Environmental Chemistry - Class 11 Medical Chemistry - Extra Questions

The smoke and dust particles are not the cause of air pollution.

Particulate matter is the sum of all solid and liquid particles suspended in air, many of which are hazardous. This complex mixture contains for instance dust, pollen, soot, smoke, and liquid droplets.

These particles come in many different size ranges such as coarse, fine and ultrafine. They also vary in composition and origin.

They are either directly emitted into the air by sources such as combustion processes and windblown dust, or formed in the atmosphere by transformation of emitted gases such as sulphur dioxide.

Hence, The smoke and dust particles are causes of air pollution.


____________ the second layer of the atmosphere reaches $$48 $$ km above the earth's surface.

Troposphere lies between 5-20 km. Stratosphere is between 20-50 km. Mesosphere lies between 50-85 km.
So correct answer is stratosphere


What are the causes of water pollution? Discuss how can you contribute in reducing the water pollution.

Water pollution can be caused by the addition of
(i) undesirable substances like fertilizers and pesticides or any poisonous substances.
(ii) sewage directly entering a water body.
(iii) hot water from the power plant that increases the temperature and reduces the dissolved oxygen in water thus killing the aquatic organisms.
(iv) industrial effluents or radioactive substances in the water body.
We can take following measures to check water pollution
(i) The sewer lines should not be directly connected to the water body.
(ii) We should not throw our garbage or domestic wastes into the water body.
(iii) Prevent dumping of toxic compounds in the water bodies.
(iv) Washing of clothes should be avoided near water bodies as it adds a lot of detergents to it.
(v) Plant trees near the banks of the river to check soil erosion otherwise erosion leads to siltation of water body.


Discuss why pesticides are used in very accurate concentration and in very appropriate manner?

Pesticides are used in very accurate concentration and in a very appropriate manner because if used in excess 
(a) It harms the soil and causes loss of fertility.
(b) It checks the replenishment of organic matter.
(c) It kills the microorganism of soil.
(d) It causes air, water, and soil pollution.


In Antarctica ozone depletion is due to the formation of following compound.

Chlorine nitrate (ClONO$$_2$$)

The severe depletion of the Antarctica ozone layer known as the ozone hole and it occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctica stratosphere cause polar stratospheric clouds (PSCs) to form. These clouds contain Chlorine nitrate.



What is ozone depletion?

It is the reduction in the concentration of ozone in the ozone layer or ozonosphere.


Discuss why pesticides are used in very accurately in plants?

Pesticides should not be used indiscriminately. Only very accurate dose should be applied at appropriate time, slight excess of the pesticide is extremely harmful.
(i) Pesticides are harmful to soil biota. Therefore, they reduce soil fertility.
(ii)They pass into ground water and make it toxic.
(iii) They enter the crop plants and make them toxic.
(iv) Pesticides pass into surface water through run off from sprayed fields and harm the aquatic biota.


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 .

Proper care should be taken of the compost producing pit in order to protect ourselves from bad orders and flies.
To minimize bad odor, it should be kept covered. This will also prevent flies from entering it.
The recyclable waste should not be dumped in the compost producing pit. It should be sent to the industries through vendors for recycling.


What are the major causes of water pollution? Explain.


Several human activities leads to presence of several undesirable substances in water which causes water pollution.  Various sources of different water pollutants are shown below.

 Pollutant Source
 Micro-organisms Domestic sewage
 Organic wastes
 Domestic sewage, decaying animals and plants, animal excreta and waste, discharge from food processing industries.
 Plant nutrients
 Chemical fertilizers
 Toxic heavy metals
 Chemical factories and industries
 Sediments Strip mining and soil erosion
 Pesticides Chemical used for killing fungi, weed, insects
 Radioactive substances
 Mining of uranium-containing minerals
 Heat Water used for cooling in industries.


What do you mean by Biochemical Oxygen Demand (BOD)?

The amount of dissolved oxygen needed by aerobic biological organisms in a body of water to breakdown organic material present in a given water sample at certain temperature over a specific time period is called BOD.


What are pesticides and herbicides? Explain with examples.

A mixture of two or more substances used for killing pests are called pesticides. pests include insects, plant pathogens, weeds, mollusks, etc, that destroy the plant crop and spread diseases. Aldrin and dieldrin are the names of some common pesticides.
Herbicides are pesticides specially meant for killing weeds. Examples include sodium chlroride ($$NaClO_3$$), sodium arsenite ($$Na_3AsO_3$$) etc.


What do you mean by green chemistry? How will it help decrease environmental pollution?


Green chemistry is a production process that aims at using the existing knowledge and principles of chemistry for developing and implementing chemical products and processes to reduce the use and generation of substances hazardous to the environment.

The philosophy of encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. Green chemistry seeks to reduce and prevent pollution at its source and can, therefore, play a major role in decreasing the environmental pollution.


Explain 'tropospheric pollution' in 100 words or less.

The presence of unwanted substances in the lowest layer of the atmosphere results in tropospheric pollution. They are usually classified as gaseous and particulate pollutants. 

  • Major gaseous pollutants include oxides of sulphur, nitrogen, carbon and hydrocarbons.
  • Particulates of smoke dust mist and fume are harmful to human health and cause respiratory ailments.


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

Industrial wastes and agricultural pollutants such as pesticides, fertilizers etc are major sources of soil pollution.
The quality and fertility of soils should be maintained to ensure and sustain the growth of plants and food crops.
DDT is water insoluble. Hence, DDT (and other such insecticides) remain in soil for a long time and contaminate the root crops.
Pesticides such as Aldrin and Dieldrin are non biodegradable and highly toxic in nature. They can enter the higher trophic levels through food chains, causing metabolic and physiological disorders. The same is true for industrial wastes that comprises of several toxic metals such as Pb, As, Hg, Cd etc.
Control measures :
The addition of pollutants to the soil should be avoided. Also, proper treatment should be given to wastes. They should first be recycled and then dumped.


How water gets polluted? How the pollution can be minimised?

Chemical waste from factories is sometimes dumped into river and lake, or directly into the ground. Pesticides (a chemical that kills insects) applied to farmland either surface water and groundwater, often large quantities, which led to pollution.
To reduce water pollution, use natural cleaners like vinegar and baking soda in place of toxic chemicals like bleach and ammonia. Additionally, avoid using pesticides and herbicides in order to prevent groundwater contamination.


Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Eutrophication is when the environment becomes enriched with nutrients. It is a natural process in lakes, occurring as they age through geological time. It causes structural changes to the ecosystem such as increased production of algae and aquatic plants,  general deterioration water quality and other effects leading to the deficiency of oxygen in the water which affects the survival of aquatic organisms like fishes etc.


How is the ecosystem under threat due to waste accumulation?

Effect of accumulated waste on ecosystem:

  • Hazardous waste can cause depletion natural resources as they are corrosive and toxic in nature
  • Being poisonous they can cause serious illness to human and animal health.
  • Some wastes have ignitability and catch fire leading to fire accidents
  • They undergo violent chemical reactions and produce many toxic gases polluting environment.
  • The wastes also invite a huge number of pathogens causing many infectious diseases.
  • They cause degradation of land, pollution of water and also affect aquatic life.



Which aerosol depletes ozone layer?

Chlorofluorocarbons$$ (CFCs)$$ and other halogenated ozone depleting substances $$(ODS)$$ are mainly responsible for man-made chemical ozone depletion. When a $$CFC$$ molecule breaks down, it releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created.


Why do we care about atmospheric ozone?

Stratospheric ozone is considered good for humans and other life forms because it absorbs ultraviolet (UV)-B radiation from the Sun. If not absorbed, UV-B would reach Earth’s surface in amounts that are harmful to a variety of life forms. In humans, increased exposure to UV-B increases the risk of skin cancer, cataracts, and a suppressed immune system.



Write in details about the production of stratospheric ozone?

Ozone is naturally produced in the stratosphere by a two-step reactive process. In the first step, solar ultraviolet radiation (sunlight) breaks apart an oxygen molecule to form two separate oxygen atoms. In the second step, each atom then undergoes a binding collision with another oxygen molecule to form an ozone molecule. In the overall process, three oxygen molecules plus sunlight react to form two ozone molecules. Overall reaction :

O2 + ℎνuv → 2$$O^.$$

$$O^.$$ + O2 ↔ O3



Explain stratosphere.

The stratosphere is the second major atmospheric layer above the troposphere, extending in altitude from about 8 to 30 miles high. No weather occurs in the stratosphere. The statosphere contains over 15% of the total mass of the atmosphere, and is where the ozone layer is located.


Explain the stratospheric pollution.

Stratospheric pollution: It means depletion of the ozone layer (ozone hole) by certain compounds like oxides of nitrogen, chlorofluoro carbons (CFCs). 


Explain the stratospheric chemical reaction.

