BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
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1. Define environmental chemistry.
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Solution:
The study of the origin, transport, reactions, effects and fates of chemical species that occur in
nature and those produced as a result of certain human activities is called environmental chemistry.
2. Explain tropospheric pollution in 100 words.
Solution:
Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air.
Particulate pollutants: These are dust, mist, fumes, smoke, smog etc.
Gaseous air pollutants: These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide,
hydrocarbons, ozone and other oxidants.
3. Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
Solution:
Carbon monoxide gas is more dangerous than carbon dioxide gas because Carbon monoxide reacts
with haemoglobin to form carboxy- haemoglobin which affects the capacity of haemoglobins to
oxygen transport.
4. List gases which are responsible for green house effect.
Solution:
The gases that are responsible for green house effect are carbon dioxide, methane, water vapours,
nitrous oxide, CFCs and ozone.
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5. Statues and monuments in India are affected by acid rain. How?
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Solution:
Statues and monuments made up of marble and limestone (CaCO3) are slowly corroded as the rain
water containing the acids fall on them. Actually, both sulphuric acid and nitric acid dissolve calcium
carbonate to form calcium sulphate and calcium nitrate respectively.
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CaCO3 + 2HNO3 → Ca(NO3)2 + CO2 + H2
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CaCO3 + H2SO4 → CaSO4 + CO2 + H2O
Since this salts are water soluble, they are slowly washed away resulting in slow corrosion of these
monuments and statues.
6. What is smog? How is classical smog different from photochemical smogs?
Solution:
Smog is a combination of 'smoke' and 'fog'. This is because it is formed for the first time due to the
condensation of some kind of fog on the carbon particles present in the smoke produced due to
combustion of domestic fuels and industrial fuels like coal and petroleum.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
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BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
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Difference between classical smog and photo chemical smog:
Classical Smog
Photochemical Smog
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1. This type of smog was first observed in London 1. This type of smog was observed in Los
in 1952.
Angeles in 1950.
2. It involves smoke and fog.
2. It does not involves any smoke or fog. The
word smog is misnomer here.
3. This type of smog is formed due to the
3. It is formed due to the photochemical
presence of SO2 and humidity in the air which
reactions taking place when air combines with
combines to from H2SO4 fog which deposits on the NO2 and hydrocarbons.
particles.
4. It is formed in the month of winter particularly 4. It is formed in the month of summer during
in the morning hour when the temperature is low. afternoon when there is bright sunlight so that
photochemical reactions can take place.
5. It causes bronchitis, irritations; problems in the 5. It causes irritation in the eyes.
lungs.
6. It is reducing in character.
6. It is oxidizing in character.
7. Write down the reactions involved during the formation of photochemical smog
Solution:
Photochemical smog is produced from the action of sunlight on the nitrogen oxides and hydrocarbons
present in the exhaust gases of the automobiles and factories. The NO is oxidized by the atmospheric
oxygen of NO2
High temperature
N2 + O2
2NO
2NO + O2
2NO2
NO2 (g) → NO (g) + O(g)
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NO2 then undergoes photochemical decomposition in the presence of sun light.
The free oxygen atom so formed reacts with atmospheric oxygen to form ozone.
Ozone then reacts rapidly with NO (g) to form NO2(g)
Fog + Smoke / dust + PAN → Photochemical smog.
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NO(g) + O2(g) → NO2(g) + O2(g)
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O2 (g) + O(g) → O3(g)
8. What are the harmful effects of photochemical smog and how can they be controlled?
Solution:
The harmful effects of photochemical smog are:
i) It decreases the visibility and thus affects the air and road traffic.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
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BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
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ii) It damages plants .
iii) Rubber on exposure to photochemical smog loses it elasticity and becomes inflexible and brittle.
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iv) Photochemical smog causes eye irritation.
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Control of Photochemical smog:
The best way to reduce the formation of photo chemical smog is to prevent the release of nitrogen
oxides and unburnt bydrocarbons into the atmosphere. Thus the simplest way to control photochemical smog is to
i) Minimise the use of personal vehicles
ii) Install efficient catalytic converters in automobiles. Photochemical smogs can also be suppressed
by using certain compounds that generate free radicals. These free radicals readily combine with the
free radical precursors of the photochemical smog.
