Environmental Chemistry

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Questions:

1 Marks

9 x 1 = 9

From where does ozone come in the photochemical smog?

Why 'photochemical smog' is called so?

Photochemical smog occurs in warm, dry and sunny climate. Among SO₂, NO₂, O₃ and hydrocarbons which one is not amongst the components of photochemical smog and why?

What is the composition of photochemical smog?

What is the nature of 'London smog' and why?

What are viable and non-viable particulates?

Name three natural sources of air pollution.

In what regions of the atmosphere,the temperature increases with altitude and in which regions it decreases?

Why does water covered with excessive algae growth become polluted?

Generic 3

5 x 3 = 15

10.

What are the reactions involved for ozone layer depletion in the stratosphere?

11.

VVhichgases are responsible for greenhouse effect? List some of them.

12.

Mr. Grover owner of a dry cleaning shop, was using terachloromethane eralier as a solvent for dry-cleaning. The compound containers the ground water and is also suspected carcinogenic. Mr. Raj owner of another dry cleaning shop is using CO₂ these days.
Hydrogen peroxide is being used for bleaching purpose.
(i) What is the advantages of using liquid Co₂ with suitable detergent for dry-cleaning?
(ii) What is the advantage of using H₂O₂ as bleaching agent?
(iii) What values are possessed by Mr. Raj?

13.

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.

14.

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.

Generic 5

3 x 5 = 15

15.

How can you apply green chemistry for the following?
(i) To control photochemical smog
(ii) To avoid use of halogenated solvents in dry
(iii) To reduce use of synthetic detergents
(iv) To reduce the consumption of petrol and diesel

16.

Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?

17.

Have you ever observed any water pollution in your area? What measures would you suggest to control it?

Generic 2

5 x 2 = 10

18.

While working in laboratory a student kept ferrous sulphate in a vessel made up of zinc. After few days he found cracks in the container.
(i) Why cracks were found in the container?
(ii) Write down the chemical reaction takes place.
(iii) What is the value associated with this?

19.

(i) State the Heisenberg's uncertainty principle.
(ii) Write down the significance of Heisenberg principle.
(iii) Do you think it has utility in your daily life? Justify your answer

20.

How is green chemistry a revolutionary step in protecting our environment and society?

21.

In your opinion what measures will you take to save your valuable monument from acid rain?

22.

How is ozone produced in the stratosphere?

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Answers Key:

1 Marks

9 x 1 = 9

()
In the presence of sunlight, NO₂ present in the air undergoes photolysis to form NO and atomic oxygen.
\(NO_{ 2 }\left( g \right) \underrightarrow { hv } NO\left( g \right) +\left( O \right) \left( g \right) \)
\(\left( O \right) \left( g \right) +O_{ 2 }\left( g \right) \longrightarrow O_{ 3 }\left( g \right) \)

()
It is because it is formed as a result of photochemical reaction (i.e. in the presence of sunlight) between oxides of nitrogen and hydrocarbons.

()
SO₂ is reducing in nature and not obtained in sunny and dry climate. So, it is not a component of photochemical smog. It is a component of classical smog.

()
It is a mixture of a number of irritation causing compounds like NO₂ , O₃ , peroxyacetyl nitrates (PAN), aldehydes, ketones, hydrocarbons and CO.

()
Reducing, because of the presence of SO₂ and carbon soot which are good reductant.

()
Viable particulates are small size living organisms such as bacteria, fungi, moulds, algae, etc. Non-viable particulates are formed by disintegration of large size materials ar condensation of small size particles or droplets, e.g. mist, smoke, fume, and dust.

()
Volcanic eruptions,forest fires and pollen grains of flowers.

()
Temperature increases with altitude in stratosphere and thermosphere while it decreases in troposphere and mesosphere.

()
Presence of excessive algal growth shows that water contains a lot of phosphate due to inflow of fertilisers, etc., from the surroundings. Hence, such a sample of water is polluted.

Generic 3

5 x 3 = 15

10.

The reaction can be shown as follows:
CF₂CI₂(g) + UV⟶ CI(g) + CF2Cl(g)
O(g) + O3(g) ⟶ CIO (g) + 02(g)
aO(g) + O(g) ⟶ CI + O2(g)

11.

CO₂ is mainly responsible for greenhouse effect. Other greenhouse gases are methane, nitrous oxide, water vapours, CFCs and Ozone.

12.

(i) It will result in less harm to ground water.
(ii) It gives better results and makes use of lesser amount of water
(iii) He is using better ecofriendly chemicals for dry cleaning and saving environment.

13.