Stratospheric ozone is produced by a combination of an oxygen atom $$'O'$$ with an oxygen molecule $$'O_2'$$.
The steps are:
$$O_2+UV\longrightarrow O+O$$
$$2O+2O_2+third\quad molecule \longrightarrow 2O_3+third\quad molecule$$
Net reaction $$3O_2+UV\longrightarrow 2O_3$$


What do you understand by ozone layer? Write an essay to participate in the elocution competition on the importance of ozone layer.

The ozone layer is a layer of ozone high up in the Earth's atmosphere stratosphere. In the region between about 10 kilometres and about 50 kilometres above ground, the atmosphere contains more ozone (O3). The exact amount of ozone that can be found varies, the seasonsinfluence it; it is also different in different places on the Earth. [1] This layer can absorb between 93 and 99 per cent of the ultraviolet radiationfrom the sun.[2] This radiation is dangerous to many living organisms on Earth.

The Ozone layer is present in two layers of the atmosphere.
The sun radiates a huge variety of radiations such as ultraviolet radiations which are very harmful to the human body. It is the ozone layer which helps to absorb the ultraviolet radiation rays. It also helps to prevent them from reaching the surface of the earth. In this way, they help to save us from harmful rays. The ozone layer which is present naturally in the lower layers of the atmosphere helps in eradicating the pollutants from the surface of the earth.

If there were no ozone layer, the health of every single living being on planet Earth would be threatened. The depletion of the Ozone layer leads to an increased exposure to ultraviolet light, which can cause many health problems. When we are exposed to ultraviolet light, it enhances the risks of cataract development and skin cancer. It is very much possible to treat skin cancer in their early stages. It can, however, be deadly in the advanced stages. A growth in the eye is known as a cataract and they cloud the vision. It can also result in blindness. Enhanced exposure to UV also causes decreased growth of phytoplankton. Phytoplankton is the light-sensitive organism that forms the base of the ocean’s food web and at the same time, it is also responsible for removing much of the carbon dioxide from the atmosphere. Also, a thinning ozone layer would produce lower crop yields. There are many crops like rice which are sensitive to ultraviolet light. Increased UV exposure could make these crops less productive or even kill them. A major population of the earth is dependent on rice as a primary source of food.

The ozone layer is very important for life on earth. It protects us from harmful UV rays that can have serious effects on biodiversity, animals and people’s health, including skin cancer and eye cataract.

The experts have blamed the ozone-layer depletion on man-made chemicals containing chlorine and bromine that are emitted from a number of products and industrial processes.

• The Montreal Protocol in 1987 has been successful in curbing many of the substances that are most destructive to the ozone layer.
• Continued usage of methyl bromide and HCFCs, the banks of chemicals in existing equipment in buildings and the illegal trade in chemicals are areas that require more action. We will not be able to survive without the ozone layer as in the absence of the ozone layer one might suffer from various diseases like skin cancer, eye disorders etc. The harmful UV rays will also destroy crops and ocean life.




What emissions from human activities lead to ozone depletion? And what are the principle steps in stratospheric ozone depletion caused by human activities?

Ozone depletion is caused due to the CFCs and other such depleters.
$$O_3+\overset {\bullet}{Cl}\longrightarrow Cl\overset {\bullet}{O}+O_2$$
CFCs convert ozone to oxygen molecules. Principal steps in ozone depletion are emission of CFCs, then reaching the stratosphere and then depletion of layer.


Give uses of ethanol as fuel. How it conserves fossil fuel.

Uses of ethanol as fuel:
1) It is used as an alternative to Gasoline.
2) Anhydrous ethanol can be blended with gasoline in varying quantities to reduce the consumption of petroleum fuels.
3) It can also be used to power fuel cells and to produce biodiesel.
Thus, uses of gasoline as a fuel conserve the fossil fuel such as petroleum, gasoline, etc.


What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas?

$$\bf{Hint-}$$
Study about the waste materials and their effect on the river or seawater.

$$\bf{Concept-}$$
Sewage contains harmful microorganisms such as bacteria, viruses, and protozoa which can cause diseases such as gastroenteritis, amoebiasis etc .

$$\bf{Explanation-}$$
Sewage contains wastage from households, industrial, and agricultural activities. Sewage contains harmful chemicals and disease causing organisms. Hence, It is harmful to discharge untreated sewage into rivers or seas, as it can pollute whole water body. 


2011 is the international year of chemistry. "Chemistry is our life, our future", is the motto.
"Chemistry is not a problem but a solution" is the message of green chemistry. Explain the relevance of this message.

Green Chemistry: Manufacturing goods without causing environmental problems and ensuring the protection of living beings has become more relevant these days. A new branch of science has emerged for this. It is called green chemistry.
Green chemistry tries to create a new generation of eco-friendly products by converting harmful chemicals into harmless and useful materials during the production process. The message of green chemistry is that chemistry is not a problem but a solution.


What do you mean by the following:
i. Sewage
ii. Eutrophication
iii. Recycling

i. Sewage is the collective name of the wastewater and human waste from houses and other buildings.
ii. Eutrophication is a process by which a water body becomes enriched in dissolved nutrients, mainly phosphates, that stimulate the growth of aquatic plant life which usually resulting in the depletion of dissolved oxygen.
iii. Recycling is the practice of reusing items that would otherwise be discarded as waste.


Very Short Type Question
How is ozone important for us?

It protects us from the harmful effect of the sunrays.


What is green chemistry? Write one importance of green chemistry.

Green chemistry - It is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.

Importance of green chemistry:

  • Designing safer chemical production
  • Food and flavour production
  • Pharmaceutical industry
  • Paper and pulp industry


How pesticides, herbicides and fungicides are effecting the ecosystems?

Pesticides, herbicides and fungicides have various impacts on ecosystem such as:
  • The excessive use of pesticides, herbicides, and fungicides cause soil pollution and water pollution.
  • They make the soil infertile.
  • As they become a part of the soil, they are taken up by the plants. Due to this, the toxic substances get incorporated into the food chain.
  • The run-off from the fields leads to their entry in the water bodies which not only affects aquatic biota but also has serious health hazards on the humans. For example, excess nitrogen in the water causes the blue baby syndrome in children.
  • The chemicals and toxic substances once enter the food chain, get accumulated in the body of organisms and their concentration increases with each successive trophic level. This is called biomagnification. For example, DDT gets accumulated in the body of fishes as it enters water bodies due to runoff from the fields. 


What is an ozone layer in the starts the distribution of the ozone layer in the stratosphere?

The ozone layer is a region of Earths stratosphere that absorbs most of the suns ultraviolet radiation. It contains high concentrations of ozone in relation to other parts of the atmosphere, although still small in relation to other gases in stratosphere.


Name of the chemical responsible for destructive of the ozone layer. Start the main  chemical from these chemicals which is responsible for more then $$80\%$$ onzen depletion. Start the man -made applications which make of the chemical.

Ozone layer is depleted by man-made chlorofluro carbon, which are used as a coolant in the refrigerator and as aerosol propellants .they are long-lived molecule and they diffuse into stratosphere .they undergo photochemical dissociation to produce chlorine atoms; which deplete ozone at a rate than its formation.


What is meant by soil erosion?

Soil Erosion is the movement of topsoil from the upper part of the soil profile due to the action of wind or running water as a result of changes brought about by human activities like deforestation.


Explain any six principles of green chemistry. 

Six principles of Green Chemistry:-
(i) Waste Prevention- Prioritize the prevention of waste, rather than cleaning up & treating waste after it has been created. Plan ahead to minimize waste at every step.
(ii) Atom Economy- Reduce waste at the molecular level by maximizing the number of atoms from all reagents that are incorporated into the final product.
(iii) Design safer Chemicals- Minimize toxicity directly by molecular design.
(iv) Catalysis- Use catalyst instead of stoichiometric reagents in reactions in order to increase selectivity, minimize wastage.
(v) Reduce Derivatives- Minimize the use of temporary derivatives such as protecting groups to reduce reaction steps, resources required and waste created.
(vi) Real-Time pollution Prevention- Monitor chemical reactions in real-time as they occur to prevent the formation and release of any potentially hazardous and polluting substances.


Which liquid is found on the feather of birds and animal fur?

The birds align their feathers by combing their feathers during which they distribute the recreations or waxes from the preen gland located at the base of tail throughout the plumage. Animals also contain the same gland recreating oils that keep their body warm. 


Which type of fertilisers pollute water?

Water polluted by those fertilizers, which contain the soluble elements. Like nitrogenous fertilizer as nitrate form that is soluble in water. So it contaminates the groundwater and surface water also.


"Solving the problem of pollution is an effective way of environmental management" Justify the statement.

Pollution prevention is the practice of reducing or eliminating wastes or pollutants at the source. Pollution prevention, planning and implementation are therefore the most common basis for environmental management. Also, according to the intergovernmental panel on climate change, pollution and sustainable development are the two primary spots for the management of the environment. So, it can be said that solving the problem of pollution is an effective way of environmental management. 


Fill in the blanks : 
Use of excessive .............. by farmers causes water pollution.


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What is Green Chemistry?

