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Karnataka 1st PUC Chemistry Question Bank Chapter 14 Environmental chemistry
What is environmental pollution?
Environmental pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings.
What is pollutant?
Any substance which causes pollution is called pollutant.
What are degradable pollutants? Give examples.
The pollutants which rapidly break down by natural processes are called degradable pollutants.
Examples: Vegetables waste, waste papers etc.
What are non degradable pollutants? Give examples.
The pollutants which are not breakdown or slowly degradable by natural processes and remain in the environment in an unchanged form are called non degradable pollutants.
Examples: DDT, some polymers, heavy metals, nuclear wastes etc.
What is troposphere?
The lowest region of atmosphere in which the human beings along with other organisms live is called troposphere.
What is stratosphere?
The layer above the troposphere from 10 to 50 km (from sea level) is called stratosphere.
What are components present in stratosphere?
Stratosphere contains N2, O2, O3 and little water vapour.
In which region of the atmosphere strong air movement and cloud formation occurs?
How does tropospheric pollution occurs?
Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air.
Give examples for gaseous air pollutants.
Oxides of sulphur, nitrogen and carbon, H2S, hydrocarbons, ozone and other oxidants.
Give examples for particulate pollutants.
Dust, mist, fumes, smoke, smog, etc.
What are the sources and harmful effects of oxides of sulphur in the environment?
Oxides of sulphur are produced when sulphur containing fossil fuel is burnt.
Sulphur dioxide is a poisonous gas which causes respiratory diseases like asthma, bronchitis, emphysema in human beings. It also causes irritation to the eyes resulting in tears and redness. High concentration of SO2 leads to stiffness of flower buds which tall off from plants.
Note: SO2 oxidises to SO3 in the presence of particulate matter in polluted air.
Examples 2SO2(g) + O2(g) → 2SO3(g)
SO2 + O3 → SO3 + O2
SO2 + H2O2 → H2SO4
What are the sources and harmful effects of oxides of nitrogen in the atmosphere?
Dinitrogen and dioxygen (main constituents of air) combine together at high altitudes during lightning to form oxides of nitrogen. When fossil fuel is burnt in an automobile at high temperature, NO and NO2 are formed.
2NO + O2 → 2NO2
Rate of production of NO2 is faster when nitric oxide reacts with ozone in the stratosphere.
NO + O3 → NO2 + O2
- The irritant red haze in the traffic and congested places is due to oxides of nitrogen.
- High concentrations of NO2 damage the leaves of plants and retard the rate of photosynthesis.
- NO2 is a lung irritant that can lead to an acute respiratory disease in children and toxic to living tissues.
- NO2 is also harmful to various textile fibers and metals.
Give the sources and harmful effects of hydrocarbons in the atmosphere.
Hydrocarbons are formed by incomplete combustion of fuel used in automobiles.
- Hydrocarbons are carcinogenic (they cause cancer)
- They harm plants by ageing, breakdown of tissues and shedding of leaves and flowers.
Give the sources and effects of carbon monoxide in the environment.
Carbon monoxide is produced due to the incomplete combustion of carbon, coal, firewood, petrol etc. Other, sources of carbon monoxide in the atmosphere are automobile exhaust, poorly maintained vehicles etc.
Effects of carbon monoxide:
1. CO binds to haemoglobin of blood to form carboxyhaemoglobin which is about 300 times more stable than oxygen-haemoglobin complex. When carboxyhaemoglobin concentration increases to 3-4% in blood, the oxygen carrying capacity is reduced. Thus oxygen difficiency cause, headache, weak eyesight, nervousness and cardiovascular disorder. This is the reason why people are advised not to smoke.
2. In pregnant women who have the habit of smoking may induce premature birth, spontaneous abortions and deformed babies.
Explain the sources and effects of CO2 in the atmosphere.
CO2 is released in the atmosphere by respiration, burning of fossil fuels, decomposition of lime stone etc. It is also emitted during volcanic eruptions.
Green plants require CO2 for photosynthesis and intern they release O2. Thus CO2 and O2 are balanced in the atmosphere.
But due to deforestation and burning of fossil fuel increases the CO2 level which causes green house effect and global warming.
Note: The percentage of CO2 in atmosphere is 0.03%.
What is global warming?
The warming of earth due to the trapping of sun’s energy by gases such as carbon dioxide, methane, ozone, chlorofluoro carbon (CFC’S) and water vapour in the atmosphere is called global warming.
What are the causes of global warming?
The main causes of global warming are
- A rise in sea level
- Melting of glaciers and polar ice sheets.
- Increase in heat related diseases.
- Increase in growth of parasites and pests.
- Increase in precipitation and decrease in soil moisture content.
- Extinction of some plants and animal species.
What is green house effect? Give examples for green house gases.
Green house effect is the phenomenon in which Earth’s atmosphere traps the heat from the sun and prevents it from escaping into the outer space. Green house gases are CO2, CH4, O3 CFCS (freons) and water vapour. Or Increase in the concentration of CO2 increases the global temperature. This is called green house effect.
How can we reduce the global warming?
We can prevent the global warming by reducing the production of greenhouse gases by
- Minimising the use of fossil fuels
- Using energy efficient devices
- Using recyclable and reusable products
- Reusing the home wastes, newsprint and cardboard
- Planting more and more trees
What is acid rain? Write the respective chemical reactions using the formation of rain.
Acid rain is the rain water containing H2SO4, HNO3 which are formed from the oxides of sulphur and nitrogen present in the air as pollutants.
The air pollutants such as SO2, NO2 etc undergoes oxidation and reaction with water produces H2SO4 and HNO3 which causes acid rain.
2SO2 + O2 + 2H2O → 2H2SO4
4NO2 + O2 + 2H2O → 4HNO3
What are the harmful effects of acid rain?
1. Acid rain decreases the pH of rain water which damages the digestive, respiratory and nervous systems in human beings and cause many diseases.
2. Due to increased acidity of rain water, the aquatic animals like fishes are unable to survive. Just because of acid rains, several lakes in Sweedan and U.S.A have become fishless.
3. The increased acidity of rain water kills micro-organisms such as bacteria and damages blue green algae. This disturbs the ecological balance of the nature.
4. Acid rain is harmful to plants, trees and bushes. It damages their leaves and retards their growth. This is because acid rains leach away the nutrients like potassium, magnesium, calcium etc from soil and makes it short of essential elements.
5. Acid rain reduces the activity of nitrogen fixing bacteria due to loss of fertility of soil.
6. Acid rain has also been reported to reduce the rate of photosynthesis in plants. This affects the growth of plants.
7. Acid rain causes substantial damage to buildings made of marble, lime stone, slate etc. Attack of acