Samacheer Kalvi Class 11 Chemistry Solutions Chapter 15 Environmental Chemistry

Textbook Evaluation:

I. Choose the best answer:

 

Question 1. The gaseous envelope around the earth is known as atmosphere. The region lying between an altitudes of 11-50 km is
(a) Troposphere
(b) Mesosphere
(c) Thermosphere
(d) Stratosphere
Answer: (d) Stratosphere
In simple words: The atmosphere is divided into layers, and the stratosphere is the layer that sits above the troposphere, extending from about 11 km to 50 km above Earth's surface. This layer is important because it contains the ozone layer.

🎯 Exam Tip: Remember the order of atmospheric layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere. Each has distinct characteristics.

 

Question 2. Which of the following belongs to secondary air pollutant?
(a) Hydrocarbon
(b) Peroxy acetyl nitrate
(c) Carbon monoxide
(d) Nitric oxide
Answer: (b) Peroxy acetyl nitrate
In simple words: Secondary pollutants are not released directly into the air but form when other pollutants react in the atmosphere. Peroxy acetyl nitrate (PAN) is a good example of this, formed from reactions involving hydrocarbons and nitrogen oxides.

🎯 Exam Tip: Distinguish between primary pollutants (emitted directly, like CO, NO, SO2) and secondary pollutants (formed in the atmosphere, like ozone, PAN, acid rain).

 

Question 3. Which of the following is natural and human disturbance in ecology?
(a) Forest fire
(b) Floods
(c) Acid rain
(d) Green house effect
Answer: (b) Floods
In simple words: Floods can happen naturally, like from heavy rainfall, but human activities such as building on floodplains or deforestation can make them worse and more frequent. This shows how both nature and people can cause them.

🎯 Exam Tip: Think about environmental issues that can be triggered by natural events but intensified by human actions, such as floods, landslides, and droughts.

 

Question 4. Bhopal Gas Tragedy is a case of
(a) thermal pollution
(b) air pollution
(c) nuclear pollution
(d) land pollution
Answer: (b) air pollution
In simple words: The Bhopal Gas Tragedy involved the release of toxic gas into the air, which is a clear example of air pollution causing a major disaster. The gas quickly spread through the atmosphere, affecting many people.

🎯 Exam Tip: Recognize historical environmental disasters and classify them by the type of pollution involved (e.g., air, water, land, nuclear).

 

Question 5. Haemoglobin of the blood forms carboxy haemoglobin with
(a) Carbon dioxide
(b) Carbon tetra chloride
(c) Carbon monoxide
(d) Carbonic acid
Answer: (c) Carbon monoxide
In simple words: When carbon monoxide enters the body, it quickly attaches to haemoglobin in the blood, creating carboxyhaemoglobin. This is dangerous because it stops red blood cells from carrying oxygen properly to the body's tissues.

🎯 Exam Tip: Understand the specific interaction of carbon monoxide with haemoglobin, which is significantly stronger than oxygen's binding, leading to oxygen deprivation.

 

Question 6. Which sequence for green house gases is based on GWP?
(a) CFC > N2O > CO2 > CH4
(b) CFC > CO2 > N2O > CH4
(c) CFC > N2O > CH4 > CO2
(d) CFC > CH4 > N2O > CO2
Answer: (b) CFC > CO2 > N2O > CH4
In simple words: GWP stands for Global Warming Potential, which shows how much heat a greenhouse gas traps in the atmosphere compared to carbon dioxide. Chlorofluorocarbons (CFCs) have the highest GWP among these, making them very powerful warming agents, even more than carbon dioxide itself.

🎯 Exam Tip: Learn the relative global warming potentials of common greenhouse gases; CFCs are potent, followed by CO2, N2O, and CH4, though CO2 is often discussed most due to its sheer volume.

 

Question 7. Photochemical smog formed in congested metropolitan cities mainly consists of
(a) Ozone, SO2 and hydrocarbons
(b) Ozone, PAN and NO2
(c) PAN, smoke and SO2
(d) Hydrocarbons, SO2 and CO2
Answer: (b) Ozone, PAN and NO2
In simple words: Photochemical smog is a hazy air pollution that forms when sunlight reacts with certain chemicals, mainly nitrogen oxides (NO2) and volatile organic compounds (hydrocarbons), to produce new pollutants like ozone and peroxyacetyl nitrate (PAN). These are characteristic components in sunny urban areas.

🎯 Exam Tip: Differentiate between classical smog (sulfurous smog, typically from coal burning) and photochemical smog (oxidizing smog, from vehicle emissions in sunlight).

 

Question 8. The pH of normal rain water is
(a) 6.5
(b) 7.5
(c) 5.6
(d) 4.6
Answer: (c) 5.6
In simple words: Normal rainwater is naturally slightly acidic, not completely neutral, because it absorbs carbon dioxide from the air to form carbonic acid. This process typically gives it a pH of around 5.6.

🎯 Exam Tip: Remember that "normal" rainwater is slightly acidic due to dissolved CO2, while "acid rain" has a much lower pH, usually below 5.0, caused by other pollutants like SOx and NOx.

 

Question 9. Ozone depletion will cause
(a) forest fires
(b) eutrophication
(c) bio magnification
(d) global warming
Answer: (d) global warming
In simple words: While ozone depletion mainly leads to increased UV radiation on Earth's surface, the chemicals that cause ozone depletion, like CFCs, are also very strong greenhouse gases. So, ozone depletion contributes indirectly to global warming by releasing these heat-trapping substances.

🎯 Exam Tip: Understand the direct effects of ozone depletion (increased UV radiation, skin cancer) and its indirect link to global warming through shared pollutant classes (e.g., CFCs).

 

Question 10. ______ is considered to be ozone friendly substitude for CFC'S
(a) HFC (Hydro Fluro Carbon)
(b) Halons
(c) PAN (Peroxy acetyl nitrate)
(d) PAH (Poly cyclic aromatic hydro carbon)
Answer: (a) HFC (Hydro Fluro Carbon)
In simple words: Hydrofluorocarbons (HFCs) are used instead of CFCs because they do not contain chlorine, which is the main chemical that harms the ozone layer. However, HFCs are still potent greenhouse gases, so they are not a perfect solution.

🎯 Exam Tip: Be aware that while HFCs are ozone-friendly, they still contribute to global warming and are being phased out in favor of even more environmentally benign alternatives.

 

Question 11. Identify the wrong statement in the following.
(a) The clean water would have a BOD value of less than 5 ppm
(b) Greenhouse effect is also called as Global warming
(c) Minute solid particles in air is known as particulate pollutants
(d) Biosphere is the protective blanket of gases surrounding the earth
Answer: (d) Biosphere is the protective blanket of gases surrounding the earth
In simple words: The statement is wrong because the atmosphere, not the biosphere, is the protective blanket of gases around the Earth. The biosphere includes all living things and the parts of Earth where life exists, like land, water, and air.

🎯 Exam Tip: Clearly define key environmental terms like atmosphere, biosphere, lithosphere, and hydrosphere to avoid confusion.

 

Question 12. Living in the atmosphere of CO is dangerous because it
(a) combines with O2 present inside to form CO2
(b) Reduces organic matter of tissues
(c) Combines with haemoglobin and makes it incapable to absorb oxygen
(d) Dries up the blood
Answer: (c) Combines with haemoglobin and makes it incapable to absorb oxygen
In simple words: Carbon monoxide is very harmful because it binds to haemoglobin in our blood much more strongly than oxygen does. This means our blood cannot carry enough oxygen to our body, which can be deadly.

🎯 Exam Tip: Focus on the specific physiological mechanism of carbon monoxide poisoning, which is its strong affinity for haemoglobin.

 

Question 13. World Ozone layer protection Day is celebrated in
(a) June 5
(b) Nov - 19
(c) Sep - 16
(d) Jan - 26
Answer: (c) Sep - 16
In simple words: Every year on September 16, the world celebrates Ozone Day to remind everyone about the importance of protecting the Earth's ozone layer. This day marks when the Montreal Protocol, an important agreement to protect the ozone layer, was signed.

🎯 Exam Tip: Memorize important environmental dates like World Environment Day (June 5) and World Ozone Day (September 16).

 

Question 14. Release of oxides of nitrogen and hydrocarbons into the atmosphere by motor vehicles is prevented by using
(a) grit chamber
(b) scrubbers
(c) trickling filters
(d) catalytic convertors
Answer: (d) catalytic convertors
In simple words: Catalytic converters are devices in car exhaust systems that help clean up harmful gases like nitrogen oxides and hydrocarbons. They turn these bad gases into less harmful ones, like nitrogen, carbon dioxide, and water vapor, before they enter the air.

🎯 Exam Tip: Understand the function of catalytic converters in reducing vehicular emissions, specifically targeting NOx, CO, and unburnt hydrocarbons.

 

Question 15. Biochemical oxygen Demand value less than 5 ppm indicates a water sample to be
(a) highly polluted
(b) poor in dissolved oxygen
(c) rich in dissolved oxygen
(d) low COD
Answer: (c) rich in dissolved oxygen
In simple words: A low Biochemical Oxygen Demand (BOD) value, specifically less than 5 ppm, means that the water has very little organic pollution. This also means that there is a good amount of dissolved oxygen available for aquatic life to breathe.

🎯 Exam Tip: Associate low BOD values with clean water and good dissolved oxygen levels, indicating less organic pollution and healthier aquatic ecosystems.

 

Question 16. Match the List I with List II and select the correct answer using the code given below the lists:

Code:
a 3 4 1 2
b 2 1 4 3
c 4 3 2 1
d 2 4 1 3
Answer: (a)
In simple words: Matching the items: ozone layer depletion is linked to CFCs, acid rain is caused by SO2, photochemical smog involves NO, and the greenhouse effect is related to CO2. This shows how different pollutants affect specific environmental problems.

🎯 Exam Tip: When matching, link each environmental problem to its primary pollutant. CFCs deplete ozone, SO2 causes acid rain, NO forms photochemical smog, and CO2 contributes to the greenhouse effect.

 

Question 17. Match the List I with List II and select the correct answer using the code given below the lists.

Code:
a 3 4 1 2
b 2 1 4 3
c 4 3 2 1
d 2 4 1 3
Answer: (d)
In simple words: This matching exercise connects environmental problems to their causes. Stone leprosy (damage to stone) is caused by acid rain. Biological magnification refers to how toxins like DDT build up in a food chain. Global warming is caused by greenhouse gases. Carbon monoxide (CO) combines with haemoglobin in blood, which is a major health hazard.

🎯 Exam Tip: Understand the specific agents and processes for each environmental phenomenon. For example, acid rain's effect on stone, DDT's impact through food chains, and CO's direct interaction with blood.

 

Question 18. Assertion (A): If BOD level of water in a reservoir is more than 5 ppm it is highly polluted. Reason (R): High biological oxygen demand means high activity of bacteria in water.
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
Answer: (a) i
In simple words: The assertion is true because a BOD over 5 ppm indicates significant organic pollution. The reason is also true and explains why: more organic matter leads to more bacteria using up oxygen, which raises the BOD level and signifies polluted water.

🎯 Exam Tip: For assertion-reason questions, first determine if each statement is true. Then, check if the reason correctly explains the assertion. A high BOD indicates high pollution due to bacterial decomposition.

 

Question 19. Assertion (A): Excessive use of chlorinated pesticide causes soil and water pollution. Reason (R): Such pesticides are non-biodegradable.
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
Answer: (a) i
In simple words: The assertion is correct: too much use of chlorinated pesticides pollutes soil and water. The reason is also correct and explains why this happens: these pesticides do not break down easily in nature, so they stay in the environment for a long time.

🎯 Exam Tip: Understanding the non-biodegradable nature of many persistent organic pollutants (POPs) like chlorinated pesticides is key to explaining their long-term environmental impact.

 

Question 20. Assertion (A): Oxygen plays a key role in the troposphere Reason (R): Troposphere is not responsible for all biological activities
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
Answer: (b) ii
In simple words: The assertion is true because oxygen is crucial for life, and most biological activities occur in the troposphere where oxygen is abundant. The reason is also true, as not *all* biological activities are restricted to the troposphere (some specialized life forms exist elsewhere), but it doesn't explain *why* oxygen is key in the troposphere.

🎯 Exam Tip: While both statements might be true, ensure the reason directly explains the assertion. The troposphere contains the oxygen vital for most life, but saying it's "not responsible for all biological activities" doesn't explain oxygen's role.

II. Write brief answer to the following questions:

 

Question 21. Dissolved oxygen in water is responsible for aquatic life. What processes are responsible for the reduction in dissolved oxygen in water?
Answer: Several processes reduce dissolved oxygen in water. These include the overuse of phosphate and nitrate fertilizers, detergents, and the discharge of human sewage and organic waste from industries like food, paper, and pulp. Microorganisms also use oxygen to break down organic matter in water. Additionally, at night, aquatic plants continue to breathe but stop making oxygen through photosynthesis, further lowering oxygen levels. Water temperature also affects dissolved oxygen; warmer water holds less oxygen.
In simple words: Too much fertilizer, sewage, and industrial waste in water causes germs to grow, which use up oxygen. Also, at night, plants stop making oxygen, so fish and other water animals have less to breathe.

🎯 Exam Tip: When discussing dissolved oxygen reduction, remember the key factors: organic pollution (leading to microbial activity), nutrient loading (eutrophication), and temperature changes. These are critical for aquatic health.

 

Question 22. What would happen, if the greenhouse gases were totally missing in the earth's atmosphere?
Answer: If greenhouse gases were completely absent from Earth's atmosphere, the planet's average surface temperature would drop drastically to about -18°C. This is because there would be no gases to trap the solar energy radiated back from the Earth's surface. The greenhouse effect is a natural process that keeps our planet warm enough for life to exist. Without it, plant and animal life would not be able to survive on the surface of the Earth.
In simple words: Without greenhouse gases, the Earth would become extremely cold, too cold for any plants or animals to live. These gases act like a blanket, keeping our planet warm.