Green Chemistry is the design of chemical products and the processes to reduce or eliminate the use and generation of hazardous substances.


a) Name the following method of solid waste management.
b) What type of waste is used in this method ?
c) What kind of useful substance can be obtained from such methods ?
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Write the future products of Green chemistry.

Future products of Green chemistry-
  • Green Dry-cleaning of clothes-
Tetrachloroethene $$\left( {Cl}_{2}C=C{Cl}_{2} \right)$$ was earlier used as solvent for dry cleaning. The process using this compound is now being replaced by a process, where liquefied carbon dioxide, with a suitable detergent, is used. Replacement of halogenated solvent by liquid $$C{O}_{2}$$ will result in less harm to groundwater.
  • Bleaching of paper-
Chlorine gas was used earlier for bleaching paper. These days, hydrogen peroxide $$\left( {H}_{2}{O}_{2} \right)$$ with a suitable catalyst, which promotes the bleaching action of hydrogen peroxide, is used.
  • Synthesis of chemicals-
Ethanal $$\left( C{H}_{3}CHO \right)$$ is now commercially prepared by one step oxidation of ethene in the presence of an ionic catalyst in an aqueous medium with a yield of $$90 \%$$.


What are the principal chemical species present in the stratosphere?


  • The increased temperature in this layer is due mainly to $$UV$$ absorption by various chemical species, including ozone and molecular oxygen present in the stratosphere.
So inorganic compounds such as ozone, nitrogen oxides, nitric acid, sulphuric acid, halogens and halogen oxides from $$CFC's$$ are the dominant chemicals in the stratosphere
  • so, ans. $$O_3, O_2, N_2$$, and some water vapours.



Can pollution of environment occur without human intervention? Explain.

Pollution of the environment cannot occur without human intervention.

Deforestation occurs when humans clear forests to use the land either for agriculture or for habitation leading to soil erosion and extinction of plant species. Land animals also decline in numbers and even face extinction due to human expansion that encroaches on their natural habitat and limits their ability to spread geographically.

One of the biggest environmental impacts of human activities is air quality. The transportation sector contributes heavily to air pollution because most forms of transportation, including cars, planes and ocean vessels, use fossil fuels. When burned, fossil fuels release carbon dioxide and other greenhouse gases into the environment.

In order to support the growing population, forests are being destroyed at an alarming rate. Humans also continue to put a great demand on the natural resources of our planet. Many non-renewable resources are being depleted due to the unrestrained use of fuel and energy. 

Many parts of the world also suffer from a shortage of food and water. The growth of the population puts larger demands on our already limited resources. The environment on earth is suffering from the growth of the global population. The depletion of resources and biodiversity, the production of waste, and the destroying of natural habitat are serious problems.


Describe stratosphere briefly.

The stratosphere extends from 11 km to 50 km. This region is rich in ozone which absorbs harmful UV radiations of the sun and converts them into heat. In this way UV radiations are prevented to reach the earth. Ozone is formed from oxygen by a photochemical reaction.

Besides ozone, the stratosphere also contains nitrogen, oxygen and a small amount of water vapour. This region is free from turbulent conditions or changing weather patterns.


Describe troposphere briefly.

$$Troposphere$$ is the lowest region of the atmosphere( closest to the earth). It extends to a height of about 11 Km. It contains mainly nitrogen and oxygen. The minimum temperature is at 11 km above the earth's surface. This point is called the tropopause.

Weather changes like rain, lightning, hurricane, etc occur in this region.

The pollution of troposphere occurs due to the presence of undesirable gases like $$CO_2,SO_2,SO_3,NO_2$$, etc. The particulate pollution include $$dust,mist,fumes,smoke\space aerosols$$.


Define pollution. Give its main causes.

Any undesirable change of the physical, chemical or biological characteristics in the air, water and land which is harmful to man directly or indirectly through his animals, plants, industrial units or raw materials is termed as $$Pollution$$.

Main causes of pollution are:
(i) $$Urbanisation$$
(ii) $$Industrialisation$$
(ii) $$Over$$ $$population$$
(iv) $$Deforestation$$


Name the regions of atmosphere where global warming and ozone depletion phenomenon occur.

Global warming occur in Troposphere and Ozone depletion occur in Stratosphere.


Give three suggestions for minimising pollution.

(i) $$Non$$ $$conventional$$ $$methods$$ of producing energy should be developed. The use of fossil fuels should be reduced.

(ii) Proper $$sewage$$ $$disposal$$ $$plants$$ and recovery of sewage water for various industrial and domestic purposes should be established. Domestic garbage should be profitably utilised.

(iii) $$Manures$$ and $$Biofertilizers$$ should be used in place of chemical fertilizers.


What is the wavelength range of the ultraviolet radiation which is removed in the stratosphere?

Ultraviolet radiations between $$190$$ to $$340\ nm$$ are removed in the stratosphere.
The ozone layer (which absorbs from about $$200\ nm$$ to $$310\ nm$$ with maximal absorption at about $$250\ nm$$) is very effective at screening out $$UV-B$$; for radiation with a wavelength of $$290\ nm$$, the intensity at the top of the atmosphere is $$350$$ million times stronger than at the Earth's surface.



Growth in human population has direct effect on pollution. Explain.

One of the largest environmental effects of human population growth is the problem of Global warming.

Economic development, urbanization, energy consumption, transportation/motorization due to rapid population growth are major driving forces of air pollution in large cities.

In order to support the growing population, forests are being destroyed at an alarming rate. Deforestation occurs when humans clear forests to use the land either for agriculture or for habitation. This leads to soil erosion and the extinction of plant species. Land animals also decline in numbers and even face extinction due to human expansion that encroaches on their natural habitat and limits their ability to spread geographically.

Humans also continue to put a great demand on the natural resources of our planet. Many non-renewable resources are being depleted due to the unrestrained use of fuel and energy. Many parts of the world also suffer from a shortage of food and water. 

The growth of the population puts larger demands on our already limited resources. The environment on earth is suffering from the growth of the global population. The depletion of resources and biodiversity, the production of waste, and the destroying of natural habitat are serious problems.


How can air pollution be controlled.

Air pollution can be controlled by the following measures:

i) Fuels such as CNG (compressed natural gas) and LNG (liquefied natural gas) which release minimum quantities of pollutants on combustion should be used in place of gasoline.

ii) Use of renewable energy sources like hydroelectric energy, solar energy, geothermal energy.

iii) Industrial emissions are major causes of air pollution, the pollutants can be controlled or treated at the source itself to reduce its effects.

iv) Tree plantation - Plants and trees reduce a large number of pollutants in the air. 


Define green chemistry.

Green chemistry is defined as the design, development and implementation of chemical products and processes to reduce or eliminate the use and generation of substances hazardous to human health and environment.


What do you mean by green chemistry? How it will help in decreasing environmental pollution?

Green chemistry is a production process that aims at using the existing knowledge and principles of chemistry for developing and implementing chemical products and processes to reduce the use and generation of substances hazardous to the environment.


The release of different harmful chemicals (particulates, gases, organic and inorganic wastes) causes environmental pollution. In green chemistry, the reactants to be used in chemical reactions are chosen in such a way that the yield of the end products is up to $$100\%$$. 

This prevents or limits chemical pollutants from being introduced into the environment. Through the efforts of green chemists, $$H_2O_2$$ has replaced tetrachlorethane and chlorine gas in drying and bleaching of paper.



What suggestions would you like to give to minimise the pollution?

Follow these Tips Every Day to Reduce Pollution:

  1. Conserve energy - at home, at work, everywhere.
  2. Look for the ENERGY STAR label when buying a home or office equipment.
  3. Carpool, use public transportation, bike, or walk whenever possible.
  4. Follow gasoline refueling instructions for efficient vapor recovery, being careful not to spill fuel and always tighten your gas cap securely.
  5. Consider purchasing portable gasoline containers labeled “spill-proof,” where available.
  6. Keep car, boat, and other engines properly tuned.
  7. Be sure your tires are properly inflated.
  8. Use environmentally safe paints and cleaning products whenever possible.
  9. Mulch or compost leaves and yard waste.
  10. Consider using gas logs instead of wood.



Name at least four soil pollutants. Explain one of them.

Soil pollution refers to anything that causes contamination of soil and degrades the soil quality. It occurs when the pollutants causing the pollution reduce the quality of the soil and convert the soil inhabitable for microorganisms and macro organisms living in the soil.

Some of the most hazardous soil pollutants are:

Industrial Waste

The discharge of industrial waste into soils can result in soil pollution. Some common soil pollutants that can be sourced to industrial waste are listed below.

  • Chlorinated industrial solvents
  • Dioxins produced from the manufacture of pesticides and the incineration of waste.
  • Plasticizers/dispersants
  • Polychlorinated biphenyls (PCBs)

The petroleum industry creates many petroleum hydrocarbon waste products. Some of these wastes, such as benzene and methylbenzene, are known to be carcinogenic in nature.

Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (often abbreviated to PAHs) are organic compounds that:

  • Contain only carbon and hydrogen atoms.
  • Contain more than one aromatic ring in their chemical structures.

Common examples of PAHs include naphthalene, anthracene, and phenalene. Exposure to polycyclic aromatic hydrocarbons has been linked to several forms of cancer. These organic compounds can also cause cardiovascular diseases in humans.

Soil pollution due to PAHs can be sourced to coke (coal) processing, vehicle emissions, cigarette smoke, and the extraction of shale oil.

Heavy Metals

The presence of heavy metals (such as lead and mercury, in abnormally high concentrations) in soils can cause it to become highly toxic to human beings. These metals can originate from several sources such as mining activities, agricultural activities, electronic waste (e-waste), and medical waste.

Pesticides

Pesticides are substances (or mixtures of substances) that are used to kill or inhibit the growth of pests. Common types of pesticides used in agriculture include:

  • Herbicides – used to kill/control weeds and other unwanted plants.
  • Insecticides – used to kill insects.
  • Fungicides – used to kill parasitic fungi or inhibit their growth.

However, the unintentional diffusion of pesticides into the environment (commonly known as ‘pesticide drift’) poses a variety of environmental concerns includes soil pollution.



Define green chemistry. What are its objectives?

Green chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, use, and ultimate disposal. Green chemistry is also known as sustainable chemistry.

Green chemistry:

Prevents pollution at the molecular level
Is a philosophy that applies to all areas of chemistry, not a single discipline of chemistry
Applies innovative scientific solutions to real-world environmental problems
Results in source reduction because it prevents the generation of pollution
Reduces the negative impacts of chemical products and processes on human health and the environment
Lessens and sometimes eliminates hazard from existing products and processes
Designs chemical products and processes to reduce their intrinsic hazards



Discuss the importance of dissolved oxygen in water. How is COD of a polluted water measured?

The chemical oxygen demand (COD) is a measure of water and wastewater quality. The COD test is often used to monitor water treatment plant efficiency. This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to carbon dioxide. The COD is the amount of oxygen consumed to chemically oxidize organic water contaminants to inorganic end products.

The COD is often measured using a strong oxidant (e.g. potassium dichromate, potassium iodate, potassium permanganate) under acidic conditions. A known excess amount of the oxidant is added to the sample. Once oxidation is complete, the concentration of organics in the sample is calculated by measuring the amount of oxidant remaining in the solution. This is usually done by titration, using an indicator solution. COD is expressed in mg/L, which indicates the mass of oxygen consumed per liter of solution.


Define pollution. Give an account of environmental pollutants. Describe their sources and suggest suitable methods of control of air pollution.

Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants.
Environmental pollution is the introduction of harmful materials caused by pollutants into the environment. Pollutants are the various impurities that have found their way into the environment due to both human activity and natural causes thus leading to pollution.

Hydrocarbons (HCs) also called Volatile organic compounds (VOCs)

Types: Methane $$(CH_4)$$, Butane $$(C_4H_{10})$$, Ethylene $$(C_2H_4)$$, Benzene $$(C_6H_6)$$, Propane $$(C_3H_8)$$

Sources of Production: Evaporation from gasoline tanks, carburettors; burning of fuels; biomass; municipal lard fills; microbial activity of sewage; industrial process involving solvents changes that occur in.

Effects on Humans and Environment: Can have carcinogenic effect on humans; higher concentrations are toxic to plants and animals; can convert into harmful compounds through complex chemical atmosphere; some are more reactive with sunlight and produce photochemical smog.


Oxides of Nitrogen $$(NO_x)$$

Type: Nitrogen oxide $$(NO)$$; Nitrogen dioxide $$(NO_2)$$; Nitrous oxide $$(N_2O)$$ ; Nitrate $$(NO_3)$$

Sources of Production: Burning of fuels; biomass burning; by product in the manufacturing of fertilizers

Effects on Humans and Environment: Form the secondary pollutants: peroxy acetyl nitrate (PAN) and nitric acid $$(HNO_3)$$; suppression of plant growth and tissue damage; cause irritation to eyes, viral infections like influenza; nitrate form in atmosphere impairs the visibility whereas in soil promotes the plant growth.


Oxides of sulphur $$(SO_x)$$

Types: Sulphur dioxide $$(SO_2)$$; Sulphur trioxide $$(SO_3)$$; Sulphate $$(SO_4)$$

Sources of Production: Combustion of sulphur containing fuel e.g., coal, petroleum extraction and refining; paper manufacturing; municipal incinerating; ore smelting for metal extraction

Effects on Humans and Environment: $$SO_2$$ has maximum deleterious effects as it damage to human and other animal lungs and is important precursor to acid rain; adverse effects include corrosion of paint, metals and injury or death to animals and plants.


Oxides of Carbon $$(CO_x)$$

Types: Carbon dioxide $$(CO_2)$$, Carbon monoxide $$(CO)$$

Sources of Production: Combustion of coal, oil and other fuels for energy production manufacturing and transport Biomass burning.

Effects on Humans and Environment: $$CO_2$$ has a major role in green-house effect, produces weak carbonic acid adding to acid rains; $$CO$$ affects human health by binding to hemoglobin, which may result in asphyxia; hemoglobin has 250 times more affinity with $$CO$$ as compared to that of
$$O_2$$.


Other organic compounds

Types: Chlorofluoro carbon $$(CFCs)$$, Formaldehyde $$(CH_2O)$$, Methylene chloride $$(CH_2Cl_2)$$, Trichloro Ethylene $$(C_2HCl_3)$$, Vinyl chloride $$(C_2H_3Cl)$$, Carbon tetra chloride $$(CC1_4)$$, Ethylene Oxide $$(C_2H_4O)$$

Sources of Production: Aerosol sprays; foam and plastics for making disposable fast food containers; refrigeration

Effects on Humans and Environment: CFCs cause reduction in stratospheric ozone that allows greater penetration of ultraviolet light at earth surface; intensified UV radiations cause skin cancer and can have lethal effects on various; life forms.


Metals and other inorganic Compounds

Types: Lead $$(Pb)$$, mercury $$(Hg)$$, Hydrogen sulphide $$(H_2S)$$, Hydrogen Fluoride $$(HF)$$

Sources of Production: Oil wells and refineries; transport vehicles; municipal landfills; fertilizer, ceramic, paper, chemical and paint industries pesticides; fungicides; aluminium production; coal gasification

Effects on Humans and Environment: Cause respiratory problems, toxicity and even death to humans and other animals; damage to crops; prove to be carcinogenic.


Liquid droplets

Types: Sulphuric acid $$(H_2SO_4)$$, Nitric acid $$(HNO_3)$$ –Oil, Pesticides e.g. DDT and Malathion

Sources of Production: Agriculture pesticides; fumigation; oil refineries; reactions of pollutants in the atmosphere


Suspended particulate Matter (SPM-solid Particles)

Types: Dust, soil, sulphate Salts, heavy metal salts, Fire particles of carbon (soot), silica, asbestos, Liquid sprays, mist etc.

Sources of Production: Fuel combustion; building constructions; mining; thermal power stations; stone crushing; industrial processes; forest fires; refuse incineration.

Effects on Humans and Environment: Have chronic effects on respiratory system; deposition on the surface of green leaves thus interfering with absorption of $$CO_2$$ and release of $$O_2$$; blocking of sunlight; particles size that range between 0.1 to 10um, cause greatest lung damage


Some of the effective methods to Control Air Pollution are as follows:


Source Correction Methods:

Industries make a major contribution towards causing air pollution. Formation of pollutants can be prevented and their emission can be minimised at the source itself. By carefully investigating the early stages of design and development in industrial processes e.g., those methods which have minimum air pollution po­tential can be selected to accomplish air-pollution control at source itself.


Pollution Control Equipment:

Sometimes pollution control at source is not possible by preventing the emis­sion of pollutants. Then it becomes necessary to install pollution control equip­ment to remove the gaseous pollutants from the main gas stream.

The pollutants are present in high concentration at the source and as their distance from the source increases they become diluted by diffusing with envi­ronmental air.


Fabric Filters (Baghouse Filters):

In a fabric filter system, a stream of the polluted gas is made to pass through a fabric that filters out the particulate pollutant and allows the clear gas to pass through. The particulate matter is left in the form of a thin dust mat on the insides of the bag. This dust mat acts as a filtering medium for further removal of particulates increasing the efficiency of the filter bag to sieve more sub mi­cron particles

Electrostatic Precipitators:

The electrostatic precipitator works on the principle of electrostatic precipitation i.e. electrically charged particulates present in the polluted gas are separated from the gas stream under the influence of the electrical field.


Wet Collectors (Scrubbers):

In wet collectors or scrubbers, the particulate contaminants are removed from the polluted gas stream by incorporating the particulates into liquid droplets.



What are the major sources of water pollution? Discuss the nature of the pollutants involved and suggest methods of control.

Water pollution occurs when harmful substances—often chemicals or microorganisms—contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment.

Sources of Water Pollution

This section gives information about the most significant sources of water pollution.

Sewage (Waste Water)

Sewage is another name for waste water from domestic and industrial processes. Despite strict regulatory control, the Environment Agency data shows that the water and sewage industry accounted for almost a quarter of the serious water incidents in England and Wales in 2006.

Agricultural Pollution

The agriculture industry covers 76% of the land area of England and Wales. Agricultural processes such as uncontrolled spreading of slurries and manure, disposal of sheep dip, tillage, ploughing of the land, use of pesticides and fertilisers can cause water pollution. Accidental spills from milk dairies can also affect the quality of water.

Oil Pollution

Every year there are about 3,000 pollution incidents involving oil and fuels in England and Wales. Oil spillages affect water quality in a number of ways. Oil can make drinking water unsafe to drink. A substantial amount of oil released into oceans and seas will destroy wildlife and the ecosystems that sustain them. Oil spills also reduce oxygen supplies within the water environment. The main causes of oil related water pollution are:

  • loss from storage facilities
  • spillage during delivery and;
  • deliberate disposal of waste oil to drainage systems

Radioactive Substances

Radioactive waste is another source of water pollution. Radioactive substances are used in nuclear power plants, industrial, medical and other scientific processes. They can be found in watches, luminous clocks, television sets and x-ray machinery. There are also naturally occurring radioisotopes from organisms and within the environment. If not properly disposed of, radioactive waste can result in serious water pollution incidents.

River dumping

Lots of people dump supermarket trolleys, bicycles, garden cuttings and electronic waste into rivers or river banks. This is illegal and offenders may be charged for fly-tipping if caught. River dumping not only causes water pollution; it also harms wildlife and increases the risk of flooding. Fly-tipping (this includes river dumping) is a criminal offence. In the most severe cases, it can attract a maximum fine of £50,000 or a 5 year jail term.

Marine Dumping

The Worldwide Fund for Nature (WWF) estimates that a staggering amount of waste enters into the sea every year. Part of this is due to deliberate dumping of waste into coastal waters. Other sources of waste at sea include plastics and other materials blown or washed from land. Marine dumping is illegal under international and UK legislation. For more information visit the marine pollution page.

Effects of water pollution

The effects of water pollution are varied. They include poisonous drinking water, poisionous food animals (due to these organisms having bioaccumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants. are varied. They include poisonous drinking water, poisionous food animals (due to these organisms having bioaccumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants.

Methods of control of water pollution

1. Keep out oils, fat, or grease from the sink. Desist from pouring cooking oil, fat or grease down the kitchen sink. Instead, keep a jar that collects all the fats, grease or oil then discard in solid waste.

2. Abstain from flushing contaminated liquids, pills, drugs, or medications down the drain. These substances contain scores of toxic materials that destroy the quality of natural water systems. Instead, use the recommended disposal methods.

3. Desist from using the toilet as a bin. Most people discard dust clothes, paper wastes, synthetic materials, and wrappers in the toilet. The destructive elements of these materials may finally end up in the oceans, lakes or rivers. Desisting from this habit can considerably prevent water pollution.

4. Ensure minimal use of bleach or detergents. During cleaning of laundry or cutleries, it is vital to minimize the use of bleach and detergents. Instead, you can persist on only using phosphate-free detergents and soaps.

5. Reduce the use of herbicides, pesticides, and fertilizers. Excessive use of herbicides, pesticides, and fertilizers leads to water pollution as the chemicals contained in the products often find way into the water systems through surface runoff or infiltration into the soil. Minimizing their usage or using organic methods for pest, weed, and disease control can appreciably reduce water pollution.

6. Proper sewage treatment and management. Proper sewage treatment is required to limit the amount of toxic substances that normally end up in water systems such as lakes, rivers, and oceans. Also, individual homes that use septic tanks or cellar drains need to ensure proper management of their home sewage to avoid pollution.

7. Dispose trash properly. When trash is not disposed properly some of the non-degradable products such as diapers and sanitary towels may end up destroying the process of sewage treatment, especially when they are flushed down the toilet. At times, poor disposal of solid non-degradable materials such as plastics normally ends up littering the beaches and river banks.

8. Avoid direct dumping into water systems. By all means possible, we should desist from disposing rubbish or any other waste products into lakes, rivers, streams or oceans. Still, you can do the best to clean your local water body whenever you notice rubbish littering the beaches or banks.

9. Always conserve water. Play an active role in reducing water pollution by conserving water at all time. You can achieve this by ensuring the taps are always turned off when they are not in use. Conserving water reduces the amount of contaminated water that needs to be treated.

10. Insist on using environmentally safe products. Whenever you purchase household products such as cleaning material, medical supplies, paints, insect/ant repellants, or chemical substances; always persist on obtaining and using products that are less harmful to the environment.

11. Practice tree planting. Planting trees reduce the speed of surface water runoff and as such, lessens erosion and prevents toxic substances and chemicals from washing into water systems. If you live next to a water body, please take this initiative today and plant trees and vegetation covers such as flowers, grass, and shrubs.

12. Re-use automobile oil as much as possible and keep your vehicle well maintained. Re-using automobile oil reduces the amount of used oil that is discarded which may end up polluting water bodies. Also, it is essential to keep your vehicle well maintained so as to prevent the leakage of deadly fluids like oil and antifreeze.

13. Support green-oriented companies. These are the companies that take creative initiatives to reduce water pollution. For instance, some green cleaning product companies make the packaging materials by using recycling plastics collected from the oceans. Also, some sewage treatment firms now clean wastewater without the use of chemicals. Supporting and using the services of such companies can greatly help reduce water pollution.

14. Use super energy saving washing machines. When purchasing washing machines, ensure you buy energy star approved washing equipment which can save energy and up to 60 liters of water. Eventually, it reduces the amount of wastewater that needs treatment.

15. De-clog your drains naturally. The typical drain cleaners contain several noxious chemicals such as sodium hydroxide. You can instead use natural methods such as pouring equal portions of white vinegar, boiling water and baking soda and let it stay in the drain for 30 minutes before rinsing.

16. Always opt for recyclable and reusable options. Reusable and recycled materials avoid the unnecessary use of water. By using these options, it, therefore, means you are conserving water. At the same time, you are minimizing the amount of waste water produced during production and processing. This should also include re-using dishware and linens such as towels and bed sheets.

17. Skip the use of plastics. Plastic leftovers such as used plastic water bottles, disposable plastic plates, and plastic bags frequently end up in the oceans, lakes, streams and rivers, contaminating natural habitats and destroying aquatic life.



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

Yes, we can easily observe the soil pollution in our neighborhood which is mainly carried out by the industrial wastes and agricultural pollutants like pesticides and fertilisers. It can be controlled by the following methods:

  • Excessive use of insecticides and pesticides should be avoided.

  • Insecticides like DDT are insoluble in water. Due to which, they remain in soil for a long time, contaminating the root crops.

  • The use of polythenes should be avoided.

  • Non-biodegradable waste should be recycled rather than burying in the soil or burning.

  • Household waste, biological waste and chemical waste is often incinerated. Incineration greatly reduces waste volume.



How should the management of domestic and industrial wastes be done?

Domestic waste is waste that is generated as a result of the ordinary day-to-day use of a domestic premise. The management of domestic waste can be done by following methods.

  • Source Reduction and Reuse

This is the strategy most commonly used by governments and local authorities. Reducing waste at the source is achieved by expanding recycling efforts through creating recycling networks and providing on-site food waste treatment facilities at residential and commercial properties. The objective is to reduce the heavy reliance on raw materials that are continuously getting depleted, in an effort to conserve the environment.

  • Recovery and Recycling

Recovery involves the use of discarded items for other meaningful uses. The discarded items usually have to go through a bit of processing to extract or recover resources, or to transform them into usable forms of energy such as fuel, electricity, or heat.

Recycling, on the other hand, involves converting trash into new products to reduce the production of fresh materials and conserve energy. Recycling is tied to the first point of source reduction, and is the third component of the waste management hierarchy: Reduce, Reuse, Recycle. In addition to reducing the creation of new materials, recycling decreases energy usage, reduces air and water pollution, reduces the volume of trash sent to landfills, and reduces greenhouse gas emissions.

  • Landfills

This is the most common waste disposal method today. It involves burying trash in the land while taking measures to eliminate both odours and the risk of toxic substances seeping into the ground and contaminating water sources. With the strong presence of landfill gases such as methane, and land scarcity, many garbage removal companies are considering other options.

  • Combustion/Incineration

Municipal solid wastes that cannot be recycled are burned at high temperatures to reduce its volume by up to 80 percent. This means that the residue occupies 20 to 30 percent of the landfill space that would have been occupied by the solid waste, reducing the stress on landfills. Also referred to as thermal treatment, this method can also be used to generate heat, gas, and steam for power.

  • Composting

This is a natural bio-degradation process of organic wastes (kitchen waste and plant remains) that converts them into nutrient-filled food for plants. This is a common technique in organic farming, where the organic materials sit in one place for months to allow for decomposition


Industrial waste is the unwanted byproduct of industrial processes. These processes include mining and manufacturing activities. Therefore, industrial waste management is the act of safely removing and disposing of industrial waste. Some of the strategies that can utilize to manage industrial wastes are:

  • Segregation and Recycling

Much of the waste that is generated by your company’s production, shipping, and packaging needs is not reusable or compostable, but it is recyclable. The first step in your industrial waste management program is to identify which items can be recycled, and set up recycling bins or dumpsters into which they can be sorted. Most recycling centers can handle glass, paper, and plastic recycling. Many can also handle scrap metal recycling, cardboard recycling, food waste recycling, and electronics recycling. You must segregate and separate your recycling from your hazardous waste, compostable waste, and non-hazardous solid waste.

  • Use of Landfills

Landfills are one of the most common ways to dispose of waste in America. The only waste that should be sent to landfills is that which is non-hazardous, non-recyclable, and non-compostable. When waste is sent to a landfill, it is confined to a small area, compacted when necessary, and then buried in the earth. As the waste decomposes, it releases gases that can be converted to natural gases used for power and fuel. Landfills are cost-efficient and are designed to minimize the harm done to the environment.

  • Composting

The composting process turns organic waste into fertilizer that can be used to nourish plants. Most food waste can be composted, and even unsafe organic items can be turned into safe composting. You can compost food waste, leaves, newspaper, very small pieces of cardboard, straw, and sawdust. Compost is then added to soil to provide nutrients and encourage growth. Composting is one of the most effective ways to reuse and recycle waste.



Write an essay on green chemistry.

Green chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, use, and ultimate disposal. Green chemistry is also known as sustainable chemistry.

Green chemistry:

  • Prevents pollution at the molecular level
  • Is a philosophy that applies to all areas of chemistry, not a single discipline of chemistry
  • Applies innovative scientific solutions to real-world environmental problems
  • Results in source reduction because it prevents the generation of pollution
  • Reduces the negative impacts of chemical products and processes on human health and the environment
  • Lessens and sometimes eliminates hazard from existing products and processes
  • Designs chemical products and processes to reduce their intrinsic hazards


These principles demonstrate the breadth of the concept of green chemistry:

Prevent waste: Design chemical syntheses to prevent waste. Leave no waste to treat or clean up.

Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. Waste few or no atoms.

Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to either humans or the environment.

Design safer chemicals and products: Design chemical products that are fully effective yet have little or no toxicity.

Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If you must use these chemicals, use safer ones.

Increase energy efficiency: Run chemical reactions at room temperature and pressure whenever possible.

Use renewable feedstocks: Use starting materials (also known as feedstocks) that are renewable rather than depletable. The source of renewable feedstocks is often agricultural products or the wastes of other processes; the source of depletable feedstocks is often fossil fuels (petroleum, natural gas, or coal) or mining operations.

Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste.

Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions. Catalysts are effective in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric reagents, which are used in excess and carry out a reaction only once.

Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.

Analyze in real time to prevent pollution: Include in-process, real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.

Minimize the potential for accidents: Design chemicals and their physical forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.



What do you understand by BOD and COD? How are these determined? Which one is preferred?

COD or Chemical Oxygen Demand is the total measurement of all chemicals (organics & in-organics) in the water / waste water; BOD is a measure of, the amount of oxygen that require for the bacteria to degrade the organic components present in water / waste water


Differentiate between afforestation and deforestation


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Explain the strategies which should be adopted to control environmental pollution.

Lots of solid waste is generated in the neighborhood. Apart from household wastes, we also have medical, agricultural, mining and industrial wastes. The improper disposal of these wastes results in environmental pollution. Hence, care must be taken while disposing these wastes to reduce the pollution levels in our surroundings.

Recycling

This is the simplest method of treating the waste. Recycling of materials saves much of the raw materials cost as well as reduces the cost of disposal. Some common examples of recycling by industries are:

  • Recycling of Glass
  • Using scrap metal to manufacture steel
  • Recovering energy by burning down of wastes which are combustible in nature
  • The use of waste paper.

Sewage treatment

Sewage treatment involves the following three types of stages

  • The first stage known as Primary Treatment involves the removal of large solid particles. This is done by mechanical process consisting of screening and sedimentation. For this, the waste is filtered through different types of screens. In the next step solid waste is separated and then dumped in landfill sites. It is then allowed to flow into sedimentation tanks. This process allows removal solid that settles out (sludge). This process also allows removal of grease which floats to the surface and can be skimmed off.
  • The second stage known as secondary treatment involves the biological oxidation of organic content of waste materials by micro-organisms followed by filtration.
  • In the third step which is also called as final treatment which includes various specialized physical and chemical processes that help in reducing the quantities of specific pollutants that remain in the sewage even after primary and secondary treatments. The quality of wastewater is improved after this process. The common methods used in this treatment involve reverse osmosis, disinfection by chlorine, treatment with activated charcoal, coagulation, filtration, chemical removal of phosphate, etc.


During these operations sludge is produced which also poses a problem for safe disposal. The sludge is dried and then damped or digested or may be incinerated



Why does water covered with excessive algae growth become polluted ?

Presence of excessive growth of algae shows that water contains lot of phosphate due to the inflow of fertilizers from the surroundings. The decomposition of algae produces bad smell and unattractive appearance making it unfit for swimming, boating etc. and concentration of dissolved oxygen also decreases which may be harmful for aquatic life.


Ozone is a gas heavier than air. Why does ozone layer do not settle down near the earth ?

Ozone is thermodynamically unstable and decomposes into molecular oxygen. Thus, a dynamic equilibirium exists between the production and decomposition of ozone.

$$O_2(g) \overset{UV}{\longrightarrow} O(g) + O(g)$$
$$O(g) + O_2 \overset{UV}{\rightleftharpoons } O_3(g)$$


Ozone is a toxic gas and is a strong oxidising agent even then its presence in the stratosphere is very important. Explain what would happen if ozone from this region is completely removed ?

  • Atmosphere is divided into certain levels like atmosphere, troposphere, stratosphere, exosphere. The stratosphere consists of considerable amount of ozone $$(O_3).$$

  • It protects us from the harmful ultraviolet (UV) radiations $$(\lambda \,255\,nm)$$ coming from the sun. These radiations cause skin cancer (melanoma) in humans. Therefore, it is important to maintain the ozone shield.

  • The main reason of ozone layer depletion is believed to be the release of Chlorofluorocarbon (CFCs), also known as Feron. 

  • UV radiation is also one of the cause of cataract formation in eyes. It can cause genetic mutation and destroy crops, aquatic plants and animals are also affected by UV radiations.


What are the point sources of water pollution?

The point source is easily identifiable and a single source of pollution. 
For example, sewage treatment plants.


What is the importance of measuring BOD of a water body ?

The amount of BOD in water is a measure of the amount of organic material present in water, in terms of how many oxygen will be required to break it down biologically. Clean water would have BOD value less than 5 ppm whereas highly polluted water has BOD value 17 ppm or more.


Name any two :
Natural sources of atmospheric pollution.

Decay of plants and animals
Disintegration of rocks and soil


Define the following terms 
Pollution 

Presence or introduction of harmful or poisonous substance into environment is called as pollution.


List the advantages of 'reduce' and 'reuse' to save environment.

It is useful for people because many people gets benefit from items which are reused and recycled. These are cheaper methods. They need less space. We should minimize the use of various product which are obtained directly or indirectly from natural resources. We can save electricity by switching off fans and lights.


Answer in brief: Why is tap water a mixture?

Tap water contains minerals, air, chlorine and other dissolved impurities that varies from place to place, therefore it is a mixture.


What are the components of clean , dry air ?

Pure Air Components By Volume (% Proportion)Concentration (ppm)
Nitrogen$$ 78.09 $$$$ 780900 $$ 
Oxygen $$ 20.94 $$$$ 209400 $$
Inert gas 
Argon $$ 0.93 $$$$ 9300 $$
Neon$$ 18 $$
Helium $$ 5 $$
Krypton $$ 1 $$
Xenon $$ 1 $$
Carbon dioxide $$ 0.03 $$$$ 315 $$
Methane $$ 1 $$
Hydrogen $$ 0.5 $$
Natural pollutants 
Oxides of Nitrogen$$ 0.52 $$
Ozone $$ 0.52 $$


Explain the effect of sulphur dioxide on the atmosphere.

Effects of Sulphur dioxide on the atmosphere are as follows
  • It destroys vegetation and weakens building materials and constructions
  • It mixes with the smoke to form smog, which is harmful to the environment and living beings.
  • Sulphur dioxide combines with atmospheric oxygen to form Sulphur trioxide, which causes acid rain.


What are the main causes of water pollution? How can it be controlled?

Main causes of water pollution are:
1. Chemical waste, industrial waste and agricultural process.
2. Thermal waste from nuclear and thermal power plants.
3. Sewage and garbage.

Prevention of water pollution:
1. Domestic sewage should be treated before being discharged into rivers. 
2. Use of non-biodegradable substances like detergents should be stopped.
3. Trees and plants must be planted along the banks of rivers.
4. Purification of water bodies should be carried out.
5. The waste products of industries should be treated before they are discharged into rivers.


