Environmental Chemistry Class 11 Notes CBSE Chemistry Chapter 14 (Free PDF Download)

Section – A (1 Mark Questions)

1. Define Troposphere?

Ans. The lowest region atmosphere in which the human beings along with other organisms live is called troposphere. It extends upto the height of -10 km form sea level.

2. Give some name of gaseous air pollutants.

Ans. Gaseous air pollutants are oxides of sulphur, nitrogen carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.

3. Explain the diseases caused by sulphur dioxide?

Ans. Sulphur dioxide causes respiratory diseases eg. Asthma, bronchitis, emphysema in human beings, sulphur dioxide causes irritation to the eyes, resulting in tears and redness.

4. Green house effect is caused by which gases? List some names.

Ans. Carbon dioxide, methane, water vapors, nitrous oxide, CFC’s and ozone are responsible for green house effect.

5. What happens when CFCs come in contact with ozone layer?

Ans. Chlorofluorocarbon (CFC’s) damage the ozone layer and creates holes in ozone layer.

6. Describe greenhouse effect?

Ans. Atmosphere traps the Sun’s heat near the Earth’s surface and keeps it warm. This is Greenhouse effect.

7. Disease  caused due to ozone layer depletion?

Ans. Ultraviolet rays reaching the earth passing through the ozone hole cause skin cancer.

8. Define smog?

Ans. When smoke mix with fog, it is called smog.

9. List two names of gases which cause acid rain.

Ans. NO2 and SO2.

10. In which season London smog is caused and time of the day?

Ans. The London smog is caused during summer season and in the afternoon part of the day when it is very hot.

Section – B (2 Marks Questions)

11. Photochemical smog is composed of what?

Ans. Photochemical smog is formed as a result of photochemical reaction (i.e., in the presence of sunlight) between oxides of nitrogen and hydrocarbons.

12. The maximum and minimum BOD value for pure water and polluted water respectively.

Ans. The amount of BOD in water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have BOD value of less than 5 ppm whereas highly polluted water would have a BOD value of 17 ppm or more.

13. Role of ozone layer in the stratosphere?

Ans. The presence of ozone in the stratosphere prevents about 99.5% of the sun’s harmful ultraviolet (uv) radiations from reaching the earth’s surface and thereby protecting humans and other animals from its effect.

14. Define Stratosphere pollutants  ? Give examples.

Ans. Depletion of ozone layer in stratospheres leading to reach harmful UV radiation on earth is the result of stratospheric pollution. The presence of chloro fluoro carbon compounds in the atmosphere is responsible for this depletion.

15. Carbon dioxide is highly poisonous, State reason.

Ans. Carbon monoxide binds to hemoglobin to form carboxyl-haemoglobin, which is about 300 times more stable than the oxygen – haemoglobin complex. In blood when the concentration of carboxyl hemoglobin is greatly reduced. This oxygen deficiency, results into headache, weak eyesight, nervousness and cardiovascular disorder.

16. Hydrocarbons is not good for human beings as well as plants?

Ans. Hydrocarbons are carcinogenic i.e., they cause cancer. They harm plants by causing ageing, breakdown of tissues and shedding of leaves flowers and trigs.

17. Which zone is called ozonosphere?

Ans. Stratosphere zone is called ozonosphere.

18. Discuss ‘greenhouse effect’? And its effects on the global climate?

Ans. The warming of the earth or global warming due to re-emission of sun’s energy absorbed by the earth followed by its absorption by CO2 molecules and H2O vapours present in the atmosphere, near the earth’s surface and then its radiation back to the earth is called greenhouse effect.

19. Describe pneumoconiosis?

Ans. The smaller particulate pollutants are more likely to penetrate into the lungs. These five particles are carcinogens Inhalation of small particles irritates the lung and exposure to such particles for long period of time causes fibrosis of the lung lining. These type of disease is termed as pneumoconiosis.

20. List some preventive measures for photochemical smog?

Ans. If we control the primary precursors of photochemical smog such as NO2 and hydrocarbons, the secondary precursors such as ozone and PAN, the photochemical smog will automatically be reduced. Usually catalytic converters are used in the automobiles which prevent the release of nitrogen oxide and hydrocarbon to the atmosphere. Certain plants eg. Pines, Juniparus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide and their plantation could help in this matter.

PDF Summary - Class 11 Chemistry Environmental Chemistry Notes (Chapter 14)

1. The environment encompasses the air, water, soil, plants, and atmosphere in which we live.

2. Environmental chemistry is the discipline of chemistry that deals with the interaction between living organisms and their surroundings.

