NCERT Solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry- In this chapter, we will focus on environmental chemistry. Environmental chemistry plays a major role in our environment. Various chemical species present in the environment which are either naturally occurring or either generated by human activities. This is an important chapter for a chemistry student. There is a total of 20 questions in the exercise. The NCERT solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry are prepared and designed by subject experts. These NCERT solutions help students in their preparation of CBSE class 11 final examination and also help in various competitive exams like NEET, JEE Main etc. In this chapter, we will discuss NCERT solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry along with environmental pollution related to the water, soil and air, cause of smog, depletion of the ozone layer, global warming, greenhouse effect etc. The NCERT solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry will help students to strengthen their concepts because this is a theoritical chapter and many theroitical concepts will be learnt directly through these solutions. By referring to the NCERT solutions for class 11 , students can understand all the important concepts and practice questions well enough before their examination
NCERT Class 11 Chemistry Chapter 14 Environmental Chemistry starts with two important lines "The world has achieved brilliance without wisdom, power without conscience. Ours is a world of nuclear giants and ethical infants". Environmental studies deal with the sum of all biological, physical, chemical, economical and social interrelations with our surroundings. After completing this chapter with the help of NCERT solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry , students will be able to define atmospheric pollution, and list reasons for the water pollution, soil pollution, greenhouse effect, global warming and acid rain; able to identify causes of the ozone layer and what is its effects on the environment and appreciate the importance of green chemistry in our daily life.
What is Environmental chemistry?
Environmental chemistry is a branch of chemistry which deals with the transport reactions, chemical change, effects and fates of chemical species in the environment. It has three main components:- Abiotic (non-living thing), Biotic (living things) and Energy component. According to environmental studies, as a human being, it's our responsibility to protect our environment.
Important points of Class 11 Chemistry Chapter 14 Environmental Chemistry-
- Pollution is the effect of undesirable changes in the environment, resulting in harmful effects on human beings, animals and plants.
- Pollutants exist in all three states-solid, liquid, and gaseous state.
- Atmospheric pollution generally studies as tropospheric pollution and stratospheric pollution. The troposphere extends up to the height of ~10 Km from the sea level. And stratosphere extends above troposphere up to the 50 km.
- One of the important constituents of the stratosphere is the ozone layer.
- BOD(Biological oxygen demand)- the amount of dissolved oxygen needed by bacteria to break down the organic material present in a certain volume in the water sample. For clean water, the BOD value is less than 5ppm whereas highly polluted water could have a BOD value of 17 ppm or more.
Topics of NCERT Grade 11 Chemistry Chapter 14 Environmental Chemistry
14.1 Environmental Pollution
14.2 Atmospheric Pollution
14.3 Water Pollution
14.4 Soil Pollution
14.5 Industrial Waste
14.6 Strategies to control Environmental Pollution
14.7 Green Chemistry
NCERT Solutions for Class 11 Chemistry Chapter 14 Environmental Chemistry- Exercise Questions
Question 14.1. Define environmental chemistry.
It is a branch of chemistry which deals with the chemical change, transport reactions, effects and fates of chemical species in the environment. It has three main components:-
- Abiotic (non-living thing)
- Biotic(living things)
- Energy component
Question 14.2. Explain tropospheric pollution in 100 words.
Tropospheric pollution, the main cause of this pollution is due to the presence of undesirable substances such as solid or gaseous particles in the lowest layer of the atmosphere.
Major pollutants present in the troposphere-
- Gaseous Pollutants-These is mainly, the oxides of the sulphur( ), nitrogen and carbon, hydrogen sulphide( ), hydrocarbons, ozone and other oxidants.
- Particulate pollutants- Dust, mist, fumes and smog etc are the main constituents.
Oxides of sulphur and nitrogen are produced by the burning of fossil fuels like coal and automobile fuel and when these gases react with the water to form nitric acid ( ) and sulphuric acid, as a result, acid rain is formed.
Acid rain causes harm to plants, trees, and agriculture. It also leads to respiratory problem.
When we burn hydrocarbons (contains hydrogen and carbon) they produce the oxides of carbon. Hydrocarbons are carcinogenic in nature and so that their products are also major pollutants. Carbon monoxide ( ), produced from incomplete combustion of carbon. It has the ability to block the delivery of oxygen to the organs and tissues. Though carbon dioxide is not toxic in nature, it contributes towards global warming by trapping the reflected IR rays.
Particulates of smoke, mist, dust and fumes are harmful to us because they can block our nasal passage and cause many respiratory ailments.
Question 14.3. Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
Yes, carbon monoxide is more poisonous than carbon dioxide, (non-toxic in nature). has the ability to block delivery of oxygen to the organ and tissue. Also, it binds to haemoglobin to form a complex carboxyhaemoglobin, which is 300 times more stable than the oxygen-haemoglobin complex.
If the concentration of these complex reaches 3-4% then the capacity of blood to carry oxygen is reduced.
On the other hand, is not poisonous, it is harmful only at high concentration.
Question 14.5. Statues and monuments in India are affected by acid rain. How?
Oxide of sulphur and nitrogen reacts with water in the presence of dioxygen( ), as a result, acid rain is formed.
Acid rain cause damages to the buildings and structures made of stone and marble and metals. In India, for the construction of monuments and statues, we use limestone, including Taj Mahal.
Acid rain on reacting with limestone decolourise the surface of the stone also their lustre.
The reaction between limestone and acid rain-
Question 14.6. What is smog? How is classical smog different from photochemical smogs?
Smog is a mixture of smoke and fog. It is the pollutants of air pollution. It affects our eyesight during the winter. There are two types of smog-
- Classical smog - It occurs in a cool, humid climate. It is reducing in nature and it has smoke, fog and sulphur dioxide.
- photochemical smog- It occurs in a dry and sunny climate. It is oxidising in nature and its components are PAN, ozone and nitric oxide etc.
Question 14.7. Write down the reactions involved during the formation of photochemical smog.
Following reaction are involved during the formation of photochemical smog-
It is formed by the reaction of sunlight with hydrocarbons and nitrogen oxides. Burning of hydrocarbons leads to release of nitrogen oxide in the atmosphere and high concentration of these pollutants, a chain reaction by the interaction with sunlight.
Oxygen atoms are very reactive and combine with the dioxygen to produce ozone.
It rapidly reacts with NO, formed in the first reaction and regenerate (g)
Both and ozone are oxidising in nature so they react with the unburnt hydrocarbon in the air to form PAN, formaldehyde and acrolein.
Question 14.8. What are the harmful effects of photochemical smog and how can they be controlled?
Harmful effects of photochemical smog-
- Because of their oxidising nature, and , causing corrosion of metals, stone, rubber and painted surface.
- Ozone and nitric acid are eye irritants, the nose and throat and due to the high concentration of these causes headache, chest pain, and difficulty in breathing.
- by controlling the primary precursors, such as and hydrocarbons, secondary precursors will be automatically reduced.
- Use of catalytic converters is used in the automobiles, which prevent the release of nitrogen oxide and hydrocarbons to the atmosphere.
plantation of certain plants such as Pinus, Juniperus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide
Question 14.9 . What are the reactions involved for ozone layer depletion in the stratosphere?
In the stratosphere, when UV radiation acting on dioxygen ( ), the ozone molecule is formed. The UV rays split the dioxygen into free oxygen.
Once CFCs are released in the atmospheric gases and reach the stratosphere, they get broken down by UV radiation.
Then chlorine radical reacts with an ozone molecule to form chlorine monoxide radicals-
Question 14.10. What do you mean by ozone hole? What are its consequences?
The depletion of the ozone layer due to the chlorine-free radical , which is continuously regenerated at the stratosphere. This phenomenon is known as the ozone hole.
Effects of depletion of the ozone layer-
- With the depletion of the ozone layer, more amount of the UV radiation will enter the earth's atmosphere.
- UV radiations are harmful to us because they lead to skin damage, ageing of the skin, cataract, skin cancers and sunburns.
- It increases the evaporation of surface water through the stomata of the leaves and reduces the moisture content from the soil.
- Plants proteins are also affected by UV radiation, which leads to the mutation of cells.
Question 14.11. What are the major causes of water pollution? Explain.
The major cause of water pollutions are -
- Radioactive waste - These waste substances are direct throw into the oceans.
- Pathogens - include bacteria and other organisms, which enters into the water from animal excreta and domestic sewage. Also, human excreta contain bacterias like Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases
- Organic Wastes - These are biodegradable waste that pollutes water as a consequence of runoff. The excess of organic matter in water causes a decrease in the amount of oxygen held by the water.
- Chemical pollutants - water-soluble inorganic chemicals such as heavy metals like cadmium, mercury, nickel etc. The presence of these metals in the human body, damages the kidneys, central nervous system, liver etc. These are dangerous for human beings because our body cannot excrete them.
Question 14.12. Have you ever observed any water pollution in your area? What measures would you suggest to control it?
Following measurements should be taken to avoid water pollution-
- Industrial and chemical discharges should be made free from all the toxic metals before throwing them into water bodies.
- The concentration of these heavy metals should be checked regularly.
- Compost should be prefered instead of using chemical fertilizers in agricultural fields to prevent the toxic chemical from entering groundwater.
Question 14.13. What do you mean by Biochemical Oxygen Demand (BOD)?
Biochemical Oxygen Demand (BOD)
It is the amount of oxygen required by bacteria to decompose the organic matter present in a certain volume of the sample of water. Clean water would have a BOD value less than 5 ppm and highly polluted water could have a BOD value of 17 ppm.
Question 14.14. Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?
Mostly, soil pollution is due to the industrial wastes and agricultural pollutants such as herbicides, pesticide and fertilisers etc.
Pesticide like DDT is not soluble in water so that they remain in the soil for a very long period, causing the contamination of roots of crops. Aldrin and DIeldrin are non-biodegradable pesticides and highly toxic.
A suitable way for controlling the soil pollution is to avoid the direct addition of pollutants to the soil And also wastes should undergo proper treatment. They should be first recycled and only then, allowed to dump.
Question 14.15. What are pesticides and herbicides? Explain giving examples.
A pesticide is used to kill pests, including insects, plant pathogens etc It is a mixture of two or more substance. Aldrin and Dieldrin are common pesticides. Herbicides are used to kill the weeds. for example sodium chlorate ( ), sodium arsenite ( ).
Question 14.16. What do you mean by green chemistry? How will it help decrease environmental pollution?
Green chemistry is a way of thinking, by utilising the existing knowledge and principles of chemistry and other methods to reduce the adverse impact on the environment. Green chemistry is a production process which brings minimum pollution to the environment. In this, the chemical reactants are, which give 100% end products.
Question 14.19. How can domestic waste be used as manure?
According to the nature of the waste material. It can be divided into two categories one is bio-degradable, and the other is non-bio degradable. For example, leaves, papers, rotten food etc. are under the type of biodegradable waste. These should be deposited in the landfills, where they can get decomposed by the bacteria anaerobically into manure. And non-biodegradable waste is sent for recycling.
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