State the sources and effects of the following gases :
Water vapour 

Water vapour
  • Burning of hydrocarbons


How can you apply green chemistry for the following:
   To avoid use of halogenated solvents in dry cleaning and that of chlorine in bleaching.

Organic solvents such as benzene, toluene, carbon tetrachloride etc., are highly toxic. One should be careful while using them. For bleaching the cloth $$H_2O_2$$ can be used which is not harmful. Earlier, $$Cl_2$$ was used for bleaching the cloth.


Define pollution.

The introduction of harmful agents into the enviroment is called pollution.


Describe the methods of saving ozone layer .

Following are the methods to protect the Ozone layer
  • Using alternative products such as HCFCs (hydrochlorofluorocarbons)
  • Montreal Protocol, an international treaty, helps prevent ozone depletion. 


Which radiations are absorbed by atmospheric gas?

Infrared radiations are absorbed by atmospheric gas that keeps earth warm.


Besides air pollution, what are the problems that may arise when garbage is heaped? Discuss and record. 

The problems caused by garbage heap are:
• Soil contamination 
• Air contamination 
• Water contamination 
• Bad impact on human health 
• Impact on animals and marine life. 
• Disease-carrying pests 
• Adversely affect the local economy 
• Missed recycling opportunities. 


Define an environmental pollutant. What do you understand by an environmental pollution model?

The substance which causes an 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 land by man. Some of the pollutants may be absorbed or chemically changed by the environment; the rest build-up to concentration which are harmful to the environment. 


The pollutants such as $$ NO_2 , SO_2 $$ and $$ SO_3 $$  dissolved in the moisture of air are the cause of __________ .

The pollutants such as $$ NO_2 , SO_2 $$ and $$ SO_3 $$  dissolved in the moisture of air are the cause of acid rain.


Afforestation helps in soil______.

Afforestation helps in soil $$ conservation $$


What steps does government introduced to stop the air pollution in Delhi?

A number of steps were introduced by the government to reduce the pollution. These includes:
1. Use of unleaded petrol.
2. Adopting Euro-II standards
3. Use of CNG in place of diesel and petrol in public transport system. These measures have drastically reduced air pollution and made Delhi a cleaner city in terms of air quality.


What is COD? Which chemical substance is generally used in its measurement? 

COD stands for Chemical Oxygen Demand. It is measured by treating the given sample of water with an oxidizing agent, generally $$K_2Cr_2O_7$$ in presence of dilute $$H_2SO_4$$.


Name any four methods for waste management.

Recycling, burning, incineration, sewage treatment and dumping are methods for waste management.


What do you mean by “inversion temperature” in different regions of the atmosphere?

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.


Which zone is called the ozonosphere?

Stratosphere zone is called the ozonosphere.


Define environmental pollution. List three episodes of the recent past of environmental pollution.


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What are the different sources of soil pollution? Name the pollutants being added by them.


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Why COD is preferred over BOD?

COD is preferred over BOD because COD can be found in a few minutes whereas BOD requires at last $$5$$ days.


"Oxygen plays a key role in the troposphere while ozone ln the stratosphere". Elucidate.

All biological activity takes place in the troposphere for which oxygen is required. Ozone in the stratosphere absorbs the harsh ultraviolet radiation coming from the sun which otherwise causes skin cancer, affects thecornea of the eye and may cause even blindness. 


Fish do not grow as well in warm water as in cold water. Why?

The amount of dissolved oxygen in warm water is less than in cold water so fish do not grow as well in warm water as in cold water. 


Quote three incidents which proved disastrous due to environmental pollution. How can you classify environmental pollutants and environmental pollution into different types?


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How is ozone formed in the stratosphere?


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Why is use of excess fertiliser detrimental for environment?

Use of excess fertilisers will cause:
i) Mineral loading of underground water.
(ii) Excess minerals in the crop plants.
(iii) Salination of soil.
(iv) Run off from fertilizers rich soil, will cause eutrophication of water bodies.


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

UV radiations act on dioxygen to form ozone.
There is dynamic equilibrium between the production and decomposition of ozone. The disturbance of this equilibrium results in ozone depletion.
Chlorofluorocarbons mix with atmospheric gases and reach the stratosphere, where they are decomposed by UV rays to produce chlorine free radicals.
These chlorine free radicals react with ozone to form oxygen and $$\displaystyle ClO \cdot $$ free radicals which react with atomic O to produce more chlorine free radicals.
This results in continuous breakdown of ozone present in the stratosphere damaging the ozone layer.
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Match the following sources of soil contamination.

Dredged spoils means improper method of dredging at fertile land, causing soil infertility and leaving the soil more prone to external pollution.
Using of explosives to blow up mines emit toxic byproducts which leak to the ground.
Non-biodegradable rubbles or debris at the demolition and construction sites, which are not cleared, settle in the soil and undergo chemical reactions to increase soil toxicity.
Improper waste disposal system through household, and improper sanitation system, causes waste accumulation.


Describe why stratosphere is important for earth?

The stratosphere has two major features that contribute to the state of Earth's surface. The first is most well known--the stratosphere contains high concentrations of ozone which shields the ground from many high energy photons that would otherwise contribute to plant damage and skin cancer. It's other feature is more subtle--it holds greenhouse gasses in various concentrations, which impact surface temperature and overall climate. The particular importance of greenhouse gasses in the stratosphere is that they are long lived. The stratosphere is very stable, and its composition changes on the order of decades vs months in the troposphere. The potential for long-term effects from changes in the stratosphere is great--a particularly well known example is the release of CFCs that continue to deplete ozone over 50 years after their original release.


Match the Column I and Column II and pick the correct matching from the codes given below.

  1. Photochemical smog consists of primary and secondary pollutants. Primary pollutants consist of nitrogen oxides and volatile organic compounds, whereas secondary pollutants consist of Peroxy acetyl nitrate and ozone.
  2. Aromatic hydrocarbons containing two or more fused rings are called Polycyclic aromatic hydrocarbons. It is found that the number and position of certain groups such as methyl, hydroxide, cyanide, and methoxy in these compounds give rise to carcinogenicity.
  3. IR active molecules such as $$HCl, CO,$$ and $$NO$$ absorb the radiation from the infrared region and causes global warming.
  4. Indigo is a vat dye. Dyeing with indigation was carried out in the wooden vats in the form of water soluble indigotin-white.
  5. Dioxins are a group of chlorinated organic compounds that are formed in Waster Incineration.


Write short notes on,  (a) Biological concentration and magnification,  (b)DDT,  (C) Bordeaux mixture,  (d) IPM,  (e) Natural insecticides,  (f) Biopesticides,  (g) Bioinsecticides

(a) Biological concentration and magnification: Bioconcentration occurs when an organism absorbs toxic substance from only water at a a rate greater than that at which the substance is lost. Bioaccumulation and Bioconcentration are synonymous except the difference of the source. Biomagnification refers to the is the increase in concentration of the POPs such as DDT, that occurs in a food chain as a consequence of persistence, high lipid solubility and low water solubility. 
(b) DDT: Dichlorodiphenyltrichloroethane (DDT), also called 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane is a synthetic insecticide belonging to the family of organic halogen compounds, highly toxic toward a wide variety of insects as a contact poison that apparently exerts its effect by disorganizing the nervous system. 
(c) Bordeaux mixture: Bordeaux mixture is a combination of copper sulfate, lime, and water which is an effective fungicide and bactericide that has been used for decades to control diseases of fruit and nut trees, vine fruits, and ornamental plants. 
(d) IPM: Integrated pest management (IPM), also known as integrated pest control (IPC) is a broad-based approach that integrates practices for economic control of pests. IPM aims to suppress pest populations below the economic injury level (EIL). 
(e) Natural insecticides: Insecticides are substances used to kill insects. Natural insecticides, such as nicotine, pyrethrum and neem extracts, made by plants act as defenses against insects.
(f) Biopesticides: Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides.
(g) Bioinsecticides: Control of insect pests in agriculture and of insect vectors of important human diseases is mainly achieved using chemical insecticides. In bioinsecticides, microbial agents are used to make the plant susceptible to any insect that invades the plant.


The spores of Bacillus thuringiensis are used as bioinsecticide. Comment.

Bacillus thuringiensis is a bioinsecticide, used to  kill larval forms of many insect pests, small wasps so they are used as bio-control agents. It alters the physiological, hormonal balance of the insects thus promoting their killing.


How have human activities caused desertification? Explain.

Desertification refers to the conversion of fertile land into a desert as a result of natural or man's activities. Human activities like overuse of land to the point that it loses its fertility and causes desertification are known.
These activities include repeated crop cultivation or agriculture on the same patch of land, poor irrigation practices, overheating by livestock, use of synthetic or inorganic fertilizers, overpopulation, deforestation, industrialization etc.
Desertification can only be tackled through proper land management system or the land would enter this irreversible state where all its productivity is lost forever.


A Crane had DDT level of 5 ppm in its body. What would happen to the population of such birds?

Some toxic substances aren't metabolized or excreted from an organism's body. This leads to an accumulation of these intoxicants at successive trophic levels, this is called as biomagnification. In a crane having 5 ppm of DDT concentrated in its body, calcium metabolism is disrupted. This causes thinning and weakening of eggshells and premature breaking of eggs resulting in a significant decrease in their population.


Define the following terms:
a) Malathion
b) Simazine 
c) Disulfoton

a) Malathion is an insecticide. It belongs to the family organophosphates. It is used for mosquito control and fruit fly eradication.
b) Simazine is an herbicide. It belongs to class triazine. It is used for weed control and control of annual grasses.
c) Disulfoton is an insecticide. It also belongs to family organophosphate. It is used as pesticide to control harmful pests that attack field and vegetable crops. 


A little amount of fertilizer makes your lawn grow better but a larger amount of the same kills grasses. Why?

  • When fertilizers are used excessively or applied in large amounts it leads to fertilizer burns.
  • Nitrogen and salt levels in the soil increases that kill grasses.
  • Salt build-up in the soil causes drying, i.e the grasses turn yellow or brown .


Define a) Dalapon b) Metolachlor

a) Dalapon is a herbicide. It is used to control perennial grasses. It is used in the field of sugarcane and sugar beets. 
b) Metolachlor is a herbicide. It belongs to the chloroacetanilide family of herbicides. It is used to control grass and broad leaf weeds.


Name any four gaseous pollutants.

Hydrogen sulphide, Carbon monoxide Nitrogen oxide, Sulphur dioxide.


Fill in the blanks in the following: 
A lead compound known as ...... is used as an antiknock in the petroleum industry to increase the efficiency of fuel consumption.

A lead compound known as tetra ethyl lead (TEL) is used as an antiknock in the petroleum industry to increase the efficiency of fuel consumption.


Describe the following in brief:
Ozone deletion over Antarctica (do not write reaction)

Ozone deletion 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 stratospheric coulds are formed over Antarctica. These clouds provide surface on which chlorine nitrate molecules   formed gets hydrolysed to from HOClHOCl. It also reacts with HClsHCls to give Cl2Cl2. When sunlight returns to Antarctica again ozone depletion starts by free radicals.


How can you apply green chemistry for the following:
   To reduce the consumption of petrol and diesel.

In place of petrol and diesel oil the use of CNG and LNG has been preferred because they cause less or no pollution. The other sources such as $$H_2, C_2H_5OH,$$ etc. can also be used in place of petrol and diesel.


A farmer using pesticides on his farm. He used the produce of his farm as food for rearing fishes. He was told that fishes were not fit for human consumption because large amount of pesticides had accumulated in the tissues of fishes. Explain how did this happen ?

Pesticides are basically synthetic toxic chemicals with ecological repercussions. Most of the organic toxins are water insoluble and non-biodegradable. These high persistent toxins are, therefore, transferred from lower tropic level to higher tropic level through food chain. Over the time, the concentration of toxins in higher animals reach a level which causes serious metabolic and physiological disorders.


Answer the following question in your own words.

Which precautions will you take during the spraying of pesticides?

Pesticides are chemicals that are used on plants for protecting them against pest infection. They contain various kinds of chemicals that are harmful to humans as well as the environment. There are certain points that should be taken care of while using pesticides like, cover the nose, mouth, and eyes while spraying them, keeping them out of the reach of children. Another important point is to prevent excessive use of pesticides as they also lead to water and soil pollution. Instead one should adopt natural or biological methods to ward off pests. 


What is Green Chemistry and what are its contributions in prevention of pollution?

Green Chemistry: Green Chemistry is an area of Chemistry and Chemical Engineering focussed on the designing of products and processes that minimizes the use and generation of hazardous substances. It is also known as Sustainable Chemistry.
Green Chemistry was proposed in 1990 to control environmental pollution. According to Green Chemistry, the use of such chemical, reactants, solvents etc, should be encouraged which are not hazardous to human beings
Contributions of Green Chemistry in Prevention of pollution: Green Chemistry is the Philosophye of Chemistry whose aim is to modify present in order to prevent problems in the future. It plays an important role in prevention of pollution. Some strategies of Green Chemistry which can be adopted are:
Optimisation of balance of global mass in order to minimize waster
Minimisation of energy consumption, eg. designing process at ambient temperature and pressure.
Whenever possible replacement of old compounds with others which maintain their functional efficiency while minimizing their toxic impact on the environment and human health
Some aqueous and non-aqueous solvents should be developed which are not harmful for human being and also do not cause environmental pollution
Use of biodiesel and hydrogen in vehicles should be encouraged
To release the minimum amount of wastes
Green chemistry is a new field but it has significant achievement in control of pollution. By using green chemistry we can prepare a prototype of any chemical reaction and can study the used chemical and properties of products
When a chemical reaction is carried out in ultraviolet light. Sound wave and microwave then use get positive output. Nowadays enzymes is used as a catalyst in the manufacturing of antibiotics. Some organic solvent is formed by using green chemistry that are harmful to human health nor the cause of pollution
$${SO}_{2}$$ can be reduced to sulfur by using green chemistry so that air pollution can be reduced
$$C+{SO}_{2}\xrightarrow [  ]{ { 800 }^{ o }C } {CO}_{2}+S$$
$${SO}_{2}$$ gas can be absorbed by using limestone
$$2Ca{CO}_{3}+2{SO}_{2}+{O}_{2}\rightarrow 2Ca{SO}_{4}+2{CO}_{2}$$
In green chemistry, zeolite-based detergent is used which reduces pollution. Now $${CO}_{2}$$ is used for the packing of foam sheet in place of chlorofluorocarbon
Similarly, research are carried out to use helium in place of petrol and diesel to stop pollution caused by motor vehicle
A various method to produce agriculture chemicals is discovered in which we can use poisonous material like cyanide, formaldehyde etc


What chemical reactions are occurring in the stratosphere?


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Discuss about 'Ozone Depletion and its solution'.


Ozone is present mostly in the stratosphere of the atmosphere. Atmosphere oxygen dissociated on absorption of high energy ultraviolet radiation. The oxygen atoms thus formed combine together to form $$O_3$$ molecule

Ozone absorbs low energy ultraviolet radiations and decomposes back to oxygen as a result of this cyclic process the level of ozone remains constant. In the atmosphere.
The energy required for this process is obtained from the ultraviolet process is obtained form the ultraviolet radiations emitted by the sun. Due to this such harmful radiations doe not reach the earth excessively.

Chlorofluoro carbons are responsible for the depletion of the ozone layer. Chlorofluorocarbons released into the atmosphere reach the chlorine the chlorine decomposes ozone molecules into oxygen. This disturbs the equilibrium in the ozone-oxygen cyclic process. Hence the depletion of ozone in the atmosphere reduces the absorption of ultraviolet rays

Today the use of CFC is being controlled in most of the countries. Harmful CFC are replaced nowadays with safer substances this has helped in reducing the rate of depletion of ozone layer
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What are Polar Stratospheric Clouds (PSCs)?

The special types of clouds present over Antarctica in winter are called Polar Stratospheric Clouds.


How to reduce the rate of depletion of ozone layer?


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What is the role of dichloroethane and dibromoethane when added to gasoline along with tetraethyl lead?

The role of dichloroethane and dibromoethane when added to gasoline along with tetraethyl lead is to convert $$PbO$$ produced into volatile $$PbCl_2$$ and $$PbBr_2$$.


What is anoxia or asphyxiations?

Acute oxygen starvation in the body (due to CO poisoning) is called anoxia or asphyxiations.


Name three methods generally used in green chemistry.

Use of sunlight and microwaves, use of sound waves and use of enzymes are the methods generally used in green chemistry.


What do you understand by (i) polar stratospheric clouds (ii) polar vortex?


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Give three examples in which green chemistry has been applied.


(i) In dry cleaning, use of liquefied $$CO_2$$ in place of tetrachloroethene $$(Cl_2C=CCl_2).$$
(ii) In bleaching of paper using $$H_2O_2$$ in place of chlorine.
(iii) In the manufacture of chemicals like ethanal using environment-friendly chemicals and conditions.


COD is found by using______.

  • The chemical oxygen demand (COD) is a measure of water and wastewater quality. The COD test is often used to monitor water treatment plant efficiency. This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to carbon dioxide. The COD is the amount of oxygen consumed to chemically oxidize organic water contaminants to inorganic end products.
  • The COD is often measured using a strong oxidant (e.g. potassium dichromate, potassium iodate, $$\text{potassium }$$$$\text{permanganate}$$) under acidic conditions.


Give some examples of the achievements of green chemistry.


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What do you understand by (i) Mists (i) Smoke (iii) Fumes and (iv) Dust?


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How does oxygen reach water? How is the oxygen content of a sample of water measured?


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Comment on the statementGreen chemistry is an alternative tool for reducing pollution.


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Class 11 Medical Chemistry Extra Questions