3. Pollution Effects: 

1. Nearly 3000-4000 individuals perished as a result of the London Smog.

2. Many people in Japan have contracted "Minamata," a sickness caused by mercury contamination in the waters of Minamata Island, which spread after people ate fish caught there.

3. In 1984, a gas called methyl isocyanate (MIC) spilled from a union carbide factory in Bhopal, killing thousands of people.

4. Acid rain is destroying many buildings in Italy, particularly in Rome.

5. The Mediterranean Sea, which has become a "dead sea," is no longer capable of supporting aquatic life.

6. The sacred river Ganges in India has been purified by a special board.

7. Dangerous radiations emitted by radioactive fallout from reactors and nuclear weapons testing cause air pollution.

8. Air pollution is reducing the Taj Mahal's beauty.

9. Thousands of people died in the Japanese cities of Hiroshima and Nagasaki as a result of the atomic bomb during World War II.

10. The population of Chernobyl, Russia, were more affected by nuclear pollution.

11. An accident at HPCL's oil refinery in Visakhapatnam.

12. In Indonesia, an unintentional forest fire did extensive damage to the environment.

4. Definition of Term:

a. Pollutant: 

A pollutant is a substance found in nature that has grown in amount as a result of human activities and has a negative impact on the environment. For example, carbon dioxide, sulpur dioxide, lead in mercury, and so on.

b. Contaminant: 

A contaminant is a chemical that is not found in nature but is discharged as a result of human activities and harms the environment. For example, in Bhopal, the lethal gas methyl isocyanate (MIC) seeped from the union carbide factory.

c. Receptor: 

A receptor is a medium that is affected by pollutants.

d. Sink: 

A sink is a medium that reacts with the pollutant and reduces pollution's impact.

1. Microorganisms that consume dead animals or turn dry leaves and rubbish into fertilizers.

2. Seawater is a large carbon dioxide sink. Plants are also excellent $\mathrm{CO}_{2}$ sinks.                                                                                                                       

• Speciation is the classification of diverse contaminants according to their degree of toxicity.   

• Mercury is less hazardous than alkylated mercury. Mercury compounds are toxic in comparison to lead.

e. Oxygen Dissolved (D.O.)

1. Dissolved oxygen (D.O.) is the amount of oxygen contained in water in a dissolved state.

2. In water, the amount of oxygen required for healthy plant and animal growth is $4-6 \mathrm{mg} \mathrm{L}^{-1}$ 

3. When the D.O. value in waterfalls below 5 ppm, the water is considered contaminated.    

The higher the DO value, the lower is the pollution of water and vice versa.

4. As the temperature rises, the D.O. value falls.

f. B.O.D. (Biochemical Oxygen Demand)

1. The amount of oxygen required by bacteria and other microorganisms while decomposing organic matter under aerobic (oxygen present) conditions at a specific temperature is referred to as biochemical oxygen demand (BOD).

2. The B.O.D. the value for clean water is 3 ppm.

3. Impure water has a greater B.O.D. value (>3 ppm) than pure water.

4. The BOD value of municipal sewage ranges from 100 to 4000 ppm.

5. Higher BOD levels in water cause plant, fish, and aquatic species to die.

g. COD (Chemical Oxygen Demand):

1. The chemical oxygen demand (COD) is a rough estimate of how much oxygen can be consumed by reactions in a given solution. It's usually represented as the mass of oxygen utilized divided by the volume of the solution.

2. The COD value is an important criterion for determining water quality.

3. The above $\mathrm{O}_{2}$ can be obtained from 50 percent acidified potassium dichromate.

4. The higher the COD value, the more polluted the environment.

COD or BOD Value Determination:

• COD or BOD is measured in parts per million (ppm).

• It's the number of parts per million of oxygen required to make one million parts per million of water. or it's the number of milligrams of oxygen needed per liter of water.   

$\mathrm{COD} \text { or } \mathrm{BOD} \text { in } \mathrm{ppm}=\dfrac{\text { weight of } \mathrm{O}_{2}}{\text { weight of water }} \times 10^{6}$

h. TLV (Threshold Limit Value):

1. The threshold limit value is the lowest level of harmful compounds or pollutants present in the atmosphere that can harm a person when exposed to them for 8 hours per day in the workplace (TLV).

2. TLV stands for the maximum allowed amount of pollutants in industry and mining regions.

5. Environment Segments: 

There are four segments to the environment.

a) Atmosphere  b) Hydrosphere  c) Lithosphere  d) Biosphere

A) Atmosphere:

1. The atmosphere is the air layer that surrounds the world.

2. The atmosphere acts as a shield for the earth. It absorbs a portion of the sun's electromagnetic radiation and transmits near-ultraviolet, visible, and near-infrared radiation.

