1st PUC Chemistry Question Bank Chapter 14 Environmental Chemistry

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Karnataka 1st PUC Chemistry Question Bank Chapter 14 Environmental Chemistry

1st PUC Chemistry Environmental Chemistry One Mark Questions and Answers

Question 1.
Name a source of energy which does not create pollution.
Answer:
Sun is a source of energy which does not create pollution.

Question 2.
Which acid is not present acid rain?
Answer:
Acetic acid is not present in acid rain.

Question 3.
Name two insecticides.
Answer:
DDT and BHC are insecticides.

Question 4.
Define the term pollutant.
Answer:
Pollutant is any substance which cause adverse effect on environment.

Question 5.
Why is CO more toxic than CO₂?
Answer:
Carbon monoxide reacts with haemoglobin to form carboxy-haemoglobin which does not act as oxygen carrier. Therefore, it is more harmful than CO₂.

Question 6.
Name two gases which are responsible for green house effect.
Answer:
Carbon dioxide and methane.

Question 7.
Which part of atmosphere contains ozone layer ?
Answer:
Ozone layer is present in stratosphere.

Question 8.
What is full form of BOD and COD ?
Answer:
BOD stands for Biochemical oxygen demand whereas COD stands for chemical oxygen demand.

Question 9.
What is PAN ?
Answer:
PAN is Peroxycetyl nitrate

Question 10.
What is the percentage of CO₂ in the pure dry air?
Answer:
About 0.03%

Question 11.
What is the nature of London Smog ?
Answer:
It is reducing in nature.

Question 12.
Which has caused Bhopal gas tragedy ? Give its formula.
Answer:
Methyl isocyanate gas caused Bhopal gas tragedy. Its formula is CH₃ – N = C = O

Question 13.
What are pesticides ?
Answer:
Pesticides are those chemicals which are used to destroy pests, rats and parasite fungi.

Question 14.
What is meant by deoxygenation ?
Answer:
The process of removing dissolved oxygen from water by micro-organisms in order to oxidise organic matter of sewage is called deoxygenation.

Question 15.
Define incineration.
Answer:
It is the process of converting Organic materials to CO₂ and H₂O.

Question 16.
Define green chemistry.
Answer:
It involves processes and products that reduce or eliminate the use and generation of hazardous (harmful) substances.

Question 17.
What is meant y photo-chemical smog ?
Answer:
It is highly oxidising smog having high concentration of oxidizing agent like oxides of nitrogen which absorb sunlight and form free redicals.

Question 18.
What is marine pollution ?
Answer:
Pollution of sea water due to discharge of wastes into it is called marine pollution.

Question 19.
Which main compounds are causing damage to ozone layer ?
Answer:
NO and freons.

Question 20.
Which disease ’is caused due to hole in the ozone layer and why ?
Answer:
Ultra violet rays will reach the earth after passing through the hole and cause skin cancer.

Question 21.
Name two acids present in the acid rain.
Answer:
H₂SO₄ , HNO₃ and HCl.

Question 22.
What is effect of excess of \(\mathrm{SO}_{4}^{2-}\) ion in drinking water ?
Answer:
Excess of \(\mathrm{SO}_{4}^{2-}\) in drinking water (500 ppm) may cause a laxative effect.

Question 23.
Name the different regions of the atmosphere along with their attitudes and temperature ranges.
Answer:
Troposphere (0-11 km), Stratosphere (11 – 50), Mesosphere (50 – 85 km), Thermosphere (85 – 500 km).

Question 24.
What are fungicides ?
Answer:
Those chemicals which check the growth of fungi are called fungicides.

Question 25.
Give one example of organic herbicide.
Answer:
Triazine is an example of organic herbicide.

Question 26.
Give one main reason of ozone depletion.
Answer:
Chlorofluorocarbon causes depletion of ozone layer.

Question 27.
Define primary pollutant of the air.
Answer:
Those pollutants which are directly emitted from the sources and pollute the air are called primary pollutants of the air.

Question 28.
Write the name of gas produced in Mathura refineries which can damage the great historical monument “Taj Mahal”.
Answer:
Sulphur dioxide.

Question 29.
What type of radiations are abosorbed by CO₂ in the atmosphere ?
Answer:
Infrared radiations.

Question 30.
In which season and what time of the day, there is photochemical smog ?
Answer:
In summer, in the afternoon.

1st PUC Chemistry Environmental Chemistry Two Marks Questions and Answers

Question 1.
Define environmental chemistry.
Answer:
Environment chemistry deals with study of the origin, transport, reactions, effects and fates of chemical species in the environment.

Question 2.
Explain tropospheric pollution in 100 words.
Answer:
Trophospheric Pollution: It is due to presence of undesirable solid or gaseous particles in air.
1. Gaseous Air Pollutants: These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.
2. Particulate Pollutants: These are dust, mist, fumes, smoke and smog.

Question 3.
Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
Answer:
Carbon monoxide reacts with hemoglobin to form caboxy-hemoglogin which is 300 times more stable than oxy-hemoglobin complex. In blood, when concentration of carboxy-hemoglobin is about 3-4%, the oxygen carrying capacity of blood is greatly reduced. This oxygen deficiency, results into headache. Weak eye sight nervousness and cardiovascular disorder.

Question 4.
List gases which are responsible for green house effect.
Answer:
Carbon dioxide, methane, ozone, chlorofluorocarbons and water vapours in atmosphere are responsible for greenhouse effect.

Question 5.
Statues and monuments in India are affected by acid rain. How?
Answer:
Acid rain affects statues and monuments.
H₂O + CO₂ →H₂CO₃
\(\mathrm{H}_{2} \mathrm{CO}_{3} \rightleftharpoons 2 \mathrm{H}^{+}+\mathrm{CO}_{3}^{2-}\)
When pH of the rain drops below 5.6, it is called acid rain.
2SO₂ + O₂ + 2H₂O → 2H₂SO₄
3NO₂ +O₂ +2H₂O → 2HNO₃
CaCO₃ + H2SO₄ → CaSO₄ +H₂O+CO₂
(marble)
CaCO₃ + 2HNO₃ → Ca(NO₃)₂ + H₂O + CO₂

Question 6.
What is smog ? How is classical smog different from photochemical smog ?
Answer:
Smog, When smoke mixes with fog, it is called smog. It is of two types :
1. Classical smog: It occurs in cool humid climate and is the result of build-up of sulphur dioxides and particulate matter from fuel combustion. It is reducing in nature.

2. Photochemical smog : It occurs in warm, dry and sunny climate and results from the action of sunlight on the nitrogen oxides and hydrocarbons produced by automobiles and factories. It is oxidizing in nature.

Question 7.
Write down the reactions involved during the formation of photochemical smog.
Answer:
Mechanism of formation of Photochemical Smog:
\(\mathrm{NO}_{2}(\mathrm{g}) \stackrel{\mathrm{hv}}{\longrightarrow} \mathrm{NO}(\mathrm{g})+\mathrm{O}(\mathrm{g})\)
O(g) + O(g) → O₃(g)

Question 8.
What are the harmful effects of photochemical smog and how can they be controlled ?
Answer:
Effects :

• Smog causes respiratory problems like asthma attacks bronchitis, heart related disorder.
• It also causes irritation to eyes, throat and nose.
• It reduces visibility and affects road as well as traffic.
• It damages plants and other materials like electronic and electrical equipment.

Control :

• Efficient catalytic converters in the automobiles will reduce smog formation as it prevents the release of nitrogen oxides and hydrocarbons to the atmosphere.
• It can also be suppressed by certain compounds which acts as fuel radical traps. When these compounds are sprayed in the atmosphere, they generated free radicals which readily combine with free radicals responsible for formation of photochemical smog.

Question 9.
What do you mean by ozone hole ? What are its consequences ?
Answer:
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.

Question 10.
What are the major causes of water pollution ? Explain.
Answer:
Causes of water pollution
1. Pathogens : The disease causing agents are called pathogens like bacteria that enter water from domestic sewage and animal excreta.

2. Organic wastes : Leaves, grass, trash etc., pollute water. Excessive growth of photoplankton within water is also source of water pollution.

Question 11.
Have you ever observed any water pollution in your area ? What measures would you suggest to control it?
Answer:
Yes, there is water pollution. Sewage water should not be mixed with drinking water. Water purifier should be used before drinking water.

Question 12.
What do you mean by Biochemical Oxygen Demand (BOD)?
Answer:
It is defined as the amount of oxygen required by bacteria to break down organic materials present in water.

Question 13.
Do you observe any soil pollution in your neighbourhood ? What efforts will you make for controlling the soil pollution ?
Answer:
Yes, there is water pollution. We can prevents soil pollution by using less pesticides, insecticides, fungicides, weedicides DDT which has been banned should not be used. Organo-phosphates and carbamates should be used instead of Aldrin and Dieldrin. Sodium chlorate and sodium arsenite are also not environment friendly. Fields should be deweeded manually.

Question 14.
What are pesticides and herbicides ? Explain giving examples.
Answer:

• Pesticides: Those which are used to kill pests, insects which are harmful for the crops, e.g., Aldrin, Dieldrin B.H.C. etc.,
• Herbicides: Those chemicals which are used to destroy weeds i.e., unwanted plants are called herbicides, e.g., sodium chlorate, sodium arsenite etc.

Question 15.
What do you mean by green chemistry? How will it help in decreasing environmental pollution?
Answer:
Green Chemistry: It is the way of thinking and is about utilizing the existing knowledge and principles of chemistry and other services to reduce the adverse effect of pollutants.
1. Avoiding use of organic solvents such as benzene, toluene, CCl₄ etc., which are highly toxic, we can save our environment.

2. Use of CO₂ instead of CFC’s for thermocol can reduce pollution or depletion of ozone layer.

Question 16.
What would have happened if the greenhouse gases were totally missing in the earth’s atmosphere ? Discuss.
Answer:
If greenhouse gases are totally missing from earth’s atmosphere then temperature of earth will decrease. Plants cannot carry out photosynthesis if CO₂ is not present. Human beings cannot survive without plants.

Question 17.
Name the oxides of nitrogen. What are the sources ?
Answer:
Nitrogen monoxide (NO), Nitrogen dioxide (NO₂), Dinitrogen trioxide (N₂O₃),
Dinitrogen tetroxide (N₂O₄), Dinitrogen pentoxide (N₂O₅)
The source of oxides of nitrogen are combustion of fossil fuel, especially, petroleum.
They are also formed by reaction of N₂ and O₂ in presence of lightening.

Question 18.
Discuss the harmful effects of oxides of sulphur.
Answer:
Oxides of sulphur are SO₂ and SO₃. They cause acid rain which damages plants, animals and buildings. SO₂ irritates the respiratory system of animals and humans. They are harmful for lungs. They are harmful for plants. They increase rate of mortality.

Question 19.
What is the §ffect of dust particles present in atmosphere and why ?
Answer:
Dust particles suspended in the atmosphere effectively reduces the amount of light rays reaching the surface of earth and thus lower the temperature of the earth. They contribute to increased fog and rain in cities. They may reduce visibility and produce blurring effect on vision.

Question 20.
Discuss the pollution caused by thermal power plants.
Answer:
The gases like CO₂, CO, SO₂, SO₃ and oxides of nitrogen are formed due to combustion of fossil fuels in thermal power plants. Fly ash is also formed by combustion of high ash fossil fuel in thermal power plants.

Question 21.
How does detergent cause water pollution?
Answer:

• Detergent are non-biodegradable and they cause water pollution.
• They inhibit oxidation of organic substances present in waste water because they form a sort of envelope around them.
• They form stable foam in rivers which extend over several hundred meters of the river water.

Question 22.
How is greenhouse effect responsible for global warming ?
Answer:
Greenhouse effect is the phenomenon in which earth’s atmosphere traps the heat from the sun and prevents it from escaping into outer space. Carbon dioxide, methane, ozone, chlorofluorocarbons and water vapours absorb infrared radiations and increase the temperature of earth which is called global warming.

1st PUC Chemistry Environmental Chemistry Four Marks Questions and Answers

Question 1.
What is environment chemistry ? Discuss is social relevance.
Answer:
Environment chemistry deals with study of the origin, transport, reactions, effects and fates of chemical species in the environment.
Mankind is faced with several types of pollution such as air pollution, water pollution, soil pollution, thermal pollution, noise pollution, metals pollution etc.
It is most essential to control various types of pollution so as to save mankind and living organisms.

Question 2.
Define an environmental pollutant. What do you understand by an environmental pollution model?
Answer:
The substances which cause adverse effect on the environment are called environmental pollutants. In an environmental pollution process, a pollutant originates from a source and gets transported by air or water or is dumped on a land by man. Some of the pollutants may be absorbed (assimilated) or chemically changed by the environment; the rest build-up to concentrations which are harmful to environment.

Question 3.
State briefly the reactions causing ozone layer depletion in the stratosphere.
Answer:
The decomposition products of CFCs destroy ozone as it is shown in the following reaction:
CF₂Cl₂ (g) + hv → Ci(g) + \(\dot{\mathrm{C}}\)F₂Cl(g)
\(\dot{\mathrm{C}}\)l(g) + O₃(g) → Cl\(\dot{\mathrm{o}}\)(g) + O₂(g)
Cl\(\dot{\mathrm{o}}\)(g) + O(g) → Cl + O₂(g)

Question 4.
Write short note on Green Chemistry.
Answer:
Green Chemistry : It involves designing and development of green chemical products and processes which do not create pollution.