🎯 Exam Tip: Explain that the natural greenhouse effect is essential for life, not inherently bad. It only becomes a problem when human activities increase greenhouse gas concentrations too much.

 

Question 23. Define smog.
Answer: Smog is a type of air pollution made of smoke and fog, creating a yellowish-brown haze in the air, especially over cities. It's a mix of gases like ground-level ozone, nitrogen oxides, volatile organic compounds, and tiny solid particles. Smog can make it hard to breathe and see clearly. It forms from reactions involving pollutants released by human activities and sunlight.
In simple words: Smog is a thick, dirty haze in the air, made from smoke and fog. It also contains harmful gases and tiny particles, making it hard to breathe and see.

🎯 Exam Tip: Distinguish between the two main types: classical (sulfurous) smog, and photochemical smog (which involves sunlight and vehicle emissions).

 

Question 24. Which is considered to be earth's protective umbrella? Why?
Answer: The ozone layer, found high up in the atmosphere, is considered Earth's protective umbrella. It acts like a shield by absorbing most of the harmful ultraviolet (UV) radiation from the sun. This protection is vital because too much UV radiation can cause skin cancer, eye damage, and harm to plants. The ozone layer is constantly being formed and broken down by natural processes involving molecular oxygen, as shown in the reactions below:
\( \text{O}_2(g) \xrightarrow{\text{UV}} \text{O}(g) + \text{O}(g) \)
\( \text{O}(g) + \text{O}_2(g) \xrightarrow{\text{UV}} \text{O}_3(g) \)
In simple words: The ozone layer is like a giant umbrella high in the sky. It stops bad sunlight rays from reaching us and causing harm, like skin cancer.

🎯 Exam Tip: Clearly state that the ozone layer (O3) protects against UV radiation, and mention the harmful effects of increased UV exposure, such as skin cancer.

 

Question 25. What are degradable and non-degradable pollutants?
Answer: Pollutants are generally grouped into two types: bio-degradable and non-biodegradable. Bio-degradable pollutants are substances that can be easily broken down by natural biological processes, such as bacteria and fungi, into simpler, less harmful substances. Examples include plant and animal wastes. Non-biodegradable pollutants are substances that cannot be broken down by natural biological processes or break down very slowly. These harmful substances can stay in the environment for a very long time, accumulating and causing long-term damage. Examples include metal wastes (like mercury and lead), DDT, plastics, and nuclear wastes.
In simple words: Degradable pollutants can break down naturally, like food scraps. Non-degradable pollutants, like plastics or heavy metals, stay in nature for a very long time and don't break down easily.

🎯 Exam Tip: Give clear examples for both degradable (organic waste, paper) and non-degradable (plastics, heavy metals, DDT) pollutants to demonstrate understanding.

 

Question 26. From where does ozone come in the photo chemical smog?
Answer: In photochemical smog, ozone is not directly released but forms from chemical reactions in the air, especially in sunlight. Nitrogen dioxide (NO2) breaks down when exposed to sunlight, releasing nitric oxide (NO) and an oxygen atom. This free oxygen atom then reacts with molecular oxygen (O2) to form ozone (O3). Ozone is a powerful oxidizing agent and can react with unburnt hydrocarbons in polluted air to create other harmful chemicals like formaldehyde, acrolein, and peroxy acetyl nitrate (PAN). This process makes photochemical smog very toxic.
\( \text{NO}_2 \xrightarrow{\text{Sun light}} \text{NO} + \text{O} \)
\( \text{O} + \text{O}_2 \rightarrow \text{O}_3 \)
In simple words: Ozone in photochemical smog is made when sunlight hits nitrogen dioxide from car exhaust. This reaction creates single oxygen atoms that then combine with regular oxygen to form ozone, a key part of smog.

🎯 Exam Tip: Highlight that ozone in photochemical smog is a secondary pollutant, formed through a series of reactions initiated by sunlight, differentiating it from the beneficial stratospheric ozone.

 

Question 27. A person was using water supplied by corporation. Due to shortage of water he started using underground water. He felt laxative effect. What could be the cause?
Answer: The laxative effect experienced by the person suggests that the underground water they started using likely contained an excessive concentration of sulphate ions. While a moderate amount of sulphate is harmless, concentrations above 500 ppm in water are known to cause laxative effects. This indicates that the underground water source had higher levels of dissolved sulphates compared to the corporation-supplied water.
In simple words: The underground water probably had too much sulphate. When there is a lot of sulphate in water, it can act like a laxative and upset the stomach.

🎯 Exam Tip: Connect specific water contaminants to their health effects. Sulphates are a common cause of laxative effects at high concentrations, while other contaminants like nitrates or heavy metals have different impacts.

 

Question 28. What is green chemistry?
Answer: Green chemistry is a scientific field focused on designing chemical products and processes that reduce or eliminate the use and generation of hazardous substances. It aims to prevent pollution at its source rather than treating it after it has occurred. This approach involves finding environmentally friendly ways to make chemicals and conduct reactions, making them safer for both people and the planet.
In simple words: Green chemistry is about making chemicals and chemical processes that are safe and don't harm the environment. It tries to stop pollution before it even starts.

🎯 Exam Tip: Emphasize the core principle of green chemistry: "preventing pollution at the source." Mentioning the use of safer solvents and waste reduction are good examples.

 

Question 29. Explain how does green house effect cause global warming.
Answer: The greenhouse effect is the process where certain gases in Earth's atmosphere trap heat. Sunlight passes through the atmosphere and warms the Earth's surface. The Earth then radiates some of this heat back towards space as infrared radiation. Greenhouse gases, like carbon dioxide (\( \text{CO}_2 \)), methane (\( \text{CH}_4 \)), and nitrous oxide (\( \text{N}_2\text{O} \)), absorb this outgoing infrared radiation, preventing it from escaping into space. This trapped heat warms the atmosphere. While a natural greenhouse effect is essential for keeping Earth habitable (without it, the average temperature would be about -18°C), human activities, such as burning fossil fuels and deforestation, have significantly increased the concentration of these gases. This intensification of the greenhouse effect leads to an abnormal rise in Earth's average temperature, which is known as global warming. Over the last century, carbon dioxide levels have risen by about 30% and methane by more than double. These trends can cause polar ice caps to melt, leading to rising sea levels and an increased risk of infectious diseases like dengue and malaria.
In simple words: Greenhouse gases in the air trap the sun's heat, keeping Earth warm. But humans are adding too many of these gases, like from burning fuels, which traps too much heat and makes the planet hotter, causing global warming.

🎯 Exam Tip: Clearly explain the two-step process: solar radiation warming Earth, and then greenhouse gases trapping the outgoing infrared radiation. Differentiate the natural effect from its human-enhanced problematic version.

 

Question 30. Mention the standards prescribed by BIS for quality of drinking water.
Answer: The Bureau of Indian Standards (BIS) set specific guidelines in 1991 for the quality of drinking water. These standards cover both physical, chemical, and biological characteristics to ensure water is safe for consumption. For example, the pH should be between 6.5 and 8.5. Total Dissolved Solids (TDS) should not exceed 500 ppm, and Total Hardness (as \( \text{CaCO}_3 \)) is limited to 300 ppm. Nitrate levels should be below 45 ppm, Chloride below 250 ppm, Sulphate below 200 ppm, and Fluoride below 1 ppm. Biologically, there should be no Escherichia Coli (E.Coli) present, and Coliforms should not exceed 10 per 100 ml water sample. Meeting these standards is crucial for public health, as consuming contaminated water can lead to various diseases.

In simple words: The BIS sets rules for safe drinking water, covering things like how acidic it is, how many solids are dissolved, and how many germs are allowed. These rules make sure the water is clean and safe to drink.

🎯 Exam Tip: When listing water quality standards, try to remember a few key physical-chemical parameters (e.g., pH, TDS, Hardness) and at least one biological parameter (e.g., E.Coli) along with their limits.

 

Question 31. How does classical smog differ from photochemical smog?
Answer: Classical smog, also known as London smog or sulf urous smog, was first identified in London in December 1952. It forms mainly in cool, humid conditions and is characterized by a mix of sulfur dioxide (\( \text{SO}_2 \)), sulfur trioxide (\( \text{SO}_3 \)), and particulate matter, often from burning coal. This type of smog is chemically reducing in nature due to the high concentration of \( \text{SO}_2 \) and forms sulphuric acid aerosol when \( \text{SO}_2 \) oxidizes to \( \text{SO}_3 \) and reacts with water. It typically occurs in the mornings and can worsen as the sun rises, leading to respiratory problems and reduced visibility. The primary components are often smoke, fog, and sulfur oxides.
In simple words: Classical smog happens in cold, foggy weather, mainly from burning coal, and has a lot of sulfur dioxide. It's like the old London smog.

🎯 Exam Tip: Differentiate classical smog from photochemical smog by their primary components, formation conditions (temperature, sunlight), and chemical nature (reducing vs. oxidizing). Classical smog is linked to sulfur; photochemical smog to nitrogen oxides and hydrocarbons.

 

II. Write Brief Answer to the Following Questions:

 

Question 21. Dissolved oxygen in water is responsible for aquatic life. What processes are responsible for the reduction in dissolved oxygen in water?
Answer: Several processes lead to a decrease in dissolved oxygen in water. These include the overuse of phosphate and nitrate fertilizers, detergents, and the release of human sewage and organic waste from food, paper, and pulp industries. Microorganisms that break down organic matter also consume oxygen dissolved in the water. Furthermore, at night, aquatic plants continue to breathe but stop photosynthesis, which also lowers the dissolved oxygen levels. This balance is crucial for underwater ecosystems.
In simple words: Too much fertilizer, dirty water, and germs breaking down stuff all use up the oxygen in water, harming fish and other aquatic life.

🎯 Exam Tip: When discussing water pollution, linking specific pollutants (like fertilizers or sewage) to their direct impact on dissolved oxygen is key for a complete answer.

 

Question 22. What would happen if the greenhouse gases were totally missing in the earth's atmosphere?
Answer: If greenhouse gases were entirely absent from Earth's atmosphere, the planet's average surface temperature would drop significantly to about -18°C. Greenhouse gases like carbon dioxide (\( \text{CO}_2 \)), methane (\( \text{CH}_4 \)), ozone (\( \text{O}_3 \)), and chlorofluorocarbons (CFCs) trap heat radiated from the Earth's surface, keeping the atmosphere warm. Without this natural warming effect, most forms of life, including both plants and animals, would not be able to survive on Earth's surface because of the extremely cold temperatures.
In simple words: If there were no greenhouse gases, Earth would be extremely cold, and most living things, including us, could not survive.

🎯 Exam Tip: Remember that the greenhouse effect itself is natural and essential for life; the problem is its intensification by human activities.

 

Question 23. Define smog.
Answer: Smog is a type of air pollution that looks like a smoky fog, made of smoke and fog droplets hanging in the air. It is a chemical blend of gases that often creates a brownish haze over cities. Smog mainly includes ozone near the ground, nitrogen oxides, various organic compounds that evaporate easily, sulfur dioxide, and small solid particles. It can make the air unhealthy to breathe and reduce visibility.
In simple words: Smog is a mix of smoke and fog that pollutes the air, making it hazy and unhealthy, especially in big cities.

🎯 Exam Tip: Distinguish between "classical smog" (smoke + fog + \( \text{SO}_2 \)) and "photochemical smog" (sunlight + nitrogen oxides + hydrocarbons), as they have different compositions and formation conditions.

 

Question 24. Which is considered to be earth's protective umbrella? Why?
Answer: The ozone layer, found high up in the atmosphere, is considered Earth's protective umbrella. It forms a shield of ozone molecules (\( \text{O}_3 \)) that absorbs most of the Sun's harmful ultraviolet (UV) radiation. This protection is vital because UV radiation can cause serious health problems like skin cancer and damage to ecosystems. The ozone layer is constantly being formed and broken down by natural processes involving molecular oxygen, as shown by these reactions:
\( \text{O}_2\text{(g)} \xrightarrow{\text{UV}} \text{O(g)} + \text{O(g)} \)
\( \text{O(g)} + \text{O}_2\text{(g)} \xrightarrow{\text{UV}} \text{O}_3\text{(g)} \)
In simple words: The ozone layer protects Earth by blocking dangerous UV rays from the sun, which helps prevent skin cancer and other harm.

🎯 Exam Tip: Remember that UV radiation helps form ozone but also depletes it; the ozone layer acts as a filter, absorbing harmful UV-B and UV-C radiation.

 

Question 25. What are degradable and non-degradable pollutants?
Answer: Pollutants are divided into two main categories: biodegradable and non-biodegradable, based on how they break down.

**Biodegradable pollutants:** These are substances that nature can easily break down through natural biological processes, usually by microorganisms. This makes them less harmful in the long run.
Example: plant waste, animal waste.

**Non-biodegradable pollutants:** These are substances that natural biological processes cannot break down or decompose easily. They remain in the environment for a very long time, causing continuous harm. This makes them especially dangerous as they accumulate.
Example: Metal wastes (like mercury and lead), DDT, plastics, nuclear waste.
In simple words: Biodegradable pollutants break down easily by nature, like plant scraps. Non-biodegradable pollutants, like plastics or heavy metals, stay in the environment for a very long time because nature cannot break them down.

🎯 Exam Tip: It's important to differentiate between these two types because their management and environmental impact are vastly different.

 

Question 26. From where does ozone come in the photochemical smog?
Answer: In photochemical smog, ozone (\( \text{O}_3 \)) is not directly released but is formed through a series of chemical reactions in the atmosphere, mainly involving nitrogen dioxide (\( \text{NO}_2 \)) and sunlight. Here's how it happens:
\( \text{NO}_2 \xrightarrow{\text{Sun light}} \text{NO} + \text{O} \)
This free oxygen atom then reacts with molecular oxygen to form ozone:
\( \text{O} + \text{O}_2 \rightarrow \text{O}_3 \)
Ozone is a strong oxidizing agent and can react further with unburnt hydrocarbons in the polluted air to create other harmful chemicals like formaldehyde, acrolein, and peroxyacetyl nitrate (PAN). This makes ozone a key component of photochemical smog, especially near ground level.
In simple words: Ozone in photochemical smog is made when sunlight breaks down nitrogen dioxide. The released oxygen then joins with other oxygen to form ozone, which is very reactive and harmful.

🎯 Exam Tip: Highlight that ozone in photochemical smog is ground-level ozone, which is harmful, unlike the beneficial stratospheric ozone layer.

 

Question 27. A person was using water supplied by corporation. Due to shortage of water he started using underground water. He felt laxative effect. What could be the cause?
Answer: The laxative effect experienced by the person suggests that the underground water they started using likely contained an excess amount of sulphates. While a small amount of sulphate ions in water is harmless, concentrations greater than 500 ppm (parts per million) can cause a laxative effect. This is a common issue with groundwater in certain areas, as it can contain dissolved minerals from the soil and rocks. Therefore, the excess sulphates in the underground water are the probable cause of the laxative effect.
In simple words: The person probably got a laxative effect because their underground water had too much sulphate, which can upset the stomach when levels are high.

🎯 Exam Tip: When linking health symptoms to water quality, consider common contaminants and their known effects; high mineral content is often the culprit in underground water.

 

Question 28. What is green chemistry?
Answer: Green chemistry is a scientific approach focused on developing and implementing chemical processes and products that reduce or eliminate the use and generation of hazardous substances. It aims to prevent pollution at its source, rather than just treating it after it has occurred. This field promotes environmentally friendly chemical synthesis, making sure that chemical production is safer for both human health and the environment. It is a vital part of protecting our planet from chemical harm.
In simple words: Green chemistry is about making chemicals and chemical processes that are safe and do not harm the environment or people.

🎯 Exam Tip: Emphasize that green chemistry focuses on preventing pollution by design, rather than cleaning up pollution after it happens.

 

Question 29. Explain how does green house effect cause global warming.
Answer: The greenhouse effect is the process where certain gases in Earth's atmosphere trap heat. These "greenhouse gases" like carbon dioxide (\( \text{CO}_2 \)), methane (\( \text{CH}_4 \)), and water vapor absorb infrared radiation (heat) that the Earth radiates back after being warmed by the sun. This trapped heat warms the Earth's surface and the lower atmosphere. Without this natural effect, Earth's average temperature would be around -18°C, too cold for life. However, human activities, especially the burning of fossil fuels and deforestation, have significantly increased the concentration of these greenhouse gases since the Industrial Revolution. This excess trapping of heat leads to an abnormal rise in the Earth's average global temperature, a phenomenon known as global warming. Global warming can cause melting polar ice caps, rising sea levels, and more extreme weather events.
In simple words: Greenhouse gases in the air trap heat, keeping Earth warm. But too many of these gases from human activities trap too much heat, making the planet warmer and causing global warming.

🎯 Exam Tip: Clearly explain the distinction between the natural, beneficial greenhouse effect and the enhanced greenhouse effect that leads to global warming.

 

Question 30. Mention the standards prescribed by BIS for quality of drinking water.
Answer: The Bureau of Indian Standards (BIS) set specific quality standards for drinking water in 1991 to ensure it is safe for consumption. These standards cover both physical, chemical, and biological characteristics, outlining the desirable limits for various parameters. Meeting these guidelines is essential for public health.

In simple words: The BIS sets rules for how clean our drinking water should be, including limits for things like pH, hardness, and how many germs can be in it, to make sure it's safe to drink.

🎯 Exam Tip: When listing water quality standards, try to recall a few key parameters and their limits, especially for pH, TDS, and harmful bacteria.

 

Question 31. How does classical smog differ from photochemical smog?
Answer: Classical smog and photochemical smog are two different types of air pollution, differing in their formation, composition, and typical environments.

**Classical Smog (also known as London Smog or Reducing Smog):**
Classical smog was first noticed in London in December 1952. It is made up of a mixture of sulfur dioxide (\( \text{SO}_2 \)), sulfur trioxide (\( \text{SO}_3 \)), and humidity, often combined with coal smoke and fog. It forms in cool, humid conditions, typically in the mornings, and gets worse as the sun rises. Chemically, it is "reducing" in nature due to its high \( \text{SO}_2 \) content, which is oxidized to \( \text{SO}_3 \) and then reacts with water to form sulphuric acid aerosols.

**Photochemical Smog (also known as Los Angeles Smog or Oxidizing Smog):**
Photochemical smog was first observed in Los Angeles in 1950. It occurs in warm, dry, and sunny climates. This type of smog is formed when sunlight reacts with air pollutants like nitrogen oxides and hydrocarbons, along with smoke, dust, and fog. It tends to form and worsen in the afternoon when sunlight is strongest. Chemically, it is "oxidizing" in nature because it contains high concentrations of oxidizing agents such as nitrogen dioxide (\( \text{NO}_2 \)) and ozone (\( \text{O}_3 \)). The key difference is the role of sunlight and the types of chemicals involved, leading to different environmental conditions for each type of smog.
In simple words: Classical smog happens in cool, wet weather and involves sulfur. Photochemical smog happens in warm, sunny weather and involves sunlight reacting with car exhaust fumes.

🎯 Exam Tip: Focus on the key differences: climate/conditions, primary pollutants (sulfur vs. nitrogen oxides/hydrocarbons), and chemical nature (reducing vs. oxidizing).

 

Question 32. What are particulate pollutants? Explain any three.
Answer: Particulate pollutants are tiny solid particles or liquid droplets that float in the air. Many of these small particles are dangerous to breathe in because they can cause health problems. Here are three types:
1. **Suspended Particles/Droplets:** These are very small solid pieces like dust, pollen, smoke, or soot, and also tiny liquid droplets called aerosols. They can come from many sources and stay in the air for a long time.
2. **Smoke Particulates:** Smoke is made up of fine solid particles, or a mix of solid and liquid particles, created when organic materials burn. Examples include smoke from cigarettes, burning oil, fossil fuels, garbage, and dry leaves.
3. **Dust:** Dust is made of fine solid particles that come from crushing or grinding solid materials. For example, sand from sandblasting, sawdust from woodworking, cement dust from factories, and fly ash from power plants are all forms of dust pollutants. These particles are often small enough to be inhaled deeply into the lungs.
In simple words: Particulate pollutants are tiny bits of solid or liquid in the air. Examples include dust, smoke from burning things, and tiny particles from crushing materials.

🎯 Exam Tip: When explaining particulate pollutants, remember to mention their small size and the fact that they are suspended in the air, making them easily inhalable.

 

Question 33. Even though the use of pesticides increases crop production, they adversely affect the living organisms. Explain the function and the adverse effects of the pesticides.
Answer: Pesticides are chemicals used in farming to kill or stop unwanted organisms like pests, weeds, and fungi, which helps increase crop production. However, these chemicals can also be harmful to humans and other living things. Pesticides are grouped by their targets:

**1. Insecticides:** These kill insects. Examples like DDT, BHC, and aldrin can stay in the soil for a long time. They are absorbed by plants and can contaminate root crops such as carrots and radishes. They accumulate in the food chain, causing harm to higher organisms.

**2. Fungicides:** These kill fungi. Organomercury compounds are commonly used. When they get into the soil, they break down and release highly toxic mercury.

**3. Herbicides:** These kill unwanted plants, also known as weed killers. Examples include sodium chlorate (\( \text{NaClO}_3 \)) and sodium arsenite (\( \text{Na}_3\text{AsO}_3 \)). Many herbicides are toxic to mammals, affecting their health directly or indirectly through the food chain.
In simple words: Pesticides kill pests to grow more food but can harm people and animals. Different types like insecticides, fungicides, and herbicides all have dangerous chemicals that can stay in the environment.

🎯 Exam Tip: When discussing pesticides, remember to mention their long-term environmental persistence and how they move through the food chain, affecting non-target organisms.

 

Question 34. Ethane burns completely in air to give \( \text{CO}_2 \), while in a limited supply of air gives \( \text{CO} \). The same gases are found in automobile exhaust. Both \( \text{CO} \) and \( \text{CO}_2 \) are atmospheric pollutants.
Answer: The main carbon oxide pollutants in the atmosphere are carbon monoxide (\( \text{CO} \)) and carbon dioxide (\( \text{CO}_2 \)).

(i) **Carbon Monoxide (\( \text{CO} \)):** This is a very poisonous gas. It is formed when fuels like coal and firewood do not burn completely. Cars and other vehicles release a lot of \( \text{CO} \) into the air through their exhaust. When \( \text{CO} \) is inhaled, it strongly binds with haemoglobin in the blood, forming carboxyhaemoglobin. This prevents the blood from carrying enough oxygen to the body, leading to oxygen deficiency. This gas is especially dangerous because it is colorless and odorless, making it hard to detect.

(ii) **Carbon Dioxide (\( \text{CO}_2 \)):** This gas is released into the atmosphere mainly through natural processes like respiration and the decomposition of organic matter, but also from burning fossil fuels, forest fires, and cement production. While plants use \( \text{CO}_2 \) for photosynthesis, converting it into carbohydrates and oxygen, increased levels of \( \text{CO}_2 \) from human activities are a major cause of global warming. High levels of \( \text{CO}_2 \) in the atmosphere trap more heat, leading to a rise in Earth's temperature and causing problems like headaches and nausea.
In simple words: Carbon monoxide is a dangerous gas from incomplete burning that stops blood from carrying oxygen. Carbon dioxide, from burning fuels and breathing, helps plants but too much of it makes the Earth too hot.

🎯 Exam Tip: Differentiate between \( \text{CO} \) (toxic, binds to haemoglobin) and \( \text{CO}_2 \) (greenhouse gas, essential for plants but excess causes warming).

 

Question 35. On the basis of chemical reactions involved, explain how do CFC's cause depletion of ozone layer in stratosphere?
Answer: Chlorofluorocarbons (CFCs) are chemicals that cause significant damage to the ozone layer in the stratosphere. Here’s how they do it through a series of chemical reactions:
When CFCs like \( \text{CF}_2\text{Cl}_2 \) reach the stratosphere, they are broken down by powerful UV radiation, releasing highly reactive chlorine free radicals:
\( \text{CF}_2\text{Cl}_2 \xrightarrow{\text{hv}} \text{CF}_2\text{Cl} + \text{Cl} \)

This free chlorine radical then reacts with ozone (\( \text{O}_3 \)), breaking it down into oxygen (\( \text{O}_2 \)) and forming chlorine monoxide (\( \text{ClO} \)) radical:
\( \text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2 \)

The \( \text{ClO} \) radical then reacts with a free oxygen atom (which is also formed from ozone breakdown by UV light), regenerating the chlorine radical:
\( \text{ClO} + \text{O} \rightarrow \text{Cl} + \text{O}_2 \)

Since the chlorine radical is regenerated at the end of the cycle, it can go on to destroy many more ozone molecules. This continuous attack by chlorine radicals thins the ozone layer, leading to the formation of "ozone holes." It is estimated that one single reactive chlorine atom can destroy as many as 100,000 molecules of ozone in the stratosphere, highlighting the severe impact of CFCs. Protecting the ozone layer is crucial for blocking harmful UV radiation from reaching Earth.
In simple words: CFCs release chlorine in the upper atmosphere. This chlorine then breaks down ozone, and the chlorine is reused to break down more ozone, creating holes in our protective ozone layer.

🎯 Exam Tip: Remember to show the cyclic nature of the chlorine radical in the ozone depletion mechanism, emphasizing that it's regenerated and can destroy many ozone molecules.

 

Question 36. How is acid rain formed? Explain its effect.
Answer: Acid rain is formed when air pollutants, mainly oxides of sulfur and nitrogen, react with water, oxygen, and other chemicals in the atmosphere. Normally, rainwater has a pH of about 5.6 due to dissolved carbon dioxide (\( \text{CO}_2 \)). However, when sulfur dioxide (\( \text{SO}_2 \)) and nitrogen oxides (\( \text{NO}_2 \)) are released from sources like burning fossil fuels (coal, oil) in power plants and motor vehicles, they get absorbed by water droplets in clouds. These oxides then convert into sulfuric acid and nitric acid, lowering the rainwater's pH below 5.6, thus creating acid rain.

The key chemical reactions involved are:
\( 2\text{SO}_2 + \text{O}_2 + 2\text{H}_2\text{O} \rightarrow 2\text{H}_2\text{SO}_4 \)
\( 4\text{NO}_2 + \text{O}_2 + 2\text{H}_2\text{O} \rightarrow 4\text{HNO}_3 \)

**Effects of Acid Rain:**
Acid rain has several harmful effects on the environment. It can damage buildings and statues, especially those made of marble or limestone, by corroding them. It acidifies lakes and streams, harming aquatic life, and can damage forests by stripping leaves of essential nutrients. Acid rain also affects soil chemistry, making it harder for plants to absorb nutrients. It can also contaminate drinking water and harm human health through respiratory problems.
In simple words: Acid rain happens when pollution from burning fuels makes sulfur and nitrogen gases mix with water in the air, creating strong acids that fall as rain. This rain harms buildings, forests, and water bodies, affecting plants and animals.

🎯 Exam Tip: For acid rain, clearly state the primary pollutants (\( \text{SO}_2 \), \( \text{NO}_2 \)), their sources, and the resulting acids. Mentioning a few diverse effects (buildings, aquatic life, forests) is important.

 

Question 37. What is sewage? What are the major steps involved in the treatment of sewage waste?
Answer: Sewage, also known as wastewater, is the dirty water that goes down drains from homes, businesses, and industries. It contains various pollutants, including organic matter, chemicals, and disease-causing microorganisms. Treating sewage is crucial to remove these harmful substances before the water is released back into the environment. The major steps involved in wastewater treatment are:

**Objectives of Waste Water Treatment:**
1. To change harmful compounds into harmless ones.
2. To remove any bad smells.
3. To get rid of solid materials from the sewage.
4. To kill disease-causing germs.

**Treatment Process:**
The sewage treatment process involves several stages:

**I. Preliminary Treatment:**
In this first step, large solid items and floating impurities are removed. This is done by passing the wastewater through bar screens and mesh screens, which catch bigger debris. This step prevents damage to later equipment.

**II. Primary Treatment (or Settling Process):**
Here, a significant amount of the suspended inorganic and organic solids are removed by letting them settle out of the liquid sewage. To speed up this settling, chemicals called coagulants (like alum or ferrous sulphate) are often added. These coagulants form large, jelly-like clumps that trap smaller organic matter, which then settles to the bottom as sludge.
\( \text{Al}_2(\text{SO}_4)_3 + 6\text{H}_2\text{O} \rightarrow 2\text{Al}(\text{OH})_3 \downarrow + 3\text{H}_2\text{SO}_4 \)

**III. Secondary Treatment (or Biological Treatment):**
This stage uses biological processes to remove biodegradable organic impurities. Aerobic bacteria break down these pollutants. About 90% of the oxygen-demanding wastes are removed in this step, which includes processes like trickling filters or activated sludge.

(a) **Trickling Filter Process:**
A trickling filter uses a circular tank filled with coarse or crushed rock. Sewage is sprayed evenly over this bed using slowly rotating arms. As the water trickles down, microorganisms grow on the surface of the filtering material and consume the organic waste. This process helps to clean the water biologically.
*Diagram Description:* This process involves raw sewage being screened and passed through a primary treatment (sedimentation). The effluent then flows to a "Fettling tank" where air is introduced. This aerated water is then sent to a "Trickling filter," a bed of media (like rocks) over which the water is sprayed. Microorganisms grow on the media, breaking down organic matter. The treated water then goes through further sedimentation and chlorination before being released as effluent.

(b) **Activated Sludge Process:**
Activated sludge is a mixture of biologically active sewage containing many aerobic bacteria, which efficiently break down organic impurities. The effluent from primary treatment is mixed with a small amount of activated sludge and aerated in a tank. The microorganisms quickly oxidize the organic impurities. After aeration, the mixture goes to a sedimentation tank where the activated sludge settles. A portion of this settled sludge is returned to aerate new incoming sewage to "seed" the process. This method removes about 90-95% of BOD (Biochemical Oxygen Demand).
*Diagram Description:* This shows a flow from "Sewage effluent, from primary treatment" into an "Aeration tank" where "Air supply" is added. From there, it moves to a "Sedimentation tank." Sludge settles at the bottom, and part of this "Sludge settled at the bottom" is recirculated back to the aeration tank as "Activate sludge." The clear water from the sedimentation tank is "Effluent for drainage."

**IV. Tertiary Treatment:**
After secondary treatment, the sewage effluent still has some remaining BOD (around 25 ppm). Tertiary treatment further cleans the water. It involves introducing the effluent into a flocculation tank where lime is added to remove phosphates. The water then moves to an ammonia stripping tower, where the pH is raised to 11, converting ammonium ions (\( \text{NH}_4^+ \)) into gaseous ammonia (\( \text{NH}_3 \)). Finally, the effluent passes through an activated charcoal column, which absorbs any remaining minute organic wastes. The water is then disinfected with chlorine.

**V. Disposal of Sludge:**
The sludge generated from the various treatment steps needs to be properly disposed of. Common methods include:
1. Dumping it into low-lying areas.
2. Burning it (incineration).
3. Dumping it into the sea.
4. Using it as low-grade fertilizer.
*Overall Treatment Plant Diagram Description:* This flowchart illustrates the entire sewage treatment process. "Raw sewage" first undergoes "Screening" and then enters a "Coagulant" stage, followed by "Sedimentation." The resulting effluent moves to an "Activate sludge" tank. From there, it can either go to a "Trickling filter" or a "Secondary treatment" process which includes "Chlorination" and further "Sedimentation" to produce "Treated sewage" for discharge. The sludge collected at various stages is indicated for disposal.
In simple words: Sewage is dirty water. Treating it involves removing big trash, then letting solids settle, next using good bacteria to eat organic waste, and finally, using chemicals and filters to make the water very clean before safely releasing it. The leftover mud (sludge) is then disposed of.

🎯 Exam Tip: Remember the three main stages of sewage treatment (Primary, Secondary, Tertiary) and the purpose of each. Be able to describe the basic function of a trickling filter or activated sludge process.

 

Question 38. Differentiate the following:
(i) BOD and COD
(ii) Viable and non-viable particulate pollutants.
Answer: Here's a comparison of the requested terms:

(i) **BOD and COD:** These are measures used to assess the organic pollution in water.

(ii) **Viable and Non-Viable Particulate Pollutants:** These categories describe tiny particles in the air based on whether they are alive or not.

**Viable Particulates:** These are small, living organisms dispersed in the air. They include things like bacteria, fungi, molds, and algae. Some fungi can cause allergies in people, and these particulates can also spread diseases to plants. They are biological in nature and can reproduce.

**Non-Viable Particulates:** These are small, non-living solid particles and liquid droplets suspended in the air. They can help transport viable particles. There are four main types of non-viable particulates found in the atmosphere: smoke (tiny solid/liquid particles from burning), dust (fine solid particles from crushing/grinding), mists (liquid droplets from condensation), and fumes (fine solid particles from chemical reactions).
In simple words: BOD measures oxygen used by germs to break down waste, while COD measures oxygen needed by chemicals to break down all waste. Viable particles are living things like bacteria in the air, but non-viable particles are non-living, like dust or smoke.

🎯 Exam Tip: For BOD and COD, remember BOD reflects biodegradable organic matter over a longer period, while COD measures all oxidizable organic matter more quickly. For particulates, the key is whether they are living organisms (viable) or non-living matter (non-viable).

 

Question 39. Explain how oxygen deficiency is cause by carbon monoxide in our blood? Give its effect.
Answer: Carbon monoxide (\( \text{CO} \)) is a dangerous gas produced when coal or wood burns incompletely, and it's also a major component of car exhaust. It causes oxygen deficiency in our blood because it binds much more strongly to hemoglobin (the substance in red blood cells that carries oxygen) than oxygen does. When \( \text{CO} \) binds to hemoglobin, it forms carboxyhemoglobin, which is very stable. This prevents hemoglobin from carrying the normal amount of oxygen from the lungs to the body's tissues and organs. As a result, the oxygen-carrying capacity of the blood is greatly reduced. The body's cells and organs don't get enough oxygen, leading to serious health problems. This problem is particularly dangerous because \( \text{CO} \) is odorless and colorless, making it difficult to detect without special sensors. An enriching sentence here is that this strong binding capacity of carbon monoxide makes it a silent killer in enclosed spaces.

**Effects of Oxygen Deficiency:**
This lack of oxygen in the blood can lead to a range of severe effects, including headaches, dizziness, tension, loss of consciousness, blurred vision, and even heart attacks. In severe cases, prolonged exposure to carbon monoxide can be fatal. Efforts to control environmental pollution, including carbon monoxide emissions, are crucial for public health and have led to the development of "green chemistry" principles focused on environmentally friendly chemical synthesis.
In simple words: Carbon monoxide stops our blood from carrying enough oxygen because it sticks to blood cells much tighter than oxygen. This lack of oxygen can cause headaches, dizziness, and even be deadly if not treated.

🎯 Exam Tip: The critical point is \( \text{CO} \)'s higher affinity for hemoglobin compared to \( \text{O}_2 \). Mentioning carboxyhemoglobin and specific health effects (headache, dizziness, cardiac arrest) is important.

 

Question 40. What are the various methods you suggest to protect our environment from pollution?
Answer: Protecting our environment from pollution requires a mix of strategies and individual actions. Here are several methods to help:
1. **Waste Management:** Properly dispose of all waste materials. This includes sorting waste for recycling and ensuring that hazardous waste is handled safely to prevent it from contaminating soil and water.
2. **Recycling:** Reuse or recycle as much disposed waste material as possible. Recycling reduces the amount of waste sent to landfills and conserves natural resources, converting waste into useful forms.
3. **Safer Solvents:** In industrial processes, switch from highly toxic solvents to less toxic alternatives. This practice, often part of green chemistry, reduces the release of harmful chemicals.
4. **Cleaner Fuels:** Use fuels that have lower pollutant content, such as washed coal (which has reduced sulfur). This minimizes the release of harmful gases when burned.
5. **Plant More Trees:** Growing more trees helps absorb carbon dioxide, purify the air, and support biodiversity, which are all vital for a healthy environment. Forests are often called the lungs of the planet.
6. **Vehicle Emission Control:** Implement and enforce measures to control pollution from vehicle exhausts. This includes catalytic converters and regular vehicle maintenance to ensure lower emissions.
7. **Green Chemistry Adoption:** Continue developing and using green chemistry principles for chemical synthesis. This means designing chemical products and processes that are environmentally friendly and reduce hazardous substances from the start.
In simple words: To protect our environment, we should manage waste well, recycle more, use less toxic chemicals, burn cleaner fuels, plant more trees, control vehicle pollution, and create safer chemistry methods.

🎯 Exam Tip: When suggesting methods, aim for a balanced list that includes individual actions, industrial changes, and natural solutions like planting trees.

 

I. Choose the Best Answer:

 

Question 1. The type of pollution cause by spraying of DDT is
(a) air and soil
(b) air and water
(c) air
(d) air, water and soil
Answer: (d) air, water and soil
In simple words: DDT spreads through the air when sprayed, lands on soil, and washes into water, polluting all three parts of the environment.

🎯 Exam Tip: Remember that persistent organic pollutants like DDT can travel through multiple environmental compartments due to their mobility and resistance to breakdown.

 

Question 2. The green house effect is caused by
(a) \( \text{CO}_2 \)
(b) \( \text{NO}_2 \)
(c) \( \text{NO} \)
(d) \( \text{CO} \)
Answer: (a) \( \text{CO}_2 \)
In simple words: Carbon dioxide is a main gas that traps heat in Earth's atmosphere, causing the greenhouse effect.

🎯 Exam Tip: While other gases contribute, carbon dioxide is the most significant greenhouse gas due to its abundance and human-induced emissions.

 

Question 3. The gas responsible for ozone depletion:
(a) \( \text{NO} \) and freons
(b) \( \text{SO}_2 \)
(c) \( \text{CO}_2 \)
(d) \( \text{CO} \)
Answer: (a) \( \text{NO} \) and freons
In simple words: Nitrogen oxide and freons (CFCs) are the main gases that break down the ozone layer.

🎯 Exam Tip: Freons (chlorofluorocarbons or CFCs) and nitrogen oxides are the primary human-made and natural (for NO) substances that destroy stratospheric ozone.

 

Question 4. In Antarctica ozone depletion is due to the formation of following compound
(a) acrolein
(b) peroxyacetyl nitrate
(c) \( \text{SO}_2 \) and \( \text{NO}_2 \)
(d) chlorine nitrate
Answer: (d) chlorine nitrate
In simple words: In Antarctica, chlorine nitrate plays a key role in the complex chemical reactions that cause the ozone layer to thin out.

🎯 Exam Tip: Polar stratospheric clouds facilitate reactions that convert inactive chlorine compounds like chlorine nitrate into active forms that deplete ozone, especially in Antarctic winters.

 

Question 5. The main element of smog is
(a) \( \text{O}_3 \) and PAN
(b) \( \text{O}_3 \)
(c) PAN
(d) PPN and PBN
Answer: (a) \( \text{O}_3 \) and PAN
In simple words: Ozone and PAN (Peroxyacetyl Nitrate) are two major harmful chemicals found in smog.

🎯 Exam Tip: Ozone (\( \text{O}_3 \)) and Peroxyacetyl Nitrate (PAN) are characteristic components of photochemical smog, which is typically found in sunny urban areas.

 

Question 6. Classical smog occurs in places of
(a) excess \( \text{SO}_2 \)
(b) low temperature
(c) high temperature
(d) excess \( \text{NH}_3 \)
Answer: (b) low temperature
In simple words: Classical smog forms in cold weather, usually when there is also a lot of smoke and fog.

🎯 Exam Tip: Remember that classical smog (London smog) is associated with cool, humid conditions and sulfur dioxide, contrasting with photochemical smog which requires warm, sunny conditions.

 

Question 7. Which gas is responsible for 'Bhopal Gas Tragedy' in 1984?
(a) \( \text{CO} \)
(b) Methyl isocyanate
(c) \( \text{SO}_2 \) and \( \text{NO}_2 \)
(d) Ethyl isocyanate
Answer: (b) Methyl isocyanate
In simple words: The gas that caused the disaster in Bhopal in 1984 was methyl isocyanate.

🎯 Exam Tip: The Bhopal Gas Tragedy is a historic environmental disaster, and methyl isocyanate (MIC) is the specific toxic chemical involved, making it a key factual recall item.

 

Question 8. Which gas is a main reason behind air pollution, is produced by
(a) sewage pollutant
(b) aerosols
(c) industrial remains
(d) All of the options
Answer: (b) aerosols
In simple words: Aerosols are tiny particles floating in the air that greatly contribute to air pollution.

🎯 Exam Tip: Aerosols, while also being propellants, are significant air pollutants themselves, and this question is likely referring to the tiny particulate matter that can stay suspended in the air.

 

Question 9. Which is a dangerous radiological pollutant?
(a) \( \text{C}^{14} \)
(b) \( \text{S}^{35} \)
(c) \( \text{Sr}^{90} \)
(d) \( \text{P}^{32} \)
Answer: (c) \( \text{Sr}^{90} \)
In simple words: Strontium-90 is a dangerous radioactive substance that can harm living things.

🎯 Exam Tip: Strontium-90 is particularly dangerous because it behaves like calcium in the body, accumulating in bones and causing long-term health issues.

 

Question 10. Which is related to 'Green House Effect'?
(a) Farming of Green Plants
(b) Farming of Vegetables in Houses
(c) Global Warming
(d) Biodegradable pollutant
Answer: (c) Global Warming
In simple words: The greenhouse effect is directly linked to global warming, which is the warming of Earth's climate.

🎯 Exam Tip: Global warming is the consequence of an enhanced greenhouse effect caused by increased greenhouse gas concentrations.

 

Question 11. The uppermost region of the atmosphere is called
(a) Ionosphere
(b) Mesosphere
(c) Troposphere
(d) Stratosphere
Answer: (d) Stratosphere
In simple words: The stratosphere is the highest layer of Earth's atmosphere from the given options, where the ozone layer is located.

🎯 Exam Tip: Remember the order of atmospheric layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere. The question implies "uppermost" among the options given, not the absolute uppermost layer.

 

Question 12. Which of the following is the coldest region of atmosphere
(a) Thermosphere
(b) Mesosphere
(c) Troposphere
(d) Stratosphere
Answer: (b) Mesosphere
In simple words: The mesosphere is the part of the atmosphere that gets the coldest.

🎯 Exam Tip: The temperature decreases with altitude in the mesosphere, reaching its lowest point at the mesopause, making it the coldest region of Earth's atmosphere.

 

Question 13. The region which is greatly affected by air pollution is
(a) Thermosphere
(b) Stratosphere
(c) Troposphere
(d) Mesosphere
Answer: (c) Troposphere
In simple words: The troposphere, which is the lowest layer of the atmosphere, is most impacted by air pollution because that's where most human activities and emissions happen.

🎯 Exam Tip: Most air pollution occurs in the troposphere because it is the layer closest to the Earth's surface where human activities and industrial processes release pollutants.

 

Question 14. The substance which is a primary pollutant?
(a) \( \text{H}_2\text{SO}_4 \)
(b) \( \text{CO} \)
(c) PAN
(d) Aldehydes
Answer: (b) \( \text{CO} \)
In simple words: Carbon monoxide is a primary pollutant because it is released directly into the air from sources like burning fuels.

🎯 Exam Tip: Primary pollutants are emitted directly into the atmosphere, while secondary pollutants (like \( \text{H}_2\text{SO}_4 \), PAN, and aldehydes from this list) form from reactions between primary pollutants.

 

Question 15. Depletion of ozone layer causes
(a) breast cancer
(b) blood cancer
(c) lung cancer
(d) skin cancer
Answer: (d) skin cancer
In simple words: When the ozone layer gets thinner, more harmful UV rays reach Earth, which can cause skin cancer.

🎯 Exam Tip: Ozone layer depletion increases the penetration of UV-B radiation, which is directly linked to an increased risk of skin cancer and cataracts in humans.

 

Question 16. Formation of London smog takes place in
(a) Winter during day time
(b) summer during day time
(c) summer during morning time
(d) winter during morning time
Answer: (d) winter during morning time
In simple words: London smog usually forms in cold winter mornings due to the combination of smoke, fog, and still air.

🎯 Exam Tip: London smog (classical smog) is characteristic of cold, humid conditions, typically in winter mornings, due to temperature inversions trapping pollutants.

 

Question 17. The substance which is not regarded as a pollutant?
(a) \( \text{NO}_2 \)
(b) \( \text{CO}_2 \)
(c) \( \text{O}_3 \)
(d) Hydrocarbons
Answer: (b) CO2
In simple words: Carbon dioxide is naturally present in the atmosphere and is essential for life, so it is not considered a pollutant in normal amounts, unlike the others which are harmful. It helps plants grow.

🎯 Exam Tip: Remember that while \( \text{CO}_2 \) is a greenhouse gas, its natural presence and role in biological cycles mean it's not strictly a "pollutant" unless in excessive, human-induced concentrations.

 

Question 18. Green house gases
(a) allow shorter wavelength to enter earth's atmosphere while doesn't allow longer wavelength to leave the earth's atmosphere.
(b) allow longer wavelength to enter earth atmosphere while doesn't allow shorter wavelength to leave the surface.
(c) don't have wavelength specific character.
(d) she wavelength specific behaviour near the earth while far from earth these have wavelength independent behavior.
Answer: (a) allow shorter wavelength to enter earth's atmosphere while doesn't allow longer wavelength to leave the earth's atmosphere.
In simple words: Greenhouse gases let sunlight (short waves) pass through to Earth, but they trap the heat (long waves) trying to leave. This makes the Earth warmer, like a blanket.

🎯 Exam Tip: Understanding the difference between short-wavelength incoming solar radiation and long-wavelength outgoing infrared radiation is key to explaining the greenhouse effect.

 

Question 19. Carbon monoxide (CO) is harmful to man because
(a) it forms carbolic acid
(b) it generates excess \( \text{CO}_2 \)
(c) it is carcinogenic
(d) it competes with \( \text{O}_2 \) for haemoglobin
Answer: (d) it competes with O2 for haemoglobin
In simple words: Carbon monoxide is very dangerous because it takes the place of oxygen in your blood. It sticks to the red blood cells much more easily than oxygen, stopping your body from getting the oxygen it needs.

🎯 Exam Tip: The high affinity of carbon monoxide for hemoglobin (about 200-250 times that of oxygen) is the critical fact an examiner looks for.

 

Question 20. Today the concentration of green house gases is very high because of
(a) use of refrigerator
(b) increased combustion of oils and coal
(c) deforestation
(d) All of the options
Answer: (d) All of the options
In simple words: The amount of greenhouse gases is increasing a lot because people use refrigerators, burn more fuel like oil and coal, and cut down many trees. All these actions add more of these gases to the air.

🎯 Exam Tip: When "All of the options" is an choice, consider if each individual option contributes to the problem; if so, it's often the correct answer for comprehensive environmental issues.

 

Question 21. The quantity of \( \text{CO}_2 \) in atmosphere is
(a) 3.34%
(b) 6.5%
(c) 0.034 %
(d) 0.34%
Answer: (c) 0.034 %
In simple words: Carbon dioxide makes up a very small part of the air we breathe, only about 0.034 percent. Even this small amount is crucial for Earth's temperature balance and plant life.

🎯 Exam Tip: Memorize the approximate percentage of key atmospheric gases like nitrogen, oxygen, argon, and carbon dioxide for quick recall.

 

Question 22. BOD of pond is connected with
(a) microbes & organic matter
(b) organic matter
(c) microbes
(d) None of the options
Answer: (a) microbes & organic matter
In simple words: The BOD (Biochemical Oxygen Demand) of a pond shows how much oxygen is used up by tiny living things (microbes) as they break down natural materials (organic matter) in the water. High BOD means lots of microbes are working, using a lot of oxygen.

🎯 Exam Tip: Always remember that BOD directly measures the oxygen consumed by microorganisms when decomposing organic waste in water, indicating pollution levels.

 

Question 23. When rain is accompanied by a thunderstorm, the collected rain water will have a pH value
(a) slightly lower than that of rain water without thunderstorm
(b) slightly higher than that when the thunderstorm is not there
(c) uninfluenced by occurrence of thunderstorm
(d) which depends upon the amount of dust in air
Answer: (a) slightly lower than that of rain water without thunderstorm
In simple words: Rain during a thunderstorm is often more acidic than regular rain. This is because lightning creates nitrogen oxides, which mix with water to form nitric acid.

🎯 Exam Tip: Note that lightning in thunderstorms produces nitrogen oxides (\( \text{NO}_x \)), which can dissolve in rainwater to form nitric acid, lowering the pH.

 

Question 24. Water pollution is caused by
(a) pesticides
(b) \( \text{SO}_2 \)
(c) \( \text{O}_2 \)
(d) \( \text{CO}_2 \)
Answer: (a) pesticides
In simple words: Pesticides, which are chemicals used to kill pests, are a major cause of water pollution when they wash off land into rivers and lakes. While other options relate to air pollution, pesticides directly harm water quality.

🎯 Exam Tip: Distinguish between primary pollutants for air (like \( \text{SO}_2 \), \( \text{CO}_2 \)) and water (like pesticides, heavy metals, sewage).

 

Question 25. Minamata disease of Japan is due to pollution of
(a) Aresenic
(b) Lead
(c) Cynide
(d) Mercury
Answer: (d) Mercury
In simple words: Minamata disease, which first happened in Japan, is caused by severe mercury poisoning. People got sick from eating seafood that had been contaminated with mercury from industrial waste.

🎯 Exam Tip: Remember Minamata disease as a classic example of heavy metal (mercury) poisoning through the food chain, highlighting the impact of industrial pollution.

 

Question 26. Which causes death of fish in water bodies polluted by sewage?
(a) Foul smell
(b) Pathogens
(c) Herbicides
(d) Decrease in D.O.
Answer: (d) Decrease in D.O.
In simple words: When water gets polluted by sewage, the amount of oxygen dissolved in it (D.O.) drops sharply. Fish need this oxygen to breathe, so a lack of it causes them to die.

🎯 Exam Tip: The critical factor for aquatic life in polluted water is often the reduction in Dissolved Oxygen (D.O.) due to the decomposition of organic matter by microorganisms.

 

Question 27. Sewage water is purified by
(a) aquatic plants
(b) microorganisms
(c) light
(d) fishes
Answer: (b) microorganisms
In simple words: Sewage water is cleaned mainly by tiny living things called microorganisms. These microbes break down the harmful waste in the water, making it safer.

🎯 Exam Tip: In wastewater treatment, the biological treatment stage heavily relies on the action of various microorganisms to decompose organic pollutants.

 

Question 28. Which pollutant is harmful for 'Tajmahal'?
(a) Hydrogen
(b) \( \text{O}_2 \)
(c) \( \text{SO}_2 \)
(d) Chlorine
Answer: (c) SO2
In simple words: Sulfur dioxide (\( \text{SO}_2 \)) from air pollution is especially bad for monuments like the Taj Mahal. It reacts with moisture in the air to form acid rain, which slowly corrodes the marble.

🎯 Exam Tip: Remember that acid rain, primarily caused by sulfur dioxide and nitrogen oxides, is the main threat to limestone and marble structures like the Taj Mahal.

 

Question 29. Negative soil pollution is
(a) reduction in soil productivity due to erosion and over use
(b) reduction in soil productivity due to addition of pesticides and industrial wastes
(c) converting fertile land into barren land by dumping ash, sludge and garbage
(d) None of the options
Answer: (a) reduction in soil productivity due to erosion and over use
In simple words: Negative soil pollution means the soil becomes less able to grow crops because it has been worn away by erosion or used too much without rest. It's about losing the soil's natural goodness.

🎯 Exam Tip: Differentiate between "negative" soil pollution (loss of inherent fertility) and "positive" soil pollution (addition of harmful substances).

 

Question 30. The quantity of DDT in food chain
(a) decreases
(b) remains same
(c) increases
(d) changes
Answer: (c) increases
In simple words: When DDT enters a food chain, its amount goes up as you move from smaller animals to larger ones. This is called bio-magnification, where the harmful chemical builds up in each step.

🎯 Exam Tip: This question refers to biomagnification, where non-biodegradable pollutants like DDT accumulate in increasing concentrations at higher trophic levels in a food chain.

 

Question 31. Which is known as "Third poison of environment” and also creates 'Blue baby syndrome'
(a) Nitrate present in water
(b) Phosphate and detergents found in water
(c) Cyanide
(d) Pesticides
Answer: (b) Phosphate and detergents found in water
In simple words: Excess phosphates and detergents in water can cause a problem called "Blue Baby Syndrome." This happens when nitrates (which can be formed from excess phosphates) get into drinking water, especially affecting babies by reducing their blood's ability to carry oxygen. Phosphates and detergents are often linked to eutrophication, a key environmental concern.

🎯 Exam Tip: Blue Baby Syndrome (methemoglobinemia) is primarily caused by excessive nitrates in drinking water, which can result from agricultural runoff (nitrate fertilizers) and decomposition of organic matter by phosphates and detergents. While the primary cause is nitrate, phosphate and detergents contribute to the conditions leading to high nitrate levels.

 

Question 32. The substance having the largest concentration in acid rain?
(a) \( \text{H}_2\text{CO}_3 \)
(b) \( \text{HNO}_3 \)
(c) HCI
(d) \( \text{H}_2\text{SO}_4 \)
Answer: (d) H2SO4
In simple words: Sulfuric acid (\( \text{H}_2\text{SO}_4 \)) is usually the most common and concentrated acid found in acid rain. It forms from sulfur dioxide released when fossil fuels are burned.

🎯 Exam Tip: Sulfur dioxide emissions from burning fossil fuels are the primary source for sulfuric acid in acid rain, making \( \text{H}_2\text{SO}_4 \) typically the most abundant acidic component.

 

Question 33. Water is often treated with chlorine to
(a) remove hardness
(b) increase oxygen content
(c) kill germs
(d) remove suspended particles
Answer: (c) kill germs
In simple words: Chlorine is added to water to kill harmful bacteria and other tiny living things (germs) that can make us sick. It's a key step in making drinking water safe.

🎯 Exam Tip: Disinfection, often using chlorine, is a crucial step in water treatment to eliminate pathogens and ensure the water is safe for consumption.

 

Question 34. Thermal pollution affects mainly
(a) vegetation
(b) aquatic creature
(c) rocks
(d) air
Answer: (b) aquatic creature
In simple words: Thermal pollution, which is when water gets too hot, mostly harms animals and plants that live in water. Changes in water temperature can make it hard for them to live and breathe.

🎯 Exam Tip: Focus on how changes in water temperature directly impact the dissolved oxygen levels and metabolic rates of aquatic organisms, making them the most vulnerable.

