TS Inter 1st Year Chemistry Study Material Chapter 12 Environmental Chemistry

Telangana TSBIE TS Inter 1st Year Chemistry Study Material 12th Lesson Environmental Chemistry Textbook Questions and Answers.

TS Inter 1st Year Chemistry Study Material 12th Lesson Environmental Chemistry

Very Short Answer Type Questions

Question 1.
Define the terms atmosphere, biosphere.
Answer:
Atmosphere:
The blanket of gases that surrounds the earth is called Atmosphere. It contains large proportions of N₂ and O₂ and in small proportions CO₂, water vapour etc. It absorbs the harmful radiation coming from the Sun and plays an important role in maintaining the heat balance on earth.

Biosphere:
All living organisms, trees, plants, animals and human beings constitute Bio-sphere. This biosphere is interrelated to other segments of environment. Biosphere is dependent on atmosphere and hydrosphere.

Question 2.
Explain the terms Lithosphere, Hydro-sphere.
Answer:
Lithosphere :
One-fifth of the total earth surface is in the form of land. Inner layers of earth contain minerals. Deeper inner layers of earth contain natural gas and oil. All these things including hills and mountains come under this segment.

Hydrosphere:
All the natural water resources together constitute the Hydrosphere. It includes oceans, seas, rivers, lakes, streams, reservoirs, polar ice caps and ground water etc.

Question 3.
Define the term Soil Pollution.
Answer:
Lithosphere is the outer mantle of the solid earth consisting of minerals and the soil. The study of the pollution in this segment is called soil pollution.

Question 4.
What is Chemical Oxygen Demand (COD)? [AP, TS ’16, 15; IPE 14]
Answer:
The amount of oxygen required to oxidise organic substances present in polluted water is called a chemical oxygen demand. It is a parameter for measuring the water pollution. It is determined by oxidising the organic matter with acidified (50% H-jSO^ potassium dichromate solution.

Question 5.
What is Biochemical Oxygen Demand (BOD)? [AP ’16, ’15; IPE ’14 Mar. ’19, ’18 (TS)]
Answer:
The amount of oxygen used by the microorganisms present in water during five days at 20°C is called Biochemical oxygen demand (BOD). The BOD of pure water is about 1 ppm. If it is greater than 17 ppm it is highly polluted water.

Question 6.
What are Troposphere and Stratosphere?
Answer:
Troposphere :
Troposphere is the area of atmosphere from 0-11 km. It is the nearest region to the earth surface. It contains 70% of the atmospheric mass. It mainly contains N₂, O₂.

Stratosphere :
Stratosphere is the area of atmosphere between 10 and 50 km above the troposphere. It contains ozone layer. This ozone layer absorbs ultraviolet radiations from the sun and protect the life on earth.

Question 7.
Name the major particulate pollutants present in Troposphere.
Answer:
Particulate pollutants present in troposphere are dust, mist, fumes, smoke, smog etc.

Question 8.
List out four gaseous pollutants present in the polluted air.
Answer:

1. Oxides of Sulphur SO₂ and SO₃
2. Oxides of Nitrogen NO₂
3. Oxides of Carbon CO and CO₂
4. Hydrocarbons.

Question 9.
Greenhouse effect is caused by and [Mar. 18 (TS); (IPE 14)]
Answer:
Greenhouse effect is caused by carbondi- oxide, methane, ozone, chlorofluorocarbon compounds and water vapour gases.

Question 10.
Which oxides cause acid rain? And what is its pH value?
Answer:
SO₂ and NO₂ cause acid rain.
2SO₂ + 2H₂O + O₂ → 2H₂SO₄
4NO₂ + 2H₂O + O₂ → 4HNO₃
The pH of acid rain is about 5.6

Question 11.
Name two adverse effects caused by acid rains. [AP ’16, ’15; TS 15]
Answer:

1. Acid rain is harmful to agriculture, since it removes nutrients required for their growth.
2. Aquatic animals and plants die in where the acid rain falls.
3. Acid rain damages the buildings.
4. Metal pipes which carry water corrodes in acid rain.

Question 12.
What are smoke and mist?
Answer:
Smoke consists of solid or mixture of solid and liquid particles formed during combustion of organic matter. Eg. Cigarette smoke.

Mist is formed by the particles of spray liquids and by condensation of vapours in air. Eg. Sulphuric acid, herbicides, insecticides, etc. which miss their targets and go into air forming mist.

Question 13.
What is classical smog? And what is its chemical character (Oxidising, reducing)?
Answer:
Smog is formed from smoke and fog. Classical smog occurs in cool humid climate. It is a mixture of smoke, fog and sulphur dioxide. Chemically it is a reducing mixture in nature.

Question 14.
Name the common components of photochemical smog. [AP Mar. ’19]
Answer:
Photochemical smog occurs in warm, dry and sunny climate. The main components of photochemical smog are ozone, nitric oxide, acrolein formaldehyde and peroxy acetyl nitrate. It is oxidising in nature.

Question 15.
What is PAN? What effect is caused by it?
Answer:
PAN is peroxy acetyl nitrate. It is powerful irritant and causes corrosion of metals, stones, building materials, rubber and painted surfaces.

Question 16.
How is ozone formed in the Stratosphere?
Oxygen in the stratosphere converts into ozone by absorbing energy from the UV radiations of sunlight.

Question 17.
Give the chemical equations involved in the ozone depletion by CF₂Cl₂.
Answer:

Question 18.
What is Ozone hole? Where was it first observed?
Answer:
The holes formed in the ozone layer due to its depletion by polluted gases are called ozone holes. For the first time the formation of ozone hole was reported in 1980 at Antarctica of South Pole.

Question 19.
What is the value of dissolved oxygen in pure cooled, water?
Answer:
The value of dissolved oxygen in pure cooled, water is 4 – 6 mg L^-1

Question 20.
Give the possible BOD values of clean water and the polluted water.
Answer:
For pure water BOD is 1 ppm. If the BOD value of water is greater than 17 ppm, it is said to be polluted water. Municipal sewage has BOD values from 100 – 4000 ppm.

Question 21.
Name three industrial chemicals that pollute water.
Answer:
1. Pathogens:
These are bacteria and other organisms that cause diseases.

2. Organic wastes:
Such as leaves, grass, trash, excessive phytoplanktons etc.

3. Chemical pollutants :
These include water soluble inorganic chemicals and organic chemicals.

Question 22.
What agrochemicals are responsible for water pollution?
Answer:
Agrochemicals such as fertilisers containing phosphates, insecticides, pesticides, weedicides, fungicides are responsible for water pollution.

Short Answer Questions

Question 1.
What are different segments of the earth’s environment?
Answer:
Environment is divided into four segments. They are

1. Atmosphere
2. Hydrosphere
3. Lithosphere and
4. Biosphere.

1) Atmosphere :
The blanket of gases that surrounds the earth is called Atmosphere. It contains large proportions of N₂ and O₂ and in small proportions CO₂, water vapour etc. It absorbs the harmful radiations coming from the Sun and plays an important role in maintaining the heat balance on earth.

2) Hydrosphere:
All the natural water resources together constitute the Hydrosphere. It includes oceans, seas, rivers, lakes, streams, reservoirs, polar ice caps and ground water etc.

Four-fifths of the earth’s surface is occupied by water. Out of this 97 % is present in the form of sea water and the remaining 3 % is in the form of ice in polar ice caps and only very small percentage of water is available for drinking, agriculture and other human purposes.

3) Lithosphere :
One-fifth of the total earth surface is in the form of land. Inner layers of earth contain minerals. Deeper inner layers of earth contain natural gas and oil. All these things including hills and mountains come under this segment.

4) Biosphere:
All living organisms, trees, plants, animals, and human beings constitute Bio-sphere. This biosphere is interrelated to other segments of environment. Biosphere is dependent on atmosphere and hydro-sphere. Polluted atmosphere stops the plants’ growth and can create health problems among animals and human beings.

Question 2.
Define the terms Sink, COD, BOD, TLV and receptor. [AP Mar. ’17, ’13; TS ’16, ’15 Mar. ’18 (AP)]
Answer:
Sink :
The medium which reacts with pollutants is called sink.
Ex : Sea water is a big sink for CO₂.

COD :
The amount of oxygen required to oxidise organic substances present in polluted water is called Chemical Oxygen Demand. It is an important parameter for determining the quality of water.

BOD :
The amount of oxygen used by the suitable microorganisms present in water during five days at 20°C is called Biochemical Oxygen Demand (BOD).

TLV :
The minimum level of the toxic sub-stances or pollutants present in the atmosphere which affects a person adversely when he is exposed to this for 7 – 8 hrs. in a day is called Threshold Limit Value (TLV).