• Use of CNG has reduced air pollution in Delhi.
• Development of a new method to produce ibuprofen in 99% yield avoiding the usage of large quantity of solvents and wastes associated with the traditional methods.
• Using CO₂ as blowing agent for manufacture of polystyrene foam sheet packaging material has eliminated the use of CFCs which cause ozone depletion.
• Designing of a safer marine antifouling compound ‘Sea-nine’ that degrades far more rapidly than organizations which persists in the marine environment and cause pollution problems.

Question 5.
How is photochemical smog formed ? What are its effects ? How can it be controlled?
Answer:
Photo Chemical smog : Nitrogen monoxide is formed by reaction of N₂ and O₂ at high temperature in petrol and diesel engines of cars and trucks. NO is oxidized into the air to form NO₂ which absorbs energy from sunlight and breaks up into NO and free oxygen atom.
\(\mathrm{NO}_{2}(\mathrm{g}) \stackrel{\mathrm{hv}}{\longrightarrow} \mathrm{NO}(\mathrm{g})+\mathrm{O}(\mathrm{g})\)
Oxygen atoms are’very reactive and can combine with O₂ to form O₃
O(g) + O₂ (g) → O₃ (g).
Ozone reacts with NO to form NO₂ and O₂
NO + O₃ → NO₂ + O₂
The brownish haze of photochemical smog is largely due to brown colour of NO₂.
Effects : Pungent smelling, smog produced ozone is known to be toxic. It can cause coughing, wheezing, bronchitis and irritation to mucous system.

Control of photochemical smog :

• Installation of efficient catalytic converters in the automobiles is one of the ways of reducing smog formation.
• It can be suppressed by certain compounds, which acts as free radical traps. When these compounds are sprayed in the atmosphere they generate free radicals which readily combine with free radical precursors of photochemical smog.

Question 6.
What is the cause of acid rain ? How is it harmful to the environment ?
Answer:
When rain falls through polluted air, it comes across chemicals such as gaseous oxides of sulphur, oxides of nitrogen, mists, of hydrochloric acid and phospheric acid etc., pH lowers down from 5.6 to 3.5 sometimes it becomes as low as 2.

Question 7.
Distinguish between photochemical smog and classical smog.
Answer:

Photochemical smog	Classical smog
1. it is formed by oxides of nitrogen, hydrocarbons,etc.,	1. It is formed by oxides of sulphur carbon and particulate matter from combustion
2. It is oxidizing in nature	2. It is reducing in nature
3. Photochemical smog occurs in cities having large numbers of vehicles. It is not harmful	3. It occurs in both urban and rural areas. It is harmful

Question 8.
Describe the following in brief:
1. Ozone depletion over Antarctica (do not write reaction)
2. BOD and COD
3. Eutrophication
Answer:
1. Ozone depletion over Antarctica: In summer season, nitrogen dioxide and methane react with chlorine monoxide preventing ozone depletion whereas in winter, special type of clouds called polar stratosphereic coulds are formed over Antartica. These clouds provide surface on which chlorine nitrate molecules formed gets hydrolysed to form HOCl. It also reacts with HCls to give Cl₂. When sunlight returns to Antarctica again ozone depletion starts by free radicals.

2. BOD: It is amount of oxygen required by bacteria to decompose organize wastes present in water.
COD: It is the amount of oxygen (in ppm) required to oxidize the contaminants. COD is determined by using chemical oxidizing agent K₂Cr₂O₇.

3. Eutrophication: The process in which nutrient enriched water bodies support a dense plant polulation which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.

1st PUC Chemistry Environmental Chemistry Five Marks Questions and Answers

Question 1.
Explain International standards for drinking water.
Answer:
The quality of water is of vital concern for mankind because it is directly linked with human welfare. The drinking water should be fit for human consumption having the following essential parameters for water quality:

1. It should be colourless and odourless.
2. It should be pleasant in taste.
3. It should be clear and turbidity should be less 10 ppm.
4. Its pH should be between 5.5 to 9.5.
5. The total dissolved solids should not be more than 500 ppm.
6. It should be free from disease causing microorganisms.

Question 2.
Explain causes of soil pollution.
Answer:
The main sources of soil pollution are:

1. Improper disposal of human and animal excreta, solid and liquid wastes.
2. Domestic refuse and industrial wastes dumped on the land.
3. Wastes from mining of coal and other minerals dumped on the land.
4. Fertilisers and pesticides used in agriculture.
5. Radioactive refuge from laboratories, industries and hospitals.
6. Removal of the upper fertile layer of soil.