 

Question 35. B.O.D test or biochemical oxygen demand test is made for measuring
(a) air pollution
(b) water pollution
(c) noise pollution
(d) soil pollution
Answer: (b) water pollution
In simple words: The BOD test is used to find out how much organic waste is in water and how polluted it is. It measures how much oxygen tiny living things need to break down that waste.

🎯 Exam Tip: Always remember that BOD is a key indicator specifically for organic pollution in water bodies.

 

Question 36. Brewery and sugar factory water alters the quality of a water body by increasing
(a) temperature
(b) turbidity
(c) pH
(d) COD and BOD
Answer: (d) COD and BOD
In simple words: Water discharged from breweries and sugar factories has a lot of organic material. This increases the Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) of the water, making it more polluted and harmful for aquatic life.

🎯 Exam Tip: Industrial effluents, especially from food processing like breweries and sugar factories, are rich in organic matter, which directly contributes to high COD and BOD values in receiving water bodies.

 

Question 37. A dental disease characterized by mottling of teeth is due to the presence of a certain chemical element in drinking water. Which is that element?
(a) Boron
(b) Chlorine
(c) Fluorine
(d) Mercury
Answer: (c) Fluorine
In simple words: Mottling of teeth, which causes white or brown spots, is a dental problem caused by too much fluoride in drinking water. While some fluoride is good for teeth, too much can be harmful.

🎯 Exam Tip: Excessive fluoride intake, often from natural sources in groundwater, leads to dental fluorosis (mottling) and skeletal fluorosis.

 

Question 38. The high amount of E.coli in water is an indicator of
(a) hardness of water
(b) industrial pollution
(c) sewage pollution
(d) presence of chlorine in the water
Answer: (c) sewage pollution
In simple words: A lot of E.coli bacteria in water tells us that the water is likely polluted with human or animal waste (sewage). E.coli itself is not always harmful, but its presence means harmful germs from sewage might also be there.

🎯 Exam Tip: E.coli is a common indicator bacteria for fecal contamination, meaning the water has been exposed to sewage or animal waste, potentially containing harmful pathogens.

 

Question 39. A lake with an inflow of domestic sewage rich in organic waste may result in
(a) drying of the lake very soon due to algal bloom
(b) an increase production of fish due to a lot of nutrients
(c) death of fish due to lack of oxygen
(d) increased population of aquatic food web organisms
Answer: (c) death of fish due to lack of oxygen
In simple words: If a lake gets a lot of sewage with organic waste, tiny plants (algae) grow very fast, using up oxygen. When these algae die, they are broken down by bacteria which use even more oxygen, leading to a severe lack of oxygen that kills the fish.

🎯 Exam Tip: The key consequence of sewage inflow is eutrophication, leading to algal blooms and subsequent oxygen depletion (anoxia), which is lethal to most fish species.

 

Question 40. In which one of the following the BOD (Biochemical Oxygen Demand) of sewage(S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order
(a) \( \text{SE < S < PE < DE} \)
(b) \( \text{SE < PE < S < DE} \)
(c) \( \text{PE < S < SE < DE} \)
(d) \( \text{S < DE < PE < SE} \)
Answer: (c) PE < S < SE < DE
In simple words: When we look at how much oxygen is needed to break down waste from different sources, paper mill waste needs the least, then regular sewage, then sugar mill waste, and finally, distillery waste needs the most oxygen. This shows distillery waste is the most polluting among these.

🎯 Exam Tip: BOD values indicate the organic load; generally, industrial effluents like distillery waste have very high BOD due to concentrated organic matter compared to municipal sewage or other industrial wastes.

 

Question 41. The greenhouse effect is because of the
(a) presence of gases, which in general are strong infrared absorbers, in the atmosphere
(b) presence of \( \text{CO}_2 \) only in the atmosphere
(c) presence of \( \text{O}_3 \) and \( \text{CH}_4 \) in the atmosphere
(d) \( \text{N}_2\text{O} \) and chlorofluoro hydrocarbons in the atmosphere
Answer: (a) presence of gases, which in general are strong infrared absorbers, in the atmosphere
In simple words: The Earth gets warmer because certain gases in the air can soak up heat that tries to leave our planet. These gases are good at absorbing heat energy, keeping it close to Earth.

🎯 Exam Tip: The fundamental mechanism of the greenhouse effect is the absorption of outgoing long-wave (infrared) radiation by specific atmospheric gases.

 

Question 42. Which of the following is/are the hazardous pollutant(s) present in automobile exhaust gases?
(a) \( \text{N}_2 \)
(b) CO
(c) \( \text{CH}_4 \)
(d) Oxides of nitrogen
Answer: (c) CH4
In simple words: Car exhaust contains many harmful substances, and methane (\( \text{CH}_4 \)) is one of them. While CO and oxides of nitrogen are also major pollutants, methane is a potent greenhouse gas and a hazardous component.

🎯 Exam Tip: Major hazardous pollutants from automobile exhaust include carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (like methane, \( \text{CH}_4 \)), and particulate matter.

 

Question 43. Green chemistry means such reactions which:
(a) produce colour during reactions
(b) reduce the use and production of hazardous chemicals
(c) are related to the depletion of ozone layer
(d) study the reactions in plants
Answer: (b) reduce the use and production of hazardous chemicals
In simple words: Green chemistry is a way of designing chemical products and processes that reduce or remove the need for harmful chemicals. It focuses on making everything safer for people and the environment.

🎯 Exam Tip: Green chemistry's core principle is sustainability: minimizing the generation and use of hazardous substances in chemical design and manufacturing.

 

Question 44. Which one of the following statement is not true?
(a) pH of drinking water should be between 5.5 - 9.5.
(b) Concentration of DO below 6 ppm is good for the growth of fish.
(c) Clean water would have a BOD value of less than 5 ppm.
(d) Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant.
Answer: (b) Concentration of DO below 6 ppm is good for the growth of fish.
In simple words: It is not true that a low amount of dissolved oxygen (below 6 ppm) is good for fish. Fish need enough oxygen to live, and lower levels mean the water is unhealthy for them. High levels of oxygen are good for fish.

🎯 Exam Tip: Remember that sufficient dissolved oxygen (DO) is vital for aquatic life; levels below 5-6 ppm are often stressful or lethal for many fish species.

 

Question 45. Which one of the following statements regarding photochemical smog is not correct?
(a) Carbon monoxide does not play any role in photochemical smog formation.
(b) photochemical smog is an oxidizing agent in character.
(c) photochemical smog is formed through photochemical reaction involving solar energy.
(d) Photochemical smog does not cause irritation in eyes and throat.
Answer: (d) Photochemical smog does not cause irritation in eyes and throat.
In simple words: The statement that photochemical smog does not irritate eyes and throat is wrong. In reality, this type of smog, which forms in sunny cities, causes a lot of discomfort, including stinging eyes and breathing problems.

🎯 Exam Tip: Photochemical smog is known for its oxidizing nature and irritant properties, causing respiratory issues and eye irritation due to components like ozone and PAN.

 

Question 46. Frequent occurrence of water blooms in a lake indicates
(a) nutrient deficiency
(b) oxygen deficiency
(c) excessive nutrient availability
(d) absence of herbivores in the lake
Answer: (b) oxygen deficiency
In simple words: When a lake often has lots of water blooms (fast growth of algae), it usually means there is not enough oxygen in the water. These blooms use up a lot of oxygen, especially when they die and break down. This can harm other living things in the lake.

🎯 Exam Tip: Algal blooms (eutrophication) lead to a subsequent decomposition by bacteria, which consumes large amounts of dissolved oxygen, causing oxygen deficiency.

 

Question 47. The smog is essentially caused by the presence of
(a) Oxides of sulphur and nitrogen
(b) \( \text{O}_2 \) and \( \text{N}_2 \)
(c) \( \text{O}_2 \) and \( \text{O}_3 \)
(d) \( \text{O}_2 \) and \( \text{N}_2 \)
Answer: (a) Oxides of sulphur and nitrogen
In simple words: Smog, especially industrial smog, is mainly caused by harmful gases like sulfur oxides and nitrogen oxides in the air. These gases come from burning fuels and mix with fog or smoke to create the thick haze we call smog.

🎯 Exam Tip: Classical (London) smog is primarily due to \( \text{SO}_2 \) and particulate matter, while photochemical (Los Angeles) smog involves nitrogen oxides and volatile organic compounds.

 

Question 48. Identify the wrong statement in the following.
(a) Chlorofluorocarbons are responsible for ozone layer depletion.
(b) Greenhouse effect is responsible for global warming.
(c) Ozone layer does not permit infrared radiation from the sun to reach the earth.
(d) Acid rain is mostly because of oxides of nitrogen and sulphur.
Answer: (c) Ozone layer does not permit infrared radiation from the sun to reach the earth.
In simple words: The wrong statement is that the ozone layer blocks infrared radiation from the sun. Actually, the ozone layer mostly blocks harmful ultraviolet (UV) radiation, not infrared. Infrared radiation is absorbed by greenhouse gases, which warms the Earth.

🎯 Exam Tip: Clearly distinguish the roles of the ozone layer (blocks UV) and greenhouse gases (trap infrared) in atmospheric processes.

 

Question 49. Identify the incorrect statement from the following.
(a) Ozone absorbs the intense ultraviolet radiation of the sun.
(b) Depletion of ozone layer is because of its chemical reactions with chlorofluoro alkanes.
(c) Ozone absorbs infrared radiation.
(d) Oxides of nitrogen in the atmosphere can cause the depletion of ozone layer.
Answer: (c) Ozone absorbs infrared radiation.
In simple words: The statement that ozone absorbs infrared radiation is incorrect. Ozone mainly absorbs ultraviolet (UV) radiation from the sun, protecting Earth. Other greenhouse gases are responsible for absorbing infrared radiation.

🎯 Exam Tip: Reiterate the specific function of ozone: it is a strong absorber of ultraviolet (UV) radiation, while other greenhouse gases like \( \text{CO}_2 \) and water vapor absorb infrared radiation.

 

Question 50. What is DDT among the following?
(a) Greenhouse gas
(b) A fertilizer
(c) Biodegradable pollutant
(d) Non - biodegradable pollutant
Answer: (d) Non - biodegradable pollutant
In simple words: DDT is a type of chemical that does not break down easily in nature. Because of this, it stays in the environment for a long time and can build up in living things, causing harm.

🎯 Exam Tip: DDT is a classic example of a persistent organic pollutant (POP) that undergoes biomagnification in food chains because it is non-biodegradable.

 

Question 51. The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was:
(a) Methyl isocyanate
(b) Methylamine
(c) Ammonia
(d) Phosgene
Answer: (a) Methyl isocyanate
In simple words: The very dangerous gas that leaked during the Bhopal gas tragedy was called Methyl Isocyanate. This chemical caused a huge disaster and many deaths.

🎯 Exam Tip: The Bhopal Gas Tragedy is a landmark environmental disaster; explicitly remembering "Methyl Isocyanate" (MIC) as the leaked gas is essential.

 

Question 52. Black - foot disease is caused due to groundwater contaminated with excess of
(a) Nitrate
(b) Fluoride
(c) Arsenic
(d) Sulphur
Answer: (c) Arsenic
In simple words: Black-foot disease is a serious illness that comes from drinking groundwater with too much arsenic. This metal contaminates water in some areas and leads to this specific health problem.

🎯 Exam Tip: Associate specific diseases with their primary pollutant causes; Black-foot disease is strongly linked to arsenic contamination in drinking water.

 

Question 53. Exposure of an organism to UV system causes
(a) photodynamic action
(b) formation of thymidine
(c) splitting of H - bonds of DNA
(d) splitting of phosphodiester bonds
Answer: (c) splitting of H - bonds of DNA
In simple words: When living things are exposed to too much ultraviolet (UV) light, it can damage their DNA. Specifically, UV radiation causes the hydrogen bonds within the DNA structure to break, which can lead to genetic problems.

🎯 Exam Tip: The primary harmful effect of UV radiation on DNA is the formation of pyrimidine dimers, which involves the breaking and rearrangement of bonds, and can lead to mutations.

 

Question 54. Under column - I, a list of gases that are known to have a greenhouse effect is given. Relate them to their main source selecting from the given under Column - II:

(a) A - 3, B - 4, C - 5, D - 1, E - 2
(b) A - 5, B - 1, C - 3, D - 4, E - 2
(c) A - 4, B - 5, C - 1, D - 2, E - 3
(d) A - 1, B - 3, C - 4, D - 5, E - 2
Answer: (a) A - 3, B - 4, C - 5, D - 1, E - 2
In simple words: This match correctly links each greenhouse gas to its main source. Nitrous oxide comes from denitrification, CFCs from refrigerators, methane from cattle and rice fields, ozone from car exhausts (as a secondary pollutant), and carbon dioxide from burning fossil fuels.

🎯 Exam Tip: For matching questions, systematically go through each option and eliminate those that are clearly wrong. Knowing the main sources of major greenhouse gases is crucial.

 

Question 55. Minamata disease is a pollution related disease results form
(a) oil spills into sea
(b) accumulation of arsenic into atmosphere
(c) release of industrial waste mercury into bodies water
(d) release human organic waste into drinking water
Answer: (c) release of industrial waste mercury into bodies water
In simple words: Minamata disease is caused by industrial factories releasing mercury waste into water bodies. This mercury gets into fish and then into people who eat the fish, causing severe health problems.

🎯 Exam Tip: This question directly tests knowledge of a specific pollution-related disease. Remember that Minamata disease is unequivocally linked to mercury poisoning.

 

Question 56. Air pollution causing photochemical oxidants production include
(a) Carbon monoxide, sulphur dioxide
(b) Nitrous oxide, nitric acid fumes, nitric oxide
(c) Ozone, peroxyacetyl nitrate, aldehydes
(d) Oxygen, chlorine, fuming nitric acid
Answer: (c) Ozone, peroxyacetyl nitrate, aldehydes
In simple words: Photochemical oxidants, which are harmful substances in smog, include ozone, peroxyacetyl nitrate (PAN), and aldehydes. These are formed when sunlight reacts with other pollutants in the air.

