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Excessive phytoplankton (organic pollutants such as leaves, grass trash etc.) growth which is present in water is biodegradable. Bacteria decomposes this organic matter in water. During this process when large number of bacteria decomposes the organic matter, they consume the dissolved oxygen in water. When the level of dissolved oxygen falls below 6 ppm then the fishes cannot survive and they die.

Excess of SO₄^2- in drinking water (500 ppm) may cause a laxative effect.

Those chemicals which check the growth of fungi are called fungicides.

Primary pollutants are those which after their formation remain as such, e.g., NO. Secondary pollutants are those which are formed as a result of reaction between primary pollutants, e.g., PAN (peroxyacylnirates).

(a) The presence of particulate matter in polluted air catalyses the oxidation of SO₂ to SO₃. The reaction is also promoted by ozone and hydrogen peroxide.

2SO₂ + O₂ \(\overset{Dust\,or\,soot\,particles}{\rightarrow}\) 2SO₃

SO_{2 +} O₃ \(\overset{hv}{\rightarrow}\) SO₃ + O₂

SO₂ + H₂O₂ → H₂O + SO₃

(b) The formation of ozone in the stratosphere takes place in two steps. In the first step, ultraviolet radiation coming from the sun has sufficient energy to split dioxygen into two oxygen atoms. In the second step, the oxygen atoms react with more of dioxygen to form ozone.

O₂ \(\overset{hv}{\rightarrow}\) O + O, O + O₂ → O₃

(c) Carboxyhaemoglobin (COHb).

Troposphere (0-11 km), Stratosphere (11 – 50), Mesosphere (50 – 85 km), Thermosphere (85 – 500 km).

When we go from one region of the atmosphere to the next adjoining region, the trend of temperature changes from increase to decrease or vice-versa. This is called inversion temperature.

(i) The catalytic converters are used in the automobile exhaust which in the first stage converts the oxides of nitrogen to free N₂ or to small amount of NH₃.

(ii) The fuel gases coming from power plants or industrial units and containing NO₂ and SO₂ are freed from these gases by scrubbing them with sulphuric acid.

It is highly poisonous to living beings because of its ability to block the delivery of oxygen to the organs and tissues. It binds to haemoglobin complex to form carboxyl haemoglobin (COHb) which is about 300 times more stable than oxy‐hemoglobin complex. In the blood when the concentration of carbon haemoglobin reaches about 3‐4 percent, the oxygen carrying capacity blood is greatly reduced. This oxygen deficiency, results in to headache, weak eyesight, nervousness and cardiovascular disorder CO₂ does not combine with haemoglobin and hence is less harmful as pollutant but it is the main contributor forwards green house effect & global warming.

Pathogens are disease causing microorganisms include bacteria, Virus etc. They enter into water from animal excreta and domestic sewage.

(i) Sodium chlorate (NaClO₃), (ii) Sodium arsenite (Na₃AsO₃).

NaClO₃ (sodium chlorate) and Na₃AsO₃ (Sodium Arsenite). 

1.Development of polystyrene foam sheet packaging material this Technology allows eliminations CFCs which contribute to ozone depletion, global warming and ground level smog.

2. Catalytic hydrogenation of diethanolamine in which environmental friendly herbicide is produced in less dangerous ways.

NaClO₃ (sodium chlorate) and Na₃AsO₃ (Sodium Arsenite)

(1) The ozone layer protects the earth from the harmful UV radiation 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 skin cancer and sun burns. 

(2) They cause death of many phytoplankton’s which lead to a decrease of fish productivity. 

(3) Increase in UV radiation, decreases the moisture content of the soil and damages both plants and fibres.

1. Recycling:‐materials are recycled which saves the cast of raw material and waste disposal.

2. Sewage treatment

3. Burning and Incineration

4. Digesting

5. Dumping

Ozone hole implies distribution of the ozone layer by the Harmful UV radiations the depletion will virtually result in creating some sort of holes in the blanket of ozone which surround us. As a result, the harmful radiations cause skin cancer, loss of sight and also affect our immune system

Ozone hole: There is depletion of ozone over Antarctica region commonly known as a ozone hole. Its consequences are that UV light can reach the earth which can lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplankton, damage to fish productivity etc. It has also been observered that plant protein get easily affected by UV radiation which leads to the harmful mutation of cells.

1. Recycling:‐materials are recycled which saves the cast of raw material and waste disposal. 

2. Sewage treatment

3. Burning and Incineration 

4. Digesting 

5. Dumping

Ozone hole implies depletion of the ozone layer by the Harmful UV radiations .This depletion will virtually result in creating some sort of holes in the blanket of ozone which surround us. As a result, the harmful radiations cause skin cancer, loss of sight and also affect our immune system

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 BOD value of less than 5 ppm, where as highly polluted water has a BOD of 17 ppm or more.

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 BOD value of less than 5ppm, where as highly polluted water has a BOD of 17ppm or more

1. H₂O + CO₂ ‐‐‐‐‐‐‐ > H₂CO₃

2. H₂CO₃ ‐‐‐‐‐‐ > H+ + HCO₃^‐

3. 2SO₂ + O₂ + 2H₂O ‐‐‐‐‐‐ > 2H₂SO₄

Chlorofluorocarbons are stable compounds. They move to stratosphere by random diffusion. These undergo decomposition in the presence of sunlight to release Cl atoms. 

These Cl atoms cause catalytic chemical reactions and cause significant depletion of ozone layer as shown below:

Cl₂CF₂ → Cl  + C ClF₂

Cl + O₃ → ClO ∙ + O₂

ClO + O → Cl∙ + O₂

Since the free radicals use ozone and convert it to oxygen, they cause thinning of ozone layer in stratosphere.

1. It is harmful for crops 

2. It damages buildings made up of marble.

(i) harmful to animals.

(ii) Harmful to plants.

(iii) Harmful to material life.

1. 2SO₂ + O₂ ‐‐‐‐‐‐ > 2SO₃

2. SO₂ + O₃ ‐‐‐‐‐‐‐ > SO₃ + O₂

3. SO₂ + H₂O₂ ‐‐‐‐‐‐ > 2H₂SO₄

Sources: Burning of fossil fuels containing sulphur

When the PH of the rain water below 5.6 due to the presence of oxides of sulphur & nitrogen and carbon dioxide in the atmosphere is called acid rain. Harmful effects of acid rain 

1. It is toxic to vegetation and aquatic life 

2. It damages building and states and dissolves heavy metals from soils, rocks and sediments. Taj Mahal has been damaged by acid rain. 

3. The heavy metal ions such as copper, lead and aluminium, leached from the soil, enter well water and produced variety of toxic effects. 

4. Acid rain also corrodes water pipes resulting in the leaching as heavy metals such as iron, lead and copper into drinking water.

(a) Refrigerants

Particulate air pollutant is Coal.

(c) Peroxy acetyl Nitrate

(d) Dissolved oxygen concentration below 5 ppm is ideal for the growth of fish.

The air around the statues and monuments in India contains fairly high levels of the oxides of sulphur and nitrogen. This is due to a large number of industries and power plants in the nearby areas. The problem has been further aggravated due to use of poor quality of coal, kerosene and fire wood as fuel for domestic purposes. The states acid rain affects for marble of these statues and monuments. 

CaCO₃+H₂SO₄ ‐> CaSO₄+H₂O+CO₂ 

As a result, this away and marble is getting discoloured and lusterless.

Chemistry and chemical process involving the minimum use and generation of harmful substances is called green chemistry

Ex:‐ Earlier tetrachloroethene themes was used as solvents for dry cleaning. This compound is carcinogenic; therefore it has been replaced by liquefied CO₂ along with a suitable detergent, which is less harmful.

(a) BOD: Biochemical oxygen demand is defined as the amount of oxygen required microorganisms to oxidise the organic pollutants presents in water. Water having BOD less than 5ppm is clean water and greater than 17ppm is polluted water 

(b) Photo chemical smog: It consists of oxides of nitrogen which absorb light and form free radicals. It is extremely harmful and is oxidizing in nature. 

(c) Ozone hole: ozone layer is depleted near Antarctica and it is called ozone hole.

The laxative effect is observed only when the concentration of sulphates in water is greater than 500 ppm. Sulphate is harmless at moderate concentration but concentration above 500 ppm produces laxative effects and hypertension.

Freons are Chiorofluoroalkanes.

Ozone layer is depicted by the reactive Chlorine atom.

(a) Both A and R are correct and R is the correct explanation of A.

Those pollutants which are directly emitted from the sources and pollute the air are called primary pollutants of the air.

Pollution of sea water due to discharge of wastes into it is called marine pollution.

Ultra violet rays will reach the earth after passing through the hole and cause skin cancer.

Chlorofluorocarbon causes depletion of ozone layer.

(a) Both A and R are correct and R is the correct explanation of A.

The main reason of ozone depletion is the release of chlorofluoro compounds (CFC’s) in the atmosphere also known as Freon.

Reducing is the nature of classical smog.