}_3$ ): Ozone is a pollutant at ground level.
- Option D ( $\mathrm{C}_{\mathrm{X}} \mathrm{H}_{\mathrm{y}}$ ): Hydrocarbons are pollutants.

Key Concepts:
- Air pollution
- Greenhouse gases
- Environmental chemistry

Memory Aids:**
- $\mathrm{CO}_2$ is a natural atmospheric component.

Quick Tips:
- Differentiate between natural atmospheric components and pollutants.

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Lead pollution is mainly caused by

View answer and explanation

Correct option: C

Coal gasoline

Option C (Coal gasoline) is correct because leaded gasoline was a major source of lead pollution due to the use of tetraethyllead as an antiknock agent.

Solution approach

Correct Answer + Core Reason: Coal gasoline. Lead pollution is mainly caused by coal gasoline due to the addition of lead compounds.

Step-by-Step Solution:

Step 1: Identify the sources of lead pollution. Common sources include leaded gasoline, industrial processes (e.g., smelting), and lead-based paints.

Step 2: Explain the role of leaded gasoline. Tetraethyllead (TEL) was added to gasoline as an antiknock agent to improve engine performance. However, the combustion of leaded gasoline released lead into the atmosphere, causing widespread pollution.

Step 3: Relate coal gasoline to lead pollution. Coal gasoline refers to gasoline produced from coal, which historically contained lead additives.

Why other options are wrong:
- Option A (Sewage): Sewage can contain various pollutants, but it is not a primary source of lead pollution.
- Option B (Insecticide): Some insecticides may contain heavy metals, but they are not the main cause of lead pollution compared to leaded gasoline.
- Option D (None of these): Coal gasoline is a significant source of lead pollution.

Key Concepts:
- Lead pollution
- Sources of pollution
- Antiknock agents

Memory Aids:
- Leaded gasoline = Lead pollution

Quick Tips:
- Remember the historical use of leaded gasoline as a major source of lead pollution.

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Which of the following is the hottest region of the atmosphere?

View answer and explanation

Correct option: C

Thermosphere

Option C (Thermosphere) is correct because the thermosphere absorbs high-energy radiation from the sun, causing it to heat up significantly.

Solution approach

Correct Answer + Core Reason: Thermosphere. The thermosphere absorbs high energy radiation from the sun.

Step-by-Step Solution:

Step 1: Define the layers of the atmosphere.

Step 2: Troposphere: The lowest layer, where weather occurs.

Step 3: Stratosphere: Contains the ozone layer.

Step 4: Mesosphere: The middle layer.

Step 5: Thermosphere: The outermost layer, absorbs high-energy radiation from the sun, causing it to heat up significantly.

Why other options are wrong:
- Option A: Mesosphere is incorrect. The mesosphere is colder than the thermosphere.
- Option B: Stratosphere is incorrect. The stratosphere is also colder than the thermosphere.
- Option D: Troposphere is incorrect. The troposphere is the coolest layer overall.

Key Concepts:
- Atmospheric layers
- Temperature profiles of the atmosphere

Memory Aids:
- Remember the order of the atmospheric layers and their temperature characteristics.

Quick Tips:
- Know the basic properties of each atmospheric layer.

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