B) Hydrosphere: 

1. The hydrosphere is the fraction of the earth's water that is present.

2. Water covers four-fifths of the earth's surface.

3. In the hydrosphere, 97% of the water is in the form of seawater, 3% is ice in the polar ice caps, and traces of water are left for drinking and cultivation.

4. Many marine animals and plants survive in seawater, although it is not suitable for drinking.

C) Lithosphere: 

1. The rest of the earth's space, except for the hydrosphere, is made up of land. It's known as the Lithosphere.

2. Plants, animals, and humans live in the lithosphere, and minerals are found in the earth's surface inner layers.

D) Biosphere:

1. The biosphere is made up of all living species, including plants, animals, and humans.

2. The biosphere and other aspects of the environment are linked. The term "ecosystem" refers to the interaction that exists between all biological systems and their surroundings.

3. The biosphere and other aspects of the ecosystem are linked.

The Main Causes of Pollution Are: 

i) Population Growth, ii) Industrialization, iii) Urbanization, and iv) Deforestation.

There Are Four Parts to the Atmosphere:

i) Troposphere (0-11 kilometres); ii) Stratosphere (11-50 kilometres); iii) Mesosphere (50-85 kilometres); iv) Thermosphere (85-500km)

I) Troposphere (0-11km): 

1. The troposphere extends up to 11 kilometers above the earth's surface.

2. It is the most important part of the atmosphere since it includes air.

3. As altitude rises, the density of the air and the temperature drop.

II) Stratosphere: 

The stratosphere is the uppermost layer of the atmosphere (11-50km)

1. This section can be found between 11 and 50 kilometers above the earth's surface. It has an ozone layer in it.

2. The ozone layer absorbs ultraviolet (UV) energy from the sun, preventing it from reaching the planet. As a result, it serves as a protective layer.

III) Mesosphere: 

1. It exists between 50 and 85 kilometers above the earth's surface.

2. Sound waves are unable to propagate in this area.

IV) Thermosphere (Ionosphere): 

1. It exists between 85 and 500 kilometers above the earth's surface.

2. As we climb higher in this location, the temperature climbs to a maximum of 1473 K.

3. After absorption of solar energy, atmospheric oxygen undergoes ionization.

6) Air Pollution: 

1. Nitrogen, oxygen, and water vapor are the three main components of air.

2. Argon and carbon dioxide are small components in the air.

3. Tracer gases in the air include neon, helium, methane, krypton, nitrous oxide, hydrogen, xenon, sulfur dioxide, ozone, and ammonia, among others.

4. As we rise above the earth, the density and pressure of the air diminish.

5. Carbon oxides, such as carbon monoxide and carbon dioxide, are significant air pollutants. Other pollutants are Nitrogen oxides, Sulphur Oxides, Ozone, Chlorofluorocarbons (CFCs), Hydrocarbons (methane, butane, etc. Metals (heavy metals, lead, etc. ), Smog, Organic pollutants.

A. Carbon Monoxide (Co) : 

1. Smoke is produced as a result of incomplete combustion of gasoline and diesel in automobiles at high pressures and temperatures. Carbon monoxide is the major component of this smoke.    

$2 \mathrm{C}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CO}$

2. Methane is formed when organic stuff in fuel dissociates. This methane is also converted to carbon monoxide by oxidation.   

$2 \mathrm{CH}_{4}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{CO}+4\mathrm{H}_{2} \mathrm{O}$

3. In urban areas, carbon monoxide levels can rise to 50-100 ppm during peak hours, but the recommended limit of CO in the air is 9 ppm. CO reacts with blood hemoglobin to form carbonyl washarms hemoglobin, which is unable to transport oxygen.    

$\mathrm{Hb}+\mathrm{CO} \rightarrow \mathrm{Hb}-\mathrm{CO}$

The toxic effect is mostly owing to its significant proclivity for forming dative bonds with hemoglobin iron.

B. Nitrogen Oxides: 

1. The nitrogen oxides  \[\text{N}{{\text{O}}_{2}}\] and \[{{N}_{2}}O\] are the most common nitrogen oxides that pollute the air.

2. Nitrogen oxides are released during the burning of fossil fuels and vehicle fuels.

3. The maximum level of nitrogen oxides allowed is 10ppm. Plants are unable to undertake photosynthesis at concentrations higher than 10 ppm.