🎯 Exam Tip: Key components of photochemical smog (oxidants) are ozone (\( \text{O}_3 \)), PAN (peroxyacetyl nitrate), and aldehydes, formed by reactions involving \( \text{NO}_x \) and VOCs in sunlight.

 

Question 57. Photochemical smog formed in congested metropolitan cities mainly consists of
(a) ozone, peroxyacetyl nitrate and \( \text{NO}_x \)
(b) smoke, peroxyacetyl nitrate and \( \text{SO}_2 \)
(c) hydrocarbons, \( \text{SO}_2 \) and \( \text{CO}_2 \)
(d) hydrocarbons, ozone and \( \text{SO}_x \)
Answer: (a) ozone, peroxyacetyl nitrate and NOx
In simple words: Photochemical smog, common in busy cities, is mainly made up of ozone (\( \text{O}_3 \)), peroxyacetyl nitrate (PAN), and nitrogen oxides (\( \text{NO}_x \)). These form through chemical reactions in sunlight.

🎯 Exam Tip: The primary constituents of photochemical smog are secondary pollutants formed by sunlight-driven reactions involving nitrogen oxides and volatile organic compounds.

 

Question 58. Which, one of the following statements is correct?
(a) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies
(b) Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants
(c) Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and potassium for plant nutrition in soil
(d) At present it is not possible to grow maize without chemical fertilizers
Answer: (a) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies
In simple words: Using too much chemical fertilizer can cause lakes and rivers nearby to become overfed with nutrients. This leads to excessive growth of algae, a process called eutrophication, which can harm aquatic life.

🎯 Exam Tip: Excessive nutrient runoff (especially nitrogen and phosphorus) from agricultural fields treated with chemical fertilizers is the leading cause of eutrophication in water bodies.

 

Question 59. Reducing the use of non-biodegradable things will contribute of
(a) Increase in O2
(b) Cyanophycean blooms occur
(c) Depletion of O2 layers
(d) Eutrophication
Answer: (a) Increase in O2
In simple words: When we use fewer non-biodegradable items, it helps increase the amount of oxygen available, which is good for the environment. This is because fewer harmful things need to be broken down, saving oxygen.

🎯 Exam Tip: Understanding the terms 'biodegradable' and 'non-biodegradable' is key to answering questions about environmental impact and pollution control.

 

Question 60. Which of the following metal is a water pollutant and causes sterility in human being?
(a) As
(b) Mn
(c) Mg
(d) Hg
Answer: (b) Mn
In simple words: Manganese (Mn) is a metal that can pollute water and has been linked to problems with fertility in people. It's important to keep metals like this out of our drinking water.

🎯 Exam Tip: Memorize the common water pollutants and their specific health effects for exam success.

 

Question 61. Lichens do not like to grow in cities
(a) because of absence of the right type of algae and fungi
(b) because of lack of moisture
(c) because of SO2 pollution
(d) because natural habitat is missing
Answer: (c) because of SO2 pollution
In simple words: Lichens do not grow well in cities because the air often has a lot of sulfur dioxide (SO2) pollution. Lichens are very sensitive to air pollution.

🎯 Exam Tip: Lichens are excellent bio-indicators of air quality because of their sensitivity to pollutants like sulfur dioxide. Remember this key fact.

 

Question 62. Limit of BOD prescribed by Central pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is
(a) < 100 ppm
(b) < 30 ppm
(c) < 3.0 ppm
(d) < 10 ppm
Answer: (b) < 30 ppm
In simple words: The government board that deals with pollution says that wastewater released into natural waters should have a Biological Oxygen Demand (BOD) value of less than 30 parts per million. This helps keep the water clean.

🎯 Exam Tip: Knowing specific regulatory limits like BOD values for water discharge can demonstrate a detailed understanding of environmental standards.

 

Question 63. Which one of the following pairs is mismatched
(a) Fossil fuel burning - release of CO2
(b) Nuclear power - radioactive wastes
(c) Solar energy - Greenhouse effect
(d) Biomass burning - release of CO2
Answer: (c) Solar energy - Greenhouse effect
In simple words: Solar energy is clean energy from the sun and does not cause the greenhouse effect. The greenhouse effect is caused by gases that trap heat in the atmosphere.

🎯 Exam Tip: Understand which energy sources are clean and which contribute to environmental issues like the greenhouse effect. Solar energy is generally considered green and non-polluting.

 

Question 64. In a coal fired power plant electrostatic precipitators are installed to control emission of
(a) SO2
(b) NOx
(c) SPM
(d) CO
Answer: (c) SPM
In simple words: Electrostatic precipitators are used in power plants that burn coal to catch tiny solid particles (Suspended Particulate Matter) before they are released into the air. This helps clean the air.

🎯 Exam Tip: Be familiar with different pollution control technologies and what specific pollutants they are designed to remove.

 

Question 65. The term "Bio - magnification" refers to the
(a) growth of organism due to food consumption
(b) increase in population size
(c) blowing up of environmental issues by man
(d) increase in the concentration of non - degradable pollutants as they pass through food chain
Answer: (d) increase in the concentration of non - degradable pollutants as they pass through food chain
In simple words: Biomagnification is when harmful substances, like certain chemicals, become more and more concentrated in living things as you go up the food chain. For example, tiny amounts in plants can become large amounts in top predators.

🎯 Exam Tip: Differentiate between biomagnification (increase in concentration up the food chain) and bioaccumulation (increase in concentration within an organism over its lifetime).

 

Question 66. In almost all Indian metropolitan cities like Delhi, the major atmospheric pollutant(s) is / are
(a) suspended particulate matter (SPM)
(b) oxides of sulphur
(c) carbon dioxide and carbon monoxide
(d) oxides of nitrogen
Answer: (a) suspended particulate matter (SPM)
In simple words: In big cities in India, tiny solid particles floating in the air, called suspended particulate matter (SPM), are a main cause of air pollution. These particles can come from vehicles and factories.

🎯 Exam Tip: Recognize common urban air pollutants and their sources to understand city-specific environmental challenges.

 

Question 67. In coming years, skin related disorders will be more common due to
(a) pollutants in air
(b) use of detergents
(c) water pollution
(d) depletion of ozone layer
Answer: (d) depletion of ozone layer
In simple words: If the ozone layer gets thinner, more harmful UV rays from the sun can reach us. This extra radiation can cause more skin problems in the future.

🎯 Exam Tip: Connect environmental issues like ozone depletion directly to their specific human health consequences, such as increased skin disorders.

 

Question 68. Statement 1: Inhabitants close to very busy airports are likely to experience health hazards. Statement 2: Sound level of jet aeroplanes usually exceeds 160 dB.
(a) Statement - 1 is True, Statement - 2 is True, Statement - 2 is a correct explanation for Statement - 1.
(b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement - 1
(c) Statement - 1 is True, Statement - 2 is False
(d) Statement - 1 is False, Statement - 2 is True
Answer: (a) Statement - 1 is True, Statement - 2 is True, Statement - 2 is a correct explanation for Statement - 1.
In simple words: Both statements are true. People living near noisy airports face health risks, and jet planes are very loud, often exceeding 160 dB. The loud noise from planes is why living near airports is bad for health.

🎯 Exam Tip: For assertion-reason questions, first determine if each statement is true, then evaluate if Statement 2 logically explains Statement 1.

 

Question 69. Statement 1: Suspended particulate matter (SPM) is an important pollutant released by diesel vehicles. Statement 2: Catalytic converters greatly reduce pollution caused by automobiles.
(a) Statement - 1 is True, Statement - 2 is True, Statement -2 is a correct explanation for Statement - 1.
(b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement -1
(c) Statement - 1 is True, Statement - 2 is False
(d) Statement - 1 is False, Statement - 2 is True
Answer: (b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement -1
In simple words: Both statements are correct: diesel vehicles release harmful tiny particles (SPM), and catalytic converters do help reduce car pollution. However, the second statement does not explain why SPM is released from diesel vehicles.

🎯 Exam Tip: Always check if the second statement *explains* the first, not just if both statements are true on their own.

 

Question 70. Statement 1: Eutrophication shows increase in productivity in water. Statement 2: With increasing eutrophication, the diversity of the phytoplankton increases.
(a) Statement - 1 is True, Statement - 2 is True, Statement -2 is a correct explanation for Statement - 1.
(b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement - 1
(c) Statement - 1 is True, Statement - 2 is False
(d) Statement - 1 is False, Statement - 2 is True
Answer: (b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement - 1
In simple words: Statement 1 is true because eutrophication leads to more plant growth in water. Statement 2 is also true as more plant growth can increase phytoplankton diversity. However, the second statement does not directly explain the overall increase in productivity mentioned in the first statement.

🎯 Exam Tip: Eutrophication often leads to an *initial* increase in productivity and then a *decrease* in biodiversity due to oxygen depletion. Be careful with how "diversity" is used in the context of these questions.

 

Question 71. Statement 1: The main cause of the Bhopal gas tragedy was phosgene. Statement 2: Phosgene is a volatile liquid.
(a) Statement - 1 is True, Statement - 2 is True, Statement -2 is a correct explanation for Statement - 1.
(b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement -1
(c) Statement - 1 is True, Statement - 2 is False
(d) Statement - 1 is False, Statement - 2 is True
Answer: (d) Statement - 1 is False, Statement - 2 is True
In simple words: Statement 1 is false because the Bhopal gas tragedy was caused by methyl isocyanate, not phosgene. Statement 2 is true because phosgene is a liquid that easily turns into gas.

🎯 Exam Tip: Know the specific chemical involved in major historical industrial disasters, such as methyl isocyanate for the Bhopal gas tragedy.

 

Question 72. Statement 1: CO2 causes green house effect. Statement 2: Other gases do not show such effect.
(a) Statement - 1 is True, Statement - 2 is True, Statement -2 is a correct explanation for Statement - 1
(b) Statement - 1 is True, Statement - 2 is True, Statement - 2 is not a correct explanation for statement - 1
(c) Statement - 1 is True, Statement - 2 is False
(d) Statement - 1 is False, Statement - 2 is True
Answer: (c) Statement - 1 is True, Statement - 2 is False
In simple words: Carbon dioxide (CO2) does cause the greenhouse effect by trapping heat, so statement 1 is true. However, statement 2 is false because other gases like methane and nitrous oxide also cause the greenhouse effect.

🎯 Exam Tip: Remember that several gases, not just CO2, are responsible for the greenhouse effect and global warming.

 

II. Very Short Question And Answers (2 Marks)

 

Question 1. What is called as environmental pollution?
Answer: Environmental pollution is any unwanted change in our surroundings that harms plants, animals, and people. It means when the environment becomes dirty or unsafe. For example, smoke in the air is a type of pollution.

🎯 Exam Tip: When defining pollution, highlight the "undesirable change" and "harmful effects" as key components of the definition.

 

Question 2. What are pollutants?
Answer: Pollutants are the substances or materials that cause environmental pollution. They can be harmful to nature and living things. For example, plastic waste is a common pollutant.

🎯 Exam Tip: A simple, clear definition of pollutants focuses on their role as agents of pollution rather than just their composition.

 

Question 3. Write the different types of atmospheric pollution.
Answer: The different types of atmospheric pollution are:
1. Air pollution
2. Water pollution
3. Soil pollution
All these types of pollution affect the quality of our planet in different ways.

🎯 Exam Tip: Clearly list the main categories of pollution as air, water, and soil pollution for a comprehensive answer.

 

Question 4. What is Air pollution?
Answer: Air pollution is any harmful change in the air that negatively affects living things. This pollution mainly happens in the lower and upper parts of the atmosphere, known as the troposphere and stratosphere. It is mostly caused by too many unwanted substances being released into the air. This can make it hard for plants and animals to breathe. For example, car exhaust contributes to air pollution.

🎯 Exam Tip: Define air pollution by mentioning its impact on living organisms and the specific atmospheric regions it affects.

 

Question 5. What are the techniques adopt to reduce particulate pollutants?
Answer: To reduce tiny solid or liquid particles (particulate pollutants) from the air, several methods are used. These include electrostatic precipitators, gravity settling chambers, wet scrubbers, and cyclone collectors. These tools work by either washing away the particles or letting them settle down. For example, precipitators use electricity to collect dust. These techniques are often used in factories to clean exhaust gases.

🎯 Exam Tip: List specific technologies for controlling particulate pollution and briefly explain their general principle of operation (washing or settling).

 

Question 6. Define soil pollution.
Answer: Soil pollution happens when harmful substances like toxic compounds, radioactive materials, chemical salts, and disease-causing agents build up in the soil. This buildup harms plant growth and animal health. For instance, too much chemical fertilizer can pollute the soil.

🎯 Exam Tip: The definition of soil pollution should highlight the "buildup of persistent toxic compounds" and their negative impact on living organisms.

 

Question 7. Write the effects that were caused by classical smog.
Answer: Classical smog has several harmful effects:
1. It is a main reason for acid rain.
2. It makes it hard to see, which affects air and road travel.
3. It can cause irritation in the breathing tubes (bronchial irritation).
Smog can reduce visibility greatly, making roads dangerous.

🎯 Exam Tip: When listing effects, always ensure they are distinct and directly attributable to the pollutant in question, like acid rain and visibility issues for classical smog.