Receptor :
The medium which is affected by a pollutant is called receptor. [Mar. ’18 (AP)]
Ex : Eyes of drivers of two wheelers (or) four wheelers when they are stopped at signal centres.

Question 3.
Name the gaseous pollutants present in the air and explain their formation.
Answer:
Substances which mix with air and affect the human beings, animals, plants and global temperature are called air pollutants.

Examples:

1. Oxides of Carbon : CO and CO₂
2. Oxides of Nitrogen : N₂O and NO
3. Oxides of Sulphur : SO₂
4. Ozone
5. CFCs : Chlorofluorocarbons
6. Methane and Butane
7. Smog
8. Metals : Lead, Mercury.

Air pollution:
In cities 80% of air pollution is due to exhausts of automobiles. At peak times in cities the level of CO will be upto 50 -100 ppm. If it is inhaled, it causes adverse effects.

During the combustion of fossil fuels NO, N₂O, NO₂ etc. are also released. When the level of these oxides is greater than 10 ppm, the plants cannot perform photosynthesis.

SO₂ is released into the atmosphere during the burning of sulphur and roasting of sulphide ores. SO₂ causes respiratory diseases in human beings. It bleaches the green colour of the leaf apexes in plants to yellow colour and thus prevent photosynthesis process.

Chlorofluorocarbons when percolate into stratosphere cause depletion of ozone layer.

Harmful pesticides and biocides mix up with the air at their manufacturing units and pollute the air. They cause major health hazards.

Question 4.
What is greenhouse effect? and how is it caused? [AP Mar. ’17; May ’13; TS ’15]
Answer:
Greenhouse effect or Global warming :
Gases like CO₂, CFCs, O₃, NO and water vapour absorb I.R. radiations coming to the earth and reflect them back to the earth’s surface. Due to this, the surface of the earth gets heated. This is called greenhouse effect or global warming. The gases which are responsible for this effect are called greenhouse gases.

Effect of global warming :

1. For a 1°C rise in temperature, the ice caps of polar regions melt and level of the sea water increases. Thereby many coastal countries get submerged.
2. Due to global warming, the rate of evaporation of water from the seas, rivers, ponds will increase. This leads to unwarranted rains, cyclones and hurricanes.
3. Due to global warming, shortage of water supply for agriculture occurs.
   Global warming can be prevented by growing trees, forests, stopping production of CFCs etc.

Question 5.
Explain, with Chemical equations involved, the formation of acid rain. [TS Mar. ’19]
Answer:
Oxides of nitrogen and sulphur released from automobiles and industries enter into atmosphere and dissolves in water to form the acids HNO₃ and H₂SO₄. These acids dissolve in rain water and come down to earth as acid rain.
2SO₂ + 2H₂O + O₂ → 2H₂SO₄
4NO₂ + 2H₂O + O₂ → 4HNO₃

Question 6.
Explain in detail the adverse effects caused by the acid rain. [Mar. ’18 (AP)]
Answer:

1. Acid rain is harmful for agriculture. It washes away the nutrients required for the growth of plants. So crops cannot grow in the areas where the acid rain falls.
2. Aquatic animals and plants cannot live in acid water. So they die in the lakes, ponds, rivers where acid rain falls.
3. The metal pipes which carry water corrodes in the acid water where the acid rain falls.
4. Acid rain damages buildings and other structures made with stone or metal. Eg. Tajmahal in India has been affected by acid rain.

Question 7.
How is Photochemical Smog formed? What are its ill effects?
Answer:
When fossil fuels are burnt, a variety of pollutants are emitted into the earth’s troposphere. The hydrocarbons and nitric oxide after accumulated to sufficiently high levels, a chain reaction occurs from their interaction with sunlight. NO is converted into nitrogen dioxide (NO₂). This NO₂ again breaks up into NO and Oxygen by absorbing energy from sunlight.
NO₂ → NO + O

Oxygen atoms are very active and combine with the O₂ in air to produce ozone (O₃).
O + O₂ → O₃

The O₃ thus formed react with NO forming NO₂.
The O₃ and NO₂ are strong oxidising agents and can react with hydrocarbons present in air forming toxic chemicals such as formaldehyde, acrolein and peroxyacetyl nitrate (PAN). These all contribute to photochemical smog.

Question 8.
How is Ozone layer depleted in the atmosphere and what are the harmful effects caused by Ozone layer depletion?
Answer:
Ozone layer is depleted by the pollutant gases such as chlorofluorocarbons, NO₂ and HOCl.

The chlorofluorocarbons break down in the presence of sunlight and deplete the ozone layer as follows.

The chlorine radicals are continuously regenerated and cause the breakdown of ozone. One CFC molecule destroys one lakh O₃ molecules.

In winter season the \(\mathrm{Cl} \dot{\mathrm{O}}\) reacts with NO₂ forming chlorine nitrate. This hydrolyses giving hypochlorous acid and HCl. In summer season these break up providing \(\dot{\mathrm{C}l}\) radicals which can deplete the ozone layer.

Effects caused by ozone layer depletion:
Due to depletion of ozone layer the UV light coming from the sun directly reaches the earth and effects the life on the earth.

The UV radiations cause ageing of skin, cataract, sunburns, skin cancer, killing of phytoplanktons, damage the fish production etc.

It increases the evaporation of surface water and decrease the moisture content of the soil.

Question 9.
List out the industrial wastes that cause water pollution and what are the international standards fixed for drinking water?
Answer:
Process Wastes:
These are from inorganic process wastes and organic process wastes. Inorganic process wastes are present in the effluents from chemical industries, electro-plating industries, metallurgical and petroleum industries etc. These are mainly toxic but do not generally produce biological problems. Organic process wastes are from food processing industries, dairies, distillaries, paper, textile mills etc. It is very difficult to dispose organic process wastes.

Chemical Wastes:
Industries that manufacture acids, bases, detergents, explosives, dyes, insecticides, fungicides, fertilisers, silicones, plastics, resins, etc. which are generally used as raw materials for further manufacturing processes, contain chemical wastes. These wastes are produced during sedimentation, flocculation, washing, filtering, evaporation, distillation, electrolysis, absorption, crystallisation, burning, centrifusing etc. Chemical wastes are generally acidic, basic or toxic materials , coloured and inflammable. Chemical wastes require biological oxidation treatment methods like thickening filters, activated sludge or logooning.

The international standards fixed for drinking water.
Fluoride concentration – 1 ppm
Lead – 50 ppb
Sulphate – < 500 ppm
Nitrate – 50 ppm

Question 10.
Explain in detail the strategies adopted in Green Chemistry to avoid environmental pollution.
Answer:
The ways of using the knowledge and the principles of chemistry and other sciences to develop methods to reduce the pollution of the environment as far as possible are known as green chemistry.

The over exploitation of the soil using fertilisers and pesticides polluted the soil, water and air. But farming, irrigation etc. cannot be stopped. Then, methods to reduce the environmental pollution must be developed.

Generally in a reaction some by-products are formed. In many processes these by-products become the pollutants. Green chemistry works for not producing wasteful by-products in these processes.

Normal Process :

According to green chemistry the process shall be

As the reaction (2) gives no by-product it is called an environmental-friendly reaction. Even if a by-product is formed, it must be made a useful product instead of polluting the environment. Green chemistry suggests that instead of using conventional fuels and energy systems, non-conven- tional fuels and non-conventional systems must be put into practice. Because of this, pollution would be reduced.

Green chemistry is a cost effective approach that involves minimum chemical usage, minimum energy consumption and minimum waste (pollutant) generation.

Ex: In the dry cleaning of clothes, tetra-chloroethane was used earlier. This compound contaminates the ground water. Therefore, this compound is replaced by liquified CO₂ along with a suitable detergent. This would not pollute ground water much. Nowadays, H₂O₂ is used for bleaching clothes in laundries. This gives better results and decreases the consumption of water.

Long Answer Questions

Question 1.
What is environmental pollution? How many types of pollution are encountered?
Answer:
Due to increase in the population and industrialisation, the natural resources have diminished. To prepare many natural things artificially, many industries were started. For improving the yields many technologies were introduced. Along with this development, many waste products were released into environment. Thus environment got polluted. This is known as environmental pollution. Some reasons for environmental pollution are:

1. Increase in population and decrease in natural resources.
2. Industrialisation
3. Urbanisation
4. Deforestation

The different types of pollutions are

1. Air pollution
2. Water pollution
3. Soil pollution
4. Sound pollution
5. Thermal pollution
6. Radiological pollution

Question 2.
Explain the following in detail.
a) Global Warming;
b) Ozone depletion;
c) Acid Rain; d) Eutrophication
Answer:
a) Global Warming:
Greenhouse effect or Global warming :
Gases like CO₂, CFCs, O₃, NO and water vapour absorb I.R. radiations coming to the earth and reflect them back to the earth’s surface. Due to this, the surface of the earth gets heated. This is called greenhouse effect or global warming. The gases which are responsible for this effect are called greenhouse gases.