9. What are the reactions involved for ozone layer depletion in the stratosphere?
Solution:
The reactions which deplete ozone layer in the stratosphere are
CF2Cl2(g) + hv → Cl-(g) + CF2Cl-(g)
Cl(g) + O3 (g) →€ClO-(g) + O2(g)
ClO.(g) + O(g) → .Cl(g) + O2(g)
The active .Cl(g) radicals are once again available for reacting with more ozone.
10. What do you mean by ozone hole? What are its consequences?
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Solution:
The ozone layer of lowered ozone concentration over Antartica is called ozone hole. This loss
occurred due to depletion of ozone in the ozone layer.
The consequences of ozone layer depletion are
i) It affects plants, chlorophyll, proteins and causes harmful mutation in them.
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ii) It will upset the heat balance of the earth.
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iii) It would cause ecological balances, which would adversely affect man and animals.
11. What are the major causes of water pollution? Explain.
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iv) Ultraviolet radiation coming from the sun can pass through stratosphere and reach on the earth,
causing cancer. Skin cancer chances are more.
Solution:
Water pollution can be caused in a number of ways:
Fertilizers
These are the chemical substances which are added to the soil to provide the essential minerals
containing N.P.S etc. the common fertilizers are calcium ammonium nitrate, urea, triple
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
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superphosphate, potassium sulphate, potassium nitrate etc. however, a certain part of these
fertilizers reacts with water chemically (known as leaching) and pollutes the underground water.
When this water is used for drinking purposes containing potassium nitrate in particular, it harms the
respiratory system.
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Pesticides
These include insecticides, fungicides, herbicides, rodenticides, etc. these are mostly chemically
chlorinated hydrocarbons, organophosphates, metallic salts etc. pesticides dissolve in water to small
extent and pollute it. Since all the pesticides are toxic in nature, they are injurious to both plants and
animals. The frequent use of pesticides without proper control can lead to deformities in foetus,
nervous system, stomach cancer, darkened skin and can also cause damage to eyes.
Organic Pollutants
It includes manures, wastes from food processing, rags, paper discards, decaying plants etc. and
other organic wastes. All of them cause pollution of water. They are decomposed by aerobic bacteria
into carbon dioxide, nitrates, sulphates, phosphates etc. but they take up dissolved oxygen from
water. As a result, the oxygen content in water decrease considerably. This causes the death of
aquatic animals particularly the fish.
Industrial wastes
The compounds of lead, mercury, cadmium, nickel, cobalt, zinc erc. Which are the products of
chemical reactions carried in the industrial units also pollute water to a large extent and are
responsible for many diseases.
12. Have you ever observed any water pollution in your area? What measures would you
suggest to control it?
Solution:
Yes, I have observed polluted water flowing in open sewage drains in my area.
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We can control if it by the following measures:
a. Sewage must be churned by machines so that the large pieces may break into smaller ones and
may get mixed thoroughly. The churned sewage is passed into a tank with a gentle slope. Heavier
particles settle and the water flowing down in relatively pure.
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b. Water must be sterilized with the help of chlorination. It kills microbes of sewage fungus as well as
some pathogens, spores or cytes. Chlorination is very essential particular in rainy seasons.
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13. What do you mean by Biochemical Oxygen Demand (BOD)?
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c. Treatment of water with alum, lime etc., also helps in its purification.
Solution:
BOD is Biochemical Oxygen Demand. It is a measure of dissolved oxygen that would be needed by
micro-organisms to oxidize some of the inorganic and organic compounds present in the polluted
water.
14. Do you observe any soil pollution in your neighbourhood? What efforts will you make
for controlling the soil pollution?
Solution:
We have observed soil pollution in nearby agricultural fields. This is due to the use of lot of fertilizers.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
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Fertilizers are chemical substances which helps the soil to become fertile. But excess of fertilizer pass
to the ground water from the soil and as run off to lakes rivers and seas, and are harmful to aquatic
animals.
The Control of soil pollution can be made by using manure and bio fertilizers instead of fertilizers:
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Use of manure
Manure is a semi- decayed organic matter which is added to the solid to maintain fertility. These are
mostly prepared from animal dung and other farm refuse. These are much better than the commonly
used fertilizers.