4. Nitric oxide reacts with ozone, causing the $\mathrm{O}_{3}$ to decompose into $\mathrm{O}_{2}$.    

$\begin{array}{l} \mathrm{NO}+\mathrm{O}_{3} \rightarrow \mathrm{NO}_{2}+\mathrm{O}_{2} \\ \mathrm{NO}_{2}+\mathrm{O}_{3} \rightarrow \mathrm{NO}+2 \mathrm{O}_{2} \end{array}$

C. Sulfur Oxides: 

1. Sulphur, sulfide ores, ores, and fuels containing sulfur discharge $\mathrm{SO}_{2}$ into the environment when they are burned.   

$\mathrm{S}+\mathrm{O}_{2} \rightarrow \mathrm{SO}_{2}$

2. $\mathrm{SO}_{2}$ damages the mucous membranes of the nose and respiratory tract, causing respiratory illnesses in humans.

3. $\mathrm{SO}_{2}$ changes the color of plants' leaves from green to yellow. Plants are unable to photosynthesize as a result of this.

D. Freons Of Chlorofluorocarbons (Cfcs):

1. Chlorofluorocarbons (CFCs) are chlorine, fluorine, and carbon-based man made chemicals that are sometimes referred to as "freon."

2. Trichlorofluoromethane is the most significant chlorofluorocarbon $\mathrm{CFCl}_{3}$

3. Chlorofluorocarbons (CFCs) are commonly utilized as refrigerant propellants, solvents, and foaming agents.

4. CFCs absorb UV radiation in the stratosphere and break down into radicals.     

\[\begin{array}{*{35}{l}} \text{CFC}{{\text{l}}_{3}}\to \text{CFC}{{\text{l}}_{2}}+\text{C}{{\text{l}}^{\text{o}}}  \\ \text{C}{{\text{l}}^{\text{o}}}+{{\text{O}}_{3}}\to\text{Cl}{{\text{O}}^{\text{o}}}+{{\text{O}}_{2}}  \\ \end{array}\]

E. Hydrocarbons: 

1. Methane is a hydrocarbon that is found in vast quantities all over the world.

2. Car exhaust contains a mixture of hydrocarbons such as methane, ethane, acetylene, propane, butane, and others.

3. Diesel engines produce benzopyrene, which causes cancer in humans.

4. Another hazardous chemical that harms plants is peroxyacetyl nitrate (PAN).

F. Metals: 

1. Lead particles can be found in exhaust gases from autos.

2. Carbon particles in the form of "aerosol" are present in industrial gases.

3. Metal factories emit metal particles into the atmosphere.

4. If the gasoline contains tetraethyl lead, methylene chloride, or ethylene bromide, lead particles are released into the air when the fuel is burned.

G. Photochemical Smog: 

1. Smog is the term for smoke and fog.

2. Los Angeles was the first place where photochemical smog was discovered.

3. Summer smog contains oxidizing chemicals and is referred to as oxidizing smog.

4. Reducing smog is created in the winter and contains reducing agents such as SO₂ and carbon.

H. Carbon Pollutants: 

1. Organic air contaminants include benzopyrene, pesticides, and biocides.

2. Harmful pesticides and biocides are released into the air by companies during the manufacturing process, polluting the environment and posing small to serious health risks.

I. Dust: 

1. In the form of dust, 22 metals are present in the air.

2. Metals such as zinc, copper, magnesium, and manganese are less abundant in the atmosphere, although calcium, silicon, aluminum, and iron are abundant.

3. Dust pollution is caused by excessive traffic and many industries.

7) Effects of Air Pollution: 

As a result of air pollution, the following hazards may occur: a) acid rain; b) ozone layer depletion; c) greenhouse effect or global warming.

a) Acid Rain: 

Nitric acid and sulfuric acid are produced when nitrogen and sulfur oxides combine, resulting in acid rain.    

$\begin{array}{l} \mathrm{NO}+\mathrm{O}_{3} \rightarrow \mathrm{NO}_{2}+\mathrm{O}_{2} \\ \mathrm{NO}_{2}+\mathrm{O}_{2} \rightarrow \mathrm{NO}_{3}+\mathrm{O}_{2} \\ \mathrm{NO}_{2}+\mathrm{NO}_{3} \rightarrow \mathrm{N}_{2} \mathrm{O}_{5} \\ \mathrm{~N}_{2} \mathrm{O}_{5}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{HNO}_{3} \\ \mathrm{SO}_{2}+\mathrm{O}_{2} \rightarrow \mathrm{SO}_{3} \\ \mathrm{SO}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}_{2} \mathrm{SO}_{4} \end{array}$

1. Acid rain refers to rainwater that contains nitric and sulphuric acids.

2. Acid rain is more prevalent in urban areas.

3. The pH of acid rain was roughly equal to 5 in 1918, but it was reduced to 4.2 in 1962.

4. The life of buildings will be significantly shortened as a result of acid rain.

5. The Taj Mahal's splendor is harmed by acid rain's effect on marble stones.

b) Depletion in the Ozone Layer: 

CFCs have caused holes in the O3 layer near the north and south poles of the earth.

1. A depletion in the ozone layer increases the amount of ultraviolet light falling on the earth by 3%.

2. UV rays have an impact on the photosynthetic process in plants.

C) Global Warming or The Greenhouse Effect: 

1. Infrared radiation reaching the ground is absorbed by carbon dioxide and water vapor, which is partly reflected in the earth's surface. The earth's surface heats up as a result of this. The greenhouse effect is the phenomenon of the earth's surface heating up.

2. The amount of $\mathrm{CO}_{2}$The atmosphere is increasing as a result of deforestation.

3. Ozone is a protective layer in the stratosphere, but it is damaging in the troposphere.

4. To combat global warming, more sinks must be created by planting trees and forests.

5. The amount of carbon dioxide in the atmosphere is 0.03 percent.

6. $\mathrm{CO}_{2}$is one of the gases that cause the greenhouse effect (50 percent ) $\mathrm{CH}_{4}$(carbon monoxide) (19 percent ). Other gases are chlorofluorocarbons (4 percent ), Oxygen (8 percent ), Nitrogen Oxide (4%), and Water Vapour (2%).

Industrial and agricultural waste are examples of organic pollutants.

Plastics, fibers, detergents, paints, peroxides, pesticides, weedicides, dyes, plasma chemicals, and other organic contaminants are examples. Sugar, paper, leather, and pulp industries produce industrial trash.

Food Chain: The carriers of contaminants from one place to another are referred to as the food chain. Plants, fish, birds, animals, and humans are all included.

Bioamplification: Bio-amplification refers to the increase in pollutant concentrations as we progress from lower to higher animals.

Eutrophication: Pollutants like $\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{~S}, \mathrm{H}_{2}, \mathrm{O}_{2}$ nitrates, phosphates, sulfate, boron, chlorine, copper, iron, etc. Will act as nutrients for the subsequent drying up that occurs is called eutrophic or over nutritious.

D. Fluorides: 

1. The concentration of fluorides up to 3 ppm in drinking water is harmless.

2. The lower and upper limits of fluoride concentration should be 1 ppm and 3 ppm, respectively.

3. Zirconium Alizarin-S dye can be used to determine fluorine levels.

4. With Zirconium-Alizarin-S, fluorine produces the colorless compound $\mathrm{ZrF}_{6}^{2-}$.

5. The drinking water in the districts of Nalgonda, Prakasam, and Guntur in our state includes an excessive amount of fluorine.

E. Drinking Water Defluoridation Techniques: 

1. Defluoridation refers to the process of eliminating fluoride ions from water.

2. Water is mixed with bleaching powder, lime, and alum and kept. The water's fluoride ions precipitate as complex calcium aluminum fluoride. This is filtered to obtain pure water. NEERI (National Environmental Engineering Research Institute) pioneered this technology.

Our Responsibility to the Environment: 

1. Many waste compounds, such as plastics, can be degraded using microorganisms and enzymes.

2. Pollutants are by-products of any reaction. As a result, procedures should be devised that produce no byproducts, resulting in an environmentally friendly reaction.

3. Non-conventional fuels and non-conventional energy systems must be employed instead of conventional fuels and energy systems.

4. Clean and environmentally friendly technology should be developed and implemented.

5. Population increase must be managed.

Activated carbon method: Activated carbon filters are utilized, and fluoride ions are absorbed by the carbon.

After some period of use, the filters get deactivated; to revive them, 4 percent $\mathrm{NaOH}$ and 1 percent $\mathrm{H}_{3} \mathrm{PO}_{4}$ are employed. Water that has been polluted has a lower $\mathrm{DO}$ value,  a higher BOD value, and a higher COD value.

i) A change in color and a rise in salinity are signs of polluted water.

ii) foul odor

iii) excessive weed growth

iv) A decrease in fish growth.

Contaminated water causes diseases like cholera, typhoid, jaundice, and diarrhea.

The Main Causes of Water Contamination Are: 

1. The Industrial Revolution

2. The Green Revolution

3. The Blue Revolution

4. Population growth.