Welcome to Swastik Classes’ comprehensive NCERT Solutions for Class 11 Chemistry Chapter 14 – Environmental Chemistry. In this chapter, we delve into the fascinating world of environmental chemistry, where we explore the intricate relationship between chemical processes and the environment.
Environmental chemistry plays a crucial role in understanding the impact of human activities on the Earth’s ecosystem and finding sustainable solutions to environmental challenges. Through this collection of meticulously crafted solutions, Swastik Classes aims to provide students with a deeper understanding of the concepts covered in the NCERT textbook.
Our expert team of educators has carefully prepared these solutions to assist students in comprehending the fundamental principles and theories of environmental chemistry. Each solution is presented in a concise and organized manner, ensuring clarity and facilitating effective learning.
With our NCERT Solutions, students will gain a comprehensive understanding of topics such as environmental pollution, the greenhouse effect, ozone depletion, and various measures to combat environmental degradation. The step-by-step explanations, along with relevant diagrams and examples, will help students grasp the concepts with ease.
Moreover, the solutions provided by Swastik Classes encourage critical thinking and problem-solving skills, enabling students to tackle complex environmental issues. We believe that a solid foundation in environmental chemistry is vital for creating environmentally conscious citizens who can actively contribute to a sustainable future.
Whether you are preparing for your exams or simply striving to enhance your knowledge in the field of environmental chemistry, Swastik Classes’ NCERT Solutions for Class 11 Chemistry Chapter 14 will serve as your ultimate guide. Let us embark on this enriching journey together and explore the fascinating realm of environmental chemistry.
NCERT SOLUTIONS FOR CLASS 11 CHEMISTRY CHAPTER 14- ENVIRONMENTAL CHEMISTRY – Exercises
Chapter-14 Environmental Chemistry
Answer the following Questions.
1. Define environmental chemistry.
Answer: Environmental chemistry is the study of chemical and biochemical processes occurring in nature. It deals with the study of origin, transport, reaction, effects, and fates of various chemical species in the environment.
2. Explain tropospheric pollution in 100 words.
Answer: Tropospheric pollution arises due to the presence of undesirable substances in the lowest layer of the atmosphere.
Oxides of sulphur, nitrogen, carbon, and hydrocarbons are the major gaseous pollutants.
Oxides of sulphur (SO2 and SO3) and nitrogen (NO2, NO) are produced as a result of burning of fossil fuels (coal, automobile fuel). These oxides react with water in the presence of atmospheric oxygen to form nitric acid (HNO3) and sulphuric acid (H2SO4), which leads to the formation of ‘Acid rain’.
Acid rain causes harm to agriculture, plants, and trees. It also leads to various respiratory ailments.
Hydrocarbons are carbon and hydrogen containing compounds that burn to produce oxides of carbon. Hydrocarbons are carcinogenic and their products are also major pollutants. Carbon monoxide (CO) is poisonous in nature as it reacts with the haemoglobin of blood, which can even result in death. Though carbon dioxide (CO2) is not toxic in nature, yet it contributes towards global warming by trapping the reflected IR rays. This results in the heating up of the Earth’s atmosphere, thereby leading to the melting of icebergs and glaciers.
Particulates of smoke, dust, mist, and fume are harmful for human health as they are likely to block the nasal passage of a person, causing respiratory ailments. Smoke and fog combine to produce smog during a cool, humid day, thereby reducing visibility to a large extent. Photochemical smog is formed due to the presence of PAN, ozone, formaldehyde, and acrolein. It causes eye irritation, headaches, and chest pain. It also leads to the cracking of rubber and does damage to plants.
3. Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
Answer: Carbon dioxide (CO2) and carbon monoxide (CO) gases are emitted during the combustion of various fuels. Carbon monoxide is poisonous, whereas carbon-dioxide is non-toxic in nature.
Carbon monoxide is poisonous because it is capable of forming a complex with haemoglobin (carboxy haemoglobin), which is more stable than the oxygen-haemoglobin complex. The concentration range of 3–4% of carboxy haemoglobin decreases the oxygen-carrying capacity of blood. This results in headaches, weak eyesight, nervousness, and cardiovascular disorders. A more increased concentration may even lead to death.
Carbon dioxide is not poisonous. It proves harmful only at very high concentrations.
4. List gases which are responsible for greenhouse effect.
Answer:
The major greenhouse gases are:
1) Carbon dioxide (CO2)
2) Methane (CH4)
3) Water (H2O)
4) Nitrous oxide (NO)
5) Ozone (O3)
6) Chlorofluorocarbons (CFCs)
5. Statues and monuments in India are affected by acid rain. How?
Answer: Acid rain is a byproduct of various human activities that leads to the emission of oxides of sulphur and nitrogen in the atmosphere. These oxides undergo oxidation and then react with water vapour to form acids.
Acid rain causes damage to buildings and structures made of stone and metal. In India, limestone is a major stone used in the construction of various monuments and statues, including the Taj Mahal.
Acid rain reacts with limestone as:
This results in the loss of lustre and colour of monuments, leading to their disfiguration.
6. What is smog? How is classical smog different from photochemical smog?
Answer:
Smog is a kind of air pollution. It is the blend of smoke and fog. There are two kinds of smog:
a) Classical smog
b) Photochemical smog
The two smogs can be differentiated as follows:
| Classical smog | Photochemical smog | |
| Occurrence | It occurs in a cool, humid climate. | It occurs in a dry, sunny climate. |
| Components | Smoke, fog, and sulphurdioxide. | PAN, acrolein, ozone, formaldehyde, nitric oxide. |
| Nature | It is reducing in nature | It is oxidizing in nature. |
7. Write down the reactions involved during the formation of photochemical smog.
Answer: Photochemical smog is formed as a result of the reaction of sunlight with hydrocarbons and nitrogen oxides. Ozone, nitric oxide, acrolein, formaldehyde, and peroxyacetyl nitrate (PAN) are common components of photochemical smog. The formation of photochemical smog can be summarized as follows:
Burning of fossil fuels leads to the emission of hydrocarbons and nitrogen dioxide in the atmosphere. High concentrations of these pollutants in air results in their interaction with sunlight as follows:
While ozone is toxic in nature, both NO2 and O3 are oxidizing agents. They react with the unburnt hydrocarbons in air to produce formaldehyde, PAN, and acrolein.
8. What are the harmful effects of photochemical smog and how can they be controlled?
Answer:
EFFECTS OF PHOTOCHEMICAL SMOG:
Photochemical smog is oxidizing smog owing to the presence of NO2 and O3, causing corrosion of metals, stones, rubber, and painted surfaces. The other major components of photochemical smog are PAN, acrolein, and formaldehyde. Both PAN and ozone are eye irritants, while nitric oxide (formed from NO2) causes nose and throat irritation. At higher concentrations, photochemical smog causes chest pain, headaches, throat dryness, and various respiratory ailments.
CONTROL MEASURES:
Photochemical smog results from the burring of fossil fuels and automobile fuels that emit NO2 and hydrocarbons, which in turn form ozone, PAN, and other chemicals. The use of catalytic converters in automobiles is recommended to prevent the release of NO2 and hydrocarbons into the atmosphere.
Plantation of plants such as Pinus, Juniparur, Quercus, Pyrus, and Vitis is also advised as these plants have the capability to metabolize NO2.
9. What are the reactions involved for ozone layer depletion in the stratosphere?
Answer:
In the stratosphere, ozone is a product of the action of UV radiations on dioxygen as:
(i)
(ii)
Reaction (ii) indicates the dynamic equilibrium existing between the production and decomposition of ozone molecules. Any factor that disturbs the equilibrium may cause depletion of ozone layer by its decomposition. One such factor is the release of chlorofluorocarbon compounds (CFCs). These are non-reactive, non-flammable molecules that are used in refrigerators, air conditioners, plastics, and electronic industries.
Once released CFCs mix with atmospheric gases and reach the stratosphere, where they are decomposed by UV radiations.
(iii)
The chlorine free radical produced in reaction (iii) reacts with ozone as:
(iv)
The 
radicals further react with atomic oxygen to produce more chlorine radicals as:
(v)
The regeneration of 
10. What do you mean by ozone hole? What are its consequences?
Answer: In Polar regions, stratospheric clouds provide the surface for chlorine nitrate and hypochlorous acid, which react further to give molecular chlorine. Molecular chlorine and HOCl are photolysed to give chlorine-free radicals.
The chlorine-free radicals lead to the decomposition of ozone as:
Hence, a chain reaction is initiated. The chlorine-free radical is continuously regenerated, thereby depleting the ozone layer. This phenomenon is known as the as ‘ozone hole’.
Effects of depletion of ozone layer
The ozone layer protects the Earth from the harmful UV radiations of the sun. With the depletion of the layer, more radiation will enter the Earth’s atmosphere. UV radiations are harmful because they lead to the ageing of skin, cataract, skin cancer, and sunburns. They cause death of many phytoplanktons, which leads to a decrease of fish productivity. Excess exposure may even cause mutation in plants.
Increase in UV radiations, decreases the moisture content of the soil and damages both plants and fibres.
11. What are the major causes of water pollution? Explain.
Answer: Water pollution arises as a result of several human activities, which leads to the presence of several undesirable substances in water.
Major water pollutants with their sources have been tabulated as follows:
| Pollutant | Source |
| Micro-organisms | Domestic sewage |
| Organic wastes | Domestic sewage, decaying animals and plants, animal excreta and waste, discharge from food processing industries |
| Plant nutrients | Chemical fertilizers |
| Toxic heavy metals | Chemical factories and industries |
| Sediments | Strip mining and soil erosion |
| Pesticides | Chemicals used for killing fungi, weed, insects |
| Radioactive substances | Mining of uranium-containing minerals |
| Heat | Water used for cooling in industries |
Roles played by major pollutants are:
1. Pathogens: These water pollutants include bacteria and other organisms. They enter water from animal excreta and domestic sewage. Bacteria present in human excreta (for example, Escherichia coli and Streptococcus faecalis) cause gastrointestinal diseases.
2. Organic wastes: These are biodegradable wastes that pollute water as a result of run off. The presence of excess organic wastes in water decreases the amount of oxygen held by water. This decrease in the amount of dissolved oxygen inhibits aquatic life.
3. Chemical pollutants: These are water soluble chemicals like heavy metals such as cadmium, mercury, nickel, etc. The presence of these chemicals (above the tolerance limit) can damage the kidneys, central nervous system, and liver.
12. Have you ever observed any water pollution in your area? What measures would you suggest to control it?
Answer: Water pollution arises as a result of various human activities. This includes discharges from wastewater treatment plants, run-off from agricultural fields, storm-water drainage, etc. Pollutants from these sources enter the water bodies, thereby contaminating the water and rendering it impure.
Industries and chemical factories discharge toxic, heavy metals such as Fe, Mn, Al, etc., along with organic wastes into water. Domestic sewage and animal excreta are also responsible for pathogenic contamination of water. These pollutants make water unfit for drinking.
Therefore, all industrial and chemical discharges should be made free from toxic metals before allowing them to enter a water body. The concentration of these pollutants should be checked regularly. Compost should be preferred over chemical fertilizers in gardens and agricultural fields to avoid harmful chemicals from entering ground water.
13. What do you mean by Biochemical Oxygen Demand (BOD)?
Answer: Biochemical oxygen demand is the amount of oxygen required by bacteria to decompose organic matter in a certain volume of sample of water. Clean water would have a BOD value of less than 5 ppm, whereas highly polluted water has a BOD value of 17 ppm or more.
14. Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?
Answer: Major sources of soil pollution are industrial wastes and agricultural pollutants such as pesticides, fertilizers, etc.
It is very important to maintain the quality and fertility of soil to ensure and sustain the growth of plants and food crops.
Insecticides like DDT are not soluble in water. For this reason, they remain in soil for a long time, contaminating the root crops. Pesticides like Aldrin and Dieldrin are non-biodegradable and highly toxic in nature. They can enter the higher trophic levels through food chains, causing metabolic and physiological disorders. The same is true for industrial wastes that comprises of several toxic metals like Pb, As, Hg, Cd, etc.
Hence, the best way to check soil pollution is to avoid direct addition of pollutants to the soil. Also, wastes should undergo proper treatment. They should be recycled and only then, allowed to be dumped.
15. What are pesticides and herbicides? Explain giving examples.
Answer: Pesticides are a mixture of two or more substances. They are used for killing pests. Pests include insects, plant pathogens, weeds, mollusks, etc., that destroy the plant crop and spread diseases. Aldrin and dieldrin are the names of some common pesticides
Herbicides are pesticides specially meant for killing weeds. For example, sodium chlorate (NAClO3), sodium arsenite (Na3 AsO3), etc.
16. What do you mean by green chemistry? How will it help decrease environmental pollution?
Answer: Green chemistry is a production process that aims at using the existing knowledge and principles of chemistry for developing and implementing chemical products and processes to reduce the use and generation of substances hazardous to the environment
The release of different harmful chemicals (particulates, gases, organic and inorganic wastes) causes environmental pollution. In green chemistry, the reactants to be used in chemical reactions are chosen in such a way that the yield of the end products is up to 100%. This prevents or limits chemical pollutants from being introduced into the environment. Through the efforts of green chemists, H2O2 has replaced tetrachlorethane and chlorine gas in drying and bleaching of paper.
17. What would have happened if the greenhouse gases were totally missing in the earth’s atmosphere? Discuss.
Answer: Earth’s most abundant greenhouse gases are CO2, CH4, O3, CFCs, and water vapour. These gases are present near the Earth’s surface. They absorb solar energy that is radiated back from the surface of the Earth. The absorption of radiation results in the heating up of the atmosphere. Hence, greenhouse gases are essential for maintaining the temperature of the Earth for the sustenance of life.
In the absence of greenhouse gases, the average temperature of the Earth will decrease drastically, making it uninhabitable. As a result, life on Earth would be impossible.