Use of biofertilizers
These organisms are inoculated in water to bring about nutrient enrichment of the solid, e.g.,
nitrogen fixing bacteria and blue- green algae.
15. What are pesticides and herbicides? Explain giving examples.
Solution:
Ans. Pesticides
Pesticides are basically synthetic toxic chemicals .They are used to kill or block the reproductive
processes of unwanted organisms. The repeated use of the some of similar pesticides gives rise to
pests that are resistant to that group of pesticides thus making the pesticides ineffective. Examples
are DDT, Aldrin, Dieldrin etc.
Herbicides
Herbicides are used to kill weeds. Sodium chlorate, NaClO3 and sodium arsenite Na3AsO3 were
commonly used as weed killers in the first half of the last century, but inorganic arsenic compounds,
inorganic arsenic compounds, in particular are toxic to mammals, organic herbicides are, therefore,
now used. They are much more toxic to certain types of plants than to others. Organic herbicides
such as triazines are presently widely used to kill weeds in corn fields.
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16. What do you mean by green chemistry? How will it help decrease environmental
pollution?
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Solution:
Green chemistry simply utilizes the information that is now available to the scientific community
about the toxicity and other hazards posed by certain chemicals in order to fully evaluate the
negative as well as positive impact of the chemistry being designed. Database of information on the
hazardous properties of chemicals have only recently become available. In the previous years the
absence of these data meant that chemists could not effectively evaluate the consequences of the
chemical substances that were being designed and synthesized. Since this is no longer the case, it is
the responsibility of the chemists and chemical community to use this information.
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It will help decrease environmental pollution because of the following processes:
Switch over to alternative fuels for an automobile reduces the pollution. Examples – uses of CNG in
Delhi has greatly reduced the pollution in the city.
Use of CO2 as blowing agent for the manufacture of polystyerene foam sheet packaging material has
eliminated the usage of CFCs which cause ozone depletion.
Designing of safer marine antifouling compound ‘Sea-nine’ that degrades far more rapidly than
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DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
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CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
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organotins which persist in the marine development and cause pollution problems.
Development of a new method to produce ibuprofen with 99% yield, avoiding the usage of large
quantity of solvents and wastes associated with the traditional methods.
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17. What would have happened if the green house gases were totally missing in the
earth’s atmosphere? Discuss.
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Solution:
The green house gas carbon dioxide takes part in the photosynthesis process carried out by green
plants to prepare food for plants and animals. In the absence of CO2, it will be not possible for green
plants to prepare food.
The green house gas, carbon dioxide produces green house effect, leading to the heating of earth
and its atmosphere, which is essential for our survival. In the absence of green house gases, heating
of earth and its atmosphere will not be possible.
18. A large number of fish are suddenly found floating dead on a lake. There is no
evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason
for the fish kill.
Solution:
Eutrophication causes a large number of fishes found floating dead of a lake. The presence of
phosphate anion encourages the formation of algae, which in turn reduces the concentration of
dissolved oxygen in water. This process of depletion of concentration of oxygen in water is called
eutrophication.
19. How can domestic waste be used as manure?
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Solution:
The domestic waste can be used as manure by digging a pit and domestic wastes are put in this pit.
A layer of soil is used to cover them. The decomposition is facilitated by pouring water. Manure in the
form of compost is obtained by this method.These manure are used in the fields. It is considered
better than the chemicals used as fertilizers because it does not causes pollution.
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20. For your agricultural field or garden you have developed a compost producing pit.
Discuss the process in the light of bad odour. Flies and recycling of wastes for a good
produce.
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Solution:
To develop compost first a pit is dug up and vegetable wastes and animal wastes like dung are put
into the pit. A layer of soil is used to cover them. Therefore, there will be no bad odour and flies. The
decomposition is facilitated by pouring water. Manure in the form of compost is obtained by this
method. These decomposed matters are used as manure. Since it is from organisms, it is simple
recycling of nutrients through soil. Crops, especially vegetables and fruits, grown by using manure
are considered safe as compared to crops grown by using chemical fertilizers.
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