 

III. Short Question And Answers (3 Marks)

 

Question 1. How the oxides of nitrogen pollute the atmospheric air?
Answer: Oxides of nitrogen are formed when nitrogen burns at high temperatures, like in engines or power plants that use coal, diesel, or petrol. Nitrogen in the air combines with oxygen to form nitric oxide (NO), which then reacts with more oxygen to form nitrogen dioxide (NO2).
\( \text{N}_2 + \text{O}_2 \xrightarrow{>1210^\circ \text{C}} 2\text{NO} \)
\( 2\text{NO} + \text{O}_2 \xrightarrow{1100^\circ \text{C}} 2\text{NO}_2 \)
\( \text{NO} + \text{O}_3 \rightarrow \text{NO}_2 + \text{O}_2 \)
These oxides turn into nitric acid, which causes acid rain. They also create a reddish-brown haze in heavy traffic and can harm plant leaves, slowing down photosynthesis. Nitrogen dioxide also irritates the lungs, leading to asthma and lung damage, and can harm textiles and metals. In urban areas, these oxides are key ingredients in photochemical smog.

🎯 Exam Tip: Explain both the formation of nitrogen oxides and their multiple environmental impacts, including acid rain, plant damage, and respiratory issues, for a complete answer.

 

Question 2. How the hydrocarbon compounds make harmful effects on living things?
Answer: Hydrocarbon compounds, which are made only of carbon and hydrogen, have harmful effects on living things. They are found naturally, like marsh gas, and are also released from vehicles when fuel doesn't burn completely. Many of these hydrocarbons can cause cancer. For example, polycyclic aromatic hydrocarbons (PAH) are known to cause cancer and can irritate the eyes and the soft tissues lining our body parts, such as the inside of the nose. These compounds can accumulate in the environment and affect organisms over time.

🎯 Exam Tip: Focus on the carcinogenic nature of hydrocarbons and their direct irritant effects on living organisms when discussing their harmful impacts.

 

Question 3. Explain the environmental impact of ozone depletion.
Answer: Ozone is naturally formed and broken down, keeping a balance in the stratosphere. However, if this balance is disturbed and the ozone layer gets thinner (depleted), it allows more harmful UV rays from the sun to reach Earth. This can cause skin cancer and weaken people's immune systems. UV radiation also damages plant proteins, leading to harmful changes in cells. It affects the growth of tiny ocean plants called phytoplankton, which then disrupts the ocean's food chain and harms fish. The ozone layer acts like Earth's sunscreen, protecting all life.

🎯 Exam Tip: When explaining ozone depletion, emphasize the increase in UV radiation, its specific health impacts (skin cancer, immune suppression), and ecological effects (phytoplankton, food chain disruption).

 

Question 4. Write the causes of water pollution.
Answer: Water pollution can be caused by several factors:
(i) **Microbiological (Pathogens):** Harmful microorganisms like bacteria, viruses, and protozoa are major water pollutants. They come from domestic sewage and animal waste. These pathogens can contaminate fish and shellfish, making people who eat them sick with diseases like polio and cholera. Human waste can carry bacteria such as E. coli and Streptococcus faecalis, causing stomach and gut problems.
(ii) **Organic Wastes:** Organic materials such as leaves, grass, and other trash also pollute water. Too much growth of tiny water plants (phytoplankton) due to these wastes causes pollution. Microorganisms in the water break down this organic matter, using up the oxygen in the water. This lack of oxygen can harm other aquatic life. Industrial waste and agricultural runoff also add organic matter.

🎯 Exam Tip: Categorize the causes of water pollution (e.g., microbiological, organic) and provide specific examples for each to demonstrate a thorough understanding.

 

Question 5. Write a short note on Eutrophication.
Answer: Eutrophication is a process where water bodies get too many nutrients, which causes a lot of plant growth, especially algae (algae bloom). This thick growth of algae covers the water surface and uses up a lot of the oxygen in the water. When oxygen levels drop, it becomes hard for other living things like fish to survive, leading to their death. This process reduces the number of different living organisms in the water, which is called a loss of biodiversity. It often happens when fertilizers and sewage run into lakes and rivers. This creates an imbalance in the aquatic ecosystem.

🎯 Exam Tip: Explain eutrophication by focusing on the excess nutrients, resulting algae bloom, oxygen depletion, and its ultimate impact on aquatic biodiversity.

 

Question 6. Write the harmful effects those caused by chemical water pollutants.
Answer: Chemical water pollutants can have severe harmful effects on health:
1. Cadmium and mercury can damage the kidneys.
2. Lead poisoning can seriously harm the kidneys, liver, brain, and also affects the central nervous system.
3. Polychlorinated biphenyls (PCBs) can cause skin diseases and are known to cause cancer. These chemicals can enter the water from industrial waste and persist in the environment for a long time.

🎯 Exam Tip: List specific chemical pollutants and their corresponding health impacts (e.g., lead and neurological damage, PCBs and cancer) to show detailed knowledge.

 

Question 7. Distinguish between BOD and COD.
Answer:

In simple words: BOD measures how much oxygen bacteria need to break down waste in water. COD measures how much oxygen is needed to break down all organic waste using strong chemicals. BOD takes longer, while COD is faster.

🎯 Exam Tip: Clearly differentiate BOD and COD by their definition (biological vs. chemical oxidation), the time taken for the test, and their primary application in assessing water quality.

 

IV. Long Question And Answer (5 Marks)

 

Question 1. Explain the different layers of earth's atmosphere.
Answer: The Earth's atmosphere has several important layers:
**Troposphere:** This is the lowest layer of the atmosphere, extending from the Earth's surface up to about 10 km. Around 80% of the atmosphere's total mass is found in this layer. The troposphere is where most weather events occur, such as clouds, rain, and snow. It is important because it is where living things breathe.
This troposphere is often discussed in relation to other parts of the Earth system:
(i) **Hydrosphere:** This includes all the water sources on Earth like oceans, seas, rivers, lakes, streams, underground water, and polar icecaps. It covers about 75% of the Earth's surface, which is why Earth is often called the "Blue Planet." Water is essential for all life forms.
(ii) **Lithosphere:** This layer consists of the solid parts of the Earth, including soil, rocks, and mountains. It forms the landmasses and the solid crust beneath them.
(iii) **Biosphere:** This is the part of Earth where life exists. It combines the lithosphere, hydrosphere, and atmosphere, integrating all living organisms within these different environments. The biosphere is like a thin skin around the Earth where everything alive interacts.

🎯 Exam Tip: When describing atmospheric layers, provide their approximate altitude, key characteristics, and importance to life or weather patterns.

 

Question 2. How the oxides of sulphur pollute the atmospheric air?
Answer: Oxides of sulfur, mainly sulfur dioxide (\( \text{SO}_2 \)) and sulfur trioxide (\( \text{SO}_3 \)), are produced when fuels containing sulfur, like coal, are burned, or when sulfide ores are processed. Sulfur dioxide is a toxic gas that harms both animals and plants. It can cause eye irritation, coughing, asthma, and bronchitis in humans. This gas can make it difficult for animals and plants to breathe. The presence of tiny particles in polluted air helps sulfur dioxide turn into more harmful sulfur trioxide:
\( 2\text{SO}_2 + \text{O}_2 \xrightarrow{\text{Particular matter}} 2\text{SO}_3 \)
When sulfur trioxide mixes with water vapor in the atmosphere, it forms sulfuric acid (\( \text{H}_2\text{SO}_4 \)), which then falls as acid rain:
\( \text{SO}_3 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_4 \)
Acid rain damages buildings, plants, and aquatic life, showing the widespread impact of sulfur oxides on our environment.

🎯 Exam Tip: Explain the formation of sulfur oxides, their direct health and environmental effects, and their role in the creation of acid rain, including the relevant chemical equations.

 

Question 3. Explain the health effects of particulate pollutants for human health.
Answer: Particulate pollutants are tiny particles in the air, such as dust, mist, and fumes, which are dangerous for human health. Here are their health effects:
1. Particles larger than 5 microns usually settle in the nasal passage. However, smaller particles, about 10 microns, can easily enter the lungs, causing scarring or fibrosis (thickening) of the lung lining. This can make breathing difficult.
2. These particles irritate the lungs and can lead to cancer and asthma. One such disease is pneumoconiosis, where coal miners may develop "black lung disease" and textile workers may suffer from "white lung disease."
3. Lead particles are especially harmful to children's brains and can interfere with the normal development of red blood cells. They can also lead to cancer.
4. Particulate matter in the atmosphere reduces visibility, which is dangerous for aircraft and motor vehicles. This is due to the scattering and absorption of sunlight.
5. Particulates act as centers for cloud formation, which can increase fog and rain, making conditions worse.
6. These particles can settle on plant leaves, blocking the pores and reducing the plants' ability to take in carbon dioxide, which affects photosynthesis. Thus, air quality directly affects human health and well-being.

🎯 Exam Tip: List the health effects of particulate pollutants clearly, differentiating between lung damage, chronic diseases, and specific impacts like lead poisoning in children. Include effects on visibility and plants to show broader understanding.

 

Question 4. Explain the effects of photo chemical smog and its control.
Answer: Photochemical smog is a mixture mainly composed of nitrogen oxides, ozone, and oxidized hydrocarbons like formaldehyde (\( \text{HCHO} \)), acrolein (\( \text{CH}_2 = \text{CH} - \text{CHO} \)), and peroxyacetyl nitrate (PAN). This type of smog can irritate the eyes, skin, and lungs, and it increases the risk of asthma. High levels of ozone and nitric oxide (NO) can irritate the nose and throat, cause chest pain, and make breathing uncomfortable. PAN is toxic to plants, attacking younger leaves and causing them to turn bronze or glossy. Smog also corrodes metals, stones, building materials, and painted surfaces, causing widespread damage to infrastructure. This type of smog is often seen in sunny, dry climates.

**Control of Photochemical Smog:**
Photochemical smog can be reduced by stopping the release of nitrogen oxides and hydrocarbons into the atmosphere. This can be done by using catalytic converters in vehicle engines, which convert harmful gases into less harmful ones. Planting certain trees, such as Pinus, Pyrus, Quercus Vitus, and Juniperus, can help by absorbing and breaking down nitrogen oxide. Reducing vehicle emissions is a key step in controlling this type of air pollution.

🎯 Exam Tip: Clearly define the components of photochemical smog, detail its effects on human health, plants, and materials, and then outline practical control measures like catalytic converters and specific plant species.

 

Question 5. List out the major water pollutants and their sources.
Answer: Major water pollutants and their sources are listed below:

In simple words: Water gets polluted by many things. Tiny living things like bacteria come from sewage. Food waste and detergents are organic wastes. Farm chemicals make water dirty. Factories also release heavy metals like mercury and lead.

🎯 Exam Tip: When listing pollutants, pairing each with its primary source provides a complete and easily understandable overview of water pollution.

 

Question 6. What are the major sources that cause soil pollution?
Answer: Soil pollution comes from various sources, making the land unhealthy for plants and animals. The main sources include:
1. **Artificial Fertilizers:** Farmers use these to help plants grow. However, using too much, especially phosphate fertilizers or NPK, can reduce the soil's natural fertility over time.
2. **Pesticides:** These chemicals kill unwanted pests or weeds. This group includes insecticides (like DDT, BHC, aldrin), fungicides (like organo mercury compounds), and herbicides (like sodium chlorate). These substances can stay in the soil for a long time, get absorbed by crops, and are harmful to living beings, including mammals.
3. **Industrial Wastes:** Factories and mining activities release many toxic materials into the soil. These include cyanides, chromates, acids, alkalis, and heavy metals like mercury, copper, zinc, cadmium, and lead. These wastes remain in the soil, making it unsuitable for use for a very long time.
4. **Sediments:** Soil erosion caused by farming and mining can lead to sediments polluting the soil, changing its composition and health.
5. **Radioactive Substances:** Mining for uranium and other minerals releases radioactive materials, which are dangerous pollutants.
6. **Heat:** Water used to cool machinery in industries, when discharged, can change the soil temperature and affect soil organisms.
In simple words: Soil pollution is caused by things like too much fertilizer, harmful chemicals used to kill pests, waste from factories, soil washing away, radioactive materials, and warm water from industries. These make the soil unhealthy and affect living things.

🎯 Exam Tip: Remember to list both chemical and physical sources of soil pollution and provide specific examples for each category to score full marks.

 

Question 7. Explain the various contribution of green chemistry in our day to day life.
Answer: Green chemistry focuses on creating chemical products and processes that are safer and better for the environment. It helps in our daily lives in several ways:
1. **Dry Cleaning Clothes:** Traditionally, dry cleaning used tetrachloroethylene, which polluted groundwater and was harmful. Green chemistry introduced liquefied carbon dioxide with suitable detergents as a safer alternative, which is not harmful to groundwater. Also, hydrogen peroxide (\(H_2O_2\)) is now used for bleaching clothes, providing better results while using less water.
2. **Bleaching Paper:** In the past, chlorine was used to bleach paper. Now, hydrogen peroxide (\(H_2O_2\)) with a catalyst can be used, making the process cleaner.
3. **Making Chemicals:** Acetaldehyde is an important chemical. Green chemistry allows it to be made by reacting ethene with oxygen using a special ionic catalyst in water, resulting in a high yield of 90%.
\(CH_2 = CH_2 + O \xrightarrow{\text{Catalyst Pd(II) / Cu (II)}} CH_3CHO\)
This method is more efficient and creates less waste.
4. **Fuel for Cars:** Methanol is now considered a cheaper and cleaner alternative to petrol for automobiles. When burned, methanol offers higher thermal efficiency and power, with less heat vaporization, making it better for the environment.
5. **Safer Pesticides:** Green chemistry has developed neem-based pesticides. These are much safer than older types like chlorinated hydrocarbons, which were more harmful to the environment. Every person plays a role in protecting our environment.
In simple words: Green chemistry helps us in daily life by making processes like dry cleaning and paper bleaching safer. It also helps make chemicals more efficiently and provides cleaner fuels for cars. It even gives us safer bug sprays from plants, all while being kinder to Earth.

🎯 Exam Tip: When explaining green chemistry contributions, highlight both the traditional harmful method and the new environmentally friendly solution provided by green chemistry, along with a concise explanation of the benefit.