18. A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.
Answer: The amount of dissolved oxygen present in water is limited. The abundance of phytoplanktons causes depletion of this dissolved oxygen. This is because, phytoplanktons are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. Hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish-kill.
19. How can domestic waste be used as manure?
Answer: Depending upon the nature of the waste, domestic waste can be segregated into two categories i.e., biode gradable and non–biode gradable. Biode gradable waste such as leaves, rotten food, etc. should be deposited in land fills, where they get decomposed aerobically and anaerobically into manure. Non-biode gradable waste (which cannot be degraded) such as plastic, glass, metal scraps etc. should be sent for recycling.
20. For your agricultural field or garden you have developed a compost producing pit. Discuss the process in the light of bad odour, flies and recycling of wastes for a good produce.
Answer: It is essential to take proper care of the compost producing pit in order to protect ourselves from bad odour and flies.
It should be kept covered to minimize bad odour and prevent flies from entering it.
The recyclable waste should not be dumped in the compost producing pit. It should be sent to the industries through vendors for recycling.
Conclusions for NCERT SOLUTIONS FOR CLASS 11 CHEMISTRY CHAPTER 14- ENVIRONMENTAL CHEMISTRY
Swastik Classes’ NCERT Solutions for Class 11 Chemistry Chapter 14 – Environmental Chemistry offer a comprehensive and well-structured resource for students. Our solutions not only cover the essential topics but also provide a deep understanding of the intricate relationship between chemistry and the environment.
By studying these solutions, students will gain a solid foundation in environmental chemistry and develop a critical understanding of the environmental challenges we face today. They will learn about the causes and effects of environmental pollution, the mechanisms behind global warming and ozone depletion, and the measures taken to mitigate environmental degradation.
The step-by-step explanations, diagrams, and examples provided in our solutions ensure clarity and facilitate effective learning. Our expert team of educators has taken great care in crafting these solutions to address the specific needs of Class 11 students, enabling them to grasp the concepts with ease.
Moreover, our solutions encourage critical thinking and problem-solving skills, empowering students to analyze environmental issues and propose sustainable solutions. By studying environmental chemistry, students will not only gain knowledge but also develop a sense of responsibility towards the environment, becoming active contributors to a sustainable future.
Swastik Classes is committed to providing high-quality educational resources, and our NCERT Solutions for Class 11 Chemistry Chapter 14 exemplify that commitment. We hope that these solutions serve as a valuable tool for students in their academic journey and inspire them to make a positive impact on the environment.
Embark on this enriching journey with Swastik Classes and let us together explore the fascinating world of environmental chemistry, working towards a greener and healthier planet for generations to come.
Q1: Why is environmental chemistry important?
A1: Environmental chemistry is important because it helps us understand the impact of chemical processes on the environment. It allows us to study and analyze environmental pollution, climate change, ozone depletion, and other environmental issues. By studying environmental chemistry, we can develop sustainable solutions to mitigate these problems and work towards a cleaner and healthier planet.
Q2: How can NCERT Solutions for Class 11 Chemistry Chapter 14 help me?
A2: NCERT Solutions for Class 11 Chemistry Chapter 14 provide comprehensive and well-structured answers to the questions and exercises given in the NCERT textbook. These solutions help you understand the concepts covered in the chapter, such as environmental pollution, greenhouse effect, ozone depletion, and more. They also provide step-by-step explanations, diagrams, and examples, making it easier for you to grasp the concepts and score well in your exams.
Q3: What are some major sources of environmental pollution?
A3: Some major sources of environmental pollution include industrial emissions, vehicle exhaust, burning of fossil fuels, improper waste disposal, deforestation, and agricultural practices. These activities release pollutants such as greenhouse gases, particulate matter, volatile organic compounds (VOCs), and heavy metals into the environment, leading to air, water, and soil pollution.
Q4: What is the greenhouse effect?
A4: The greenhouse effect refers to the process by which certain gases in the Earth’s atmosphere, such as carbon dioxide (CO2) and methane (CH4), trap heat radiated from the Earth’s surface. These gases allow sunlight to pass through but absorb and re-emit the infrared radiation, causing a warming effect on the planet. While the greenhouse effect is natural and necessary to sustain life, human activities have intensified it, leading to global warming and climate change.
Q5: How does ozone depletion occur, and what are its consequences?
A5: Ozone depletion occurs due to the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS) into the atmosphere. These substances break down ozone (O3) molecules in the stratosphere, resulting in the thinning of the ozone layer. The consequences of ozone depletion include increased ultraviolet (UV) radiation reaching the Earth’s surface, which can lead to skin cancer, eye damage, suppression of immune systems, and harmful effects on marine ecosystems and agriculture.