The compost producing pit should be set up at a suitable place to protect ourselves from bad odour and flies biodegradable domestic wastes are put in the compost pit and it is covered with a little sand.
After some time, it is converted into compost by the action of heat and bacteria. Compost pit should be kept covered and the foul odour is minimise. Non-biodegradable domestic waste such as plastic, glass, metal scraps, polythene bags, etc., are sent for recycling. Recycling converts waste into wealth.

14.

Large quantities of phosphates and nitrates increase the growth of phytoplanktons. These phytoplankton use so much oxygen that it is not sufficiently available for other organism to use in respiration. Moreover, a large consume the oxygen dissolved in water, Microorganisms may become so abundant that they from a mat covering on the water surface and thereby preventing photosynthesis. In all these processes concentration of dissolved oxygen in water decreases. When the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets inhibited and they cannot survive.

Generic 5

3 x 5 = 15

15.

(i) Certain plants, e.g. Pinus, Juniparus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide (NO) and therefore, their plantation could help in reducing photochemical smog.
(ii) Liquefied CO₂ with a suitable detergent is used for dry cleaning and H₂O₂ is used for the better results and makes use of lesser amount of water.
(iii) Soaps are 100% biodegradable so they should be used in place of detergents. Now-a-days biodegradable detergents are available. Therefore, they should be used in place of non-biodegradable hard detergents.
(iv) CNG should be used as it causes much less pollution. Moreover, electrical vehicles should be used to reduce the consumption of petrol and diesel

16.

Yes, it can be controlled by the following methods.
(i) Insecticides, pesticides which are used for the protection of our crops cause soil pollution. Herbicides (weed killers) also cause soil pollution. Therefore, there is a need for their judicious use.
(ii) After the World War-II, DDT was put to use in agriculture to control the damages caused by insects, due to adverse effects, its use has been banned in India. Pesticides such as aldrin and dieldrin are organic toxins. These are water insoluble and physiological disorders in animals. Now a days organophosphates and carbamates are also used as pesticides. These are more biodegradable but these chemicals are severe nerve toxins and hence, more harmful to human
Therefore, chemicals like fertilisers, detergents pesticides polymers, should be used only when necessary
(iii) Biodegradable domestic waste should be deposited in land fills.
(iv ) Non- biodegradable waste should be recycled.
(v) use of polythene should be avoided.
(vi) Household waste, biological waste and chemical waste is often incinerated. Incineration greatly reduces the waste volume.

17.

Yes, polluted water is the water whose quality has been degraded by the addition of substance such as chemical effluents, metal residues, sewage, oil, fertilisers, detergents, etc.
It can be controlled by the following methods.
(i) Industrial waste discharge from paper, fertilisers, should not be allowed to get mixed in water bodies such as river, lakes, etc.
(ii) Non-biodegradable detergents should be used for cleaning of clothes
(iii) The ph of water should be checked.
(iv) Excessive use of fertilisers should be prevented.
(v) oils spills should be avoided as much as possible
(vi) Domestic waste water should be properly discharged and treated.
(vii) Avoid the use of DDT, malathion at home.
(viii) Waste water should be treated in sewage treatment plant.

Generic 2

5 x 2 = 10

18.

(i) Zinc is placed above iron in the reactivity series. It has therefore reduced Fe²⁺
ions to Fe.
(ii) Zn(s) + Fe²⁺⟶Fe(s) + Zn²⁺(aq)
(iii) One should be very careful in selecting container for storing certain chemicals.

19.

(i) According to Heisenberg, it is not possible to measure simultaneously the position and the momentum of a microscopic particle with absolute accuracy.
(ii) It has significance for microscopic particles. After his principle both wave and particle nature were considered and quantum mechanics was developed.
(iii) It has no impact on our daily life. It applies only to the moving microscopic particles which we cannot see with our eyes.

20.

Green chemistry is a way of utilizing the principles of chemistry to minimise the adverse impact on environment. It is a step to utilise our knowledge in reducing chemical hazards and put development activities in favour of saving environment.

21.

We know that monument like.Taj Mahal is being slowly disfigured and marble is getting discoloured. We can make people aware by passing this information. People living in city will be encouraged to use LPG in place of coal, kerosene or fire wood.

22.

Ozone in the stratosphere is a product of the action of UV radiations on dioxygen (O₂ ) molecules. The UV radiations split apart molecular oxygen into free oxygen atoms. These oxygen atoms combine with the molecular oxygen to form ozone.
\(O_{ 2 }\left( g \right) \underrightarrow { UV \ radiations } \left( O \right) \left( g \right) +\left( O \right) \left( g \right) \)
\(O_{ 2 }\left( g \right) +\left( O \right) \left( g \right) \begin{matrix} UV \\ \rightleftharpoons \\ Radiations \end{matrix}O_{ 3 }\left( g \right) \)