Effect of global warming :

1. For a 1°C rise in temperature, the ice caps of polar regions melt and level of the sea water increases. Thereby many coastal countries get submerged.
2. Due to global warming, the rate of evaporation of water from the seas, rivers, ponds will increase. This leads to unwarranted rains, cyclones and hurricanes.
3. Due to global warming, shortage of water supply for agriculture occurs.
   Global warming can be prevented by growing trees, forests, stopping production of CFCs etc.

b) Ozone Depletion:
Ozone layer is depleted by the pollutant gases such as chlorofluorocarbons, NO₂ and HOCl.

The chlorofluorocarbons break down in the presence of sunlight and deplete the ozone layer as follows.

The chlorine radicals are continuously regenerated and cause the breakdown of ozone. One CFC molecule destroys one lakh O₃ molecules.

In winter season the \(\mathrm{Cl} \dot{\mathrm{O}}\) reacts with NO₂ forming chlorine nitrate. This hydrolyses giving hypochlorous acid and HCl. In summer season these break up providing \(\dot{\mathrm{C}l}\) radicals which can deplete the ozone layer.

Effects caused by ozone layer depletion:
Due to depletion of ozone layer the UV light coming from the sun directly reaches the earth and effects the life on the earth.

The UV radiations cause ageing of skin, cataract, sunburns, skin cancer, killing of phytoplanktons, damage the fish production etc.

It increases the evaporation of surface water and decrease the moisture content of the soil.

c) Acid Rain :
Oxides of nitrogen and sulphur released from automobiles and industries enter into atmosphere and dissolves in water to form the acids HNO₃ and H₂SO₄. These acids dissolve in rain water and come down to earth as acid rain.
2SO₂ + 2H₂O + O₂ → 2H₂SO₄
4NO₂ + 2H₂O + O₂ → 4HNO₃

1. Acid rain is harmful for agriculture. It washes away the nutrients required for the growth of plants. So crops cannot grow in the areas where the acid rain falls.
2. Aquatic animals and plants cannot live in acid water. So they die in the lakes, ponds, rivers where acid rain falls.
3. The metal pipes which carry water corrodes in the acid water where the acid rain falls.
4. Acid rain damages buildings and other structures made with stone or metal. Eg. Tajmahal in India has been affected by acid rain.

d) Eutrophication :
When organic waste from agriculture and industry are released into lakes or ponds, the lakes are over bounded with over nutrients and large amount of phosphates. These can support the growth of algae. Such lakes are called Eutrophic lakes and the process is called eutrophication.

Question 3.
Green Chemistry is to avoid environmental pollution. Explain.
Answer:
The ways of using the knowledge and the principles of chemistry and other sciences to develop methods to reduce the pollution of the environment as far as possible are known as green chemistry.

The over exploitation of the soil using fertilisers and pesticides polluted the soil, water and air. But farming, irrigation etc. cannot be stopped. Then, methods to reduce the environmental pollution must be developed.

Generally in a reaction some by-products are formed. In many processes these by-products become the pollutants. Green chemistry works for not producing wasteful by-products in these processes.

Normal Process :

According to green chemistry the process shall be

As reaction (2) gives no by-product it is called an environmental-friendly reaction. Even if a by-product is formed, it must be made a useful product instead of polluting the environment. Green chemistry suggests that instead of using conventional fuels and energy systems, non-conven- tional fuels and non-conventional systems must be put into practice. Because of this, pollution would be reduced. Green chemistry is a cost-effective approach that involves minimum chemical usage, minimum energy consumption, and minimum waste (pollutant) generation.

Ex: In the dry cleaning of clothes, tetra-chloroethane was used earlier. This compound contaminates the groundwater. Therefore, this compound is replaced by liquified CO₂ along with a suitable detergent. This would not pollute groundwater much. Nowadays, H₂O₂ is used for bleaching clothes in laundries. This gives better results and decreases the consumption of water.