The chloro fluoro derivatives of methane and ethane are referred by trade name Freons. These Chloro Fluoro Carbon compounds are stable, non-toxic, noncorrosive and noninflammable, easily liquefiable and are used in refrigerators, air- conditioners and ln the production of plastic foams. CFC's are the exhaust of supersonic air craft's and jumbo jets in the upper atmosphere. They slowly pass from troposphere to stratosphere. ,They stay for very longer period of 50 - 100 years. In the presence of uv radiation, CFC's break up into chlorine free radical
CF₂Cl₂ \(\xrightarrow{hv}\) CF₂ CI +Cl.
CFCl₃ \(\xrightarrow{hv}\)CFCI₂+ Cl
Cl^o+O₃ ⟶ C10+O₂
Clo^o+O ⟶ CI+O₂
Chlorine radical is regenerated in the. course of reaction. Due to this continuous attack of Cl⁰ thinning of ozone layer takes place which leads to formation of ozone hole. It is estimated that for every reactive chlorine atom generated in the stratosphere 1,00,000 molecules of ozone are depleted.

(i) (a) Carbon Monoxide:
Carbon monoxide is a poisonous gas produced as a result of incomplete combustion of coal are firewood. It is released into the air mainly by automobile exhaust. It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest.
(b) Carbon dioxide:
Carbon dioxide is released into the atmosphere mainly by the process of respiration, burning of fossil fuels, forest fire, decomposition of limestone in cement industry etc.Green plants can convert CO₂ gas in the atmosphere into carbohydrate and oxygen through a process called photosynthesis. The increased CO₂ level in the atmosphere is responsible for global warming. It causes headache and nausea.
ii) a) Carbon Monoxide :
It binds with haemoglobin and form carbory haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest.
b) Carbon dioxide :
It causes headache and nausea.

Pesticides are the chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings. These are further classified as
a. Insecticides:
Insecticides like DDT ,BHC ,aldrin etc. can stay in soil for long period of time and are absorbed by soil . Th.y contaminate root crops like carrot, raddish, etc.
b. Fungicide :
Organo mercury compeunds are used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.
c. Herbicides :
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers. Example sodium chlorate (NaClO₃) and sodium arsenite (Na₃ As O₃). Most of the herbicides are toxic to mammals.

Standard characteristics of drinking water.

(i) Thus Greenhouse effect may be defined as the heating up of the earth surface due to trapping of infrared radiations reflected by earth's surface by CO₂ layer in the atmosphere.
(ii) The heating up of earth through the greenhouse effect is called global warming.
(iii) Without the heating caused by the greenhouse effect, Earth's average surface temperature would be only about -18 ^oC (0 ^oF). Although the greenhouse effect is a naturally occurring phenomenon, it is intensified by the continuous ernission of greenhouse gases into the atmosphere.
(iv) During the past 100 years, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled. If these trends continue, the average global temperature will increase which can lead to melting of polar ice caps and flooding of low lying areas. This will increase incidence of infectious diseases like dengue, malaria, etc.

There may be exercise concentration ( > 500 ppm) of sulphates in the ground water. So he could have felt laxative effect.

Without the heating caused by the greenhouse effect, earth's average surface temperature would be only about -18 ^oC (0 ^oF). Although the greenhouse effect is a naturally occurring phenomenon, it is intensified by the continuous emission of greenhouse gases into the atmosphere.
During the past 100 years, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled.If these trends continue, the average global temperature will increase which can lead to melting of polar ice caps and flooding of low areas. This will increase incidence of infectious diseases like dengu., malaria, etc.

a) The growth of algae in extreme abundance covers the water surface and reduces the oxygen concentration in water. Thus, bloom-infested water inhibits the growth of other living organisms in the water body. This process in which the nutrient rich water bodies support a dense plant population, kills animal life by depriving it of orygen and results in loss of biodiversity is known as eutrophication.
b) Chemicals from industries
c) Toxic pesticides
d) Detergents and oil floats
e) Acids from mine drianage and salts from various sources.

Particulate pollutants are small solid particles and liquid droplets suspended in air. Many of particulate pollutants are hazardous.
Examples : dust, pollen, smoke, soot and liquid droplets (aerosols) etc,.
They are blown into the atmosphere by volcanic eruption, blowing of dust, incomplete combustion of fossil fuels induces soot. Combustion of high ash fossil fuels creates fly ash and finishing of metals throws metallic particles into the atmosphere.
The non- viable particulates are small solid particles and liquid droplets suspended in air. They help in the transportation of viable particles. There are four types of non-viable particulates in the atmosphere. They are classified according to their nature and size as follows.
(i) Smoke : Smoke particulate consists of solid particles (or) mixture of solid and liquid particles formed by combustion of organic matter. 
For example, cigarette smoke, oil smoke, smokes from burning of fossil fuel, garbage and dry leaves.
(ii) Dust: Dust composed of fine solid particles produced during crushing and grinding of solid materials.
For example, sand from sand blasting, saw dust from wood works, cement dust from cement factories and fly ash from power generating units.
(iii) Mists : They are formed by particles of spray liquids and condensation of vapours in air.
For example, sulphuric acid mist, herbicides and insecticides sprays can form mists.
(iv) Fumes : Fumes are obtained by condensation of vapours released during sublimation, distillation, boiling and calcination and by several other chemical reactions.
For example : organic solvents, metals and metallic oxides form fume particles.

(i) Green chemistry is a chemical philosophy encouraging the design of products and Processes that reduce or eliminate the use and generation of hazardous substances.
(ii) For this, scientist are trying to develop methods to produce eco-friendly compounds. This can be best understood by considering the following example in which styrene is produced both by traditional and greener routes. To avoid carcinogenic benzene, greener route is to start with cheaper and environmentally safer xylenes.
(iii) Green chemistry means science of environmentally favourable chemical synthesis.

Ozone is formed by a series of reactions that occur from the sun shines

i. Bio-degradable pollutants :
The pollutants which can be easily decomposed by the natural biological processes are called bio-degradable pollutants.
Examples: plant wastes, animal wastes, etc.
ii. Non bio-degradable pollutants :
The pollutants which cannot be decomposed by the natural biological processes are called Non bio-degradable pollutants.
Examples : metal wastes (mainly Hg and Pb), D.D.T, plastics, nuclear wastes, etc., These pollutants are harmful to living organisms even in low concentration. As they are not degraded naturally,it is difficult to eliminate them from our environment.

At high altitudes to the atmosphere consists of a layer of ozone (O₃) which acts as an umbrella or shield for harmful UV radiations. It protects us from harmful effect such as skin cancer. UV radiation can convert molecular oxygen into ozone as shown in the following reaction.

Ozone gas is thermodynamically unstable and readily decomposes to molecular oxygen.

1. Waste management : Environmental pollution can be controlled by proper disposal of wastes. 
2. Recycling : a large amount of disposed waste material can be reused by recycling the waste, thus it reduces the land fill and converts waste into useful forms.
3. Substitution of less toxic solvents for highly toxic ones used in certain industrial processes. 
4. Use of fuels with lower sulphur content (e.g., washed coal)
5. Growing more trees
6. Control measures in vehicle emissions are adequate.
7. Green chemistry philosophy can be followed.
8. Eco-friendly compounds should be developed.
g. Greener routes should be followed in our day to day life.
10. For dry cleaning liquified CO₂ or H₂O₂ may be used.
11. Paper may be bleached by H₂O₂.
12. Methanol maybe used instead of petrol.
13. Neem based pesticides may be used.
14. Awareness among students and public may be created by using slogans like "Save water; Water will save You".

It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest.

(i) BOD and COD

(ii) Viable and non-viable particulate pollutants

Rain water normally has a pH of 5.6 due to dissolution of atmospheric CO₂ into it. Oxides of sulphur and nitrogen in the atmosphere may be absorbed by droplets of frater that make up clouds and get chemically converted into sulphuric acid and nitric acid respectively as a results of pH of rain water drops below the level 5.6, hence it is called acid rain. Acid rain is a by-product of a variety of sulphur and nitrogen oxides in the atmosphere. Burning of fossil fuels (coal and oil) in power stations, furnaces and petrol, diesel in motor engines produce sulphur dioxide and nitrogen oxides The main contributors of acid rain are SO₂ and NO₂.They are converted into sulphuric acid and nitric acid respectively by the reaction with oxygen and water.
2SO₂ + O₂ + 2H₂O ⟶ 2H₂SO₄
4NO₂ + O₂ + 2H₂O ⟶ 4HNO₃
Harmful effects of acid rain
Some harmful effects are discussed below :
(i) Acid rain causes extensive damage to buildings and structural materials of marbles. This attack on marble is termed as Stone leprosy.
CaCO₃ + H₂SO₄ ⟶ CaSO₄ + H₂O +CO₂ ↑
(ii) Acid rain affects plants and animal life in aquatic ecosystem.
(iii) It is harmful for agriculture, trees and plants as it dissolves and removes the nutrients needed for their growth.
(iv) It corrodes water pipes resulting in the leaching of heavy metals such as iron, lead and copper into the drinking water which have toxic effects.
(v) It causes respiratory ailment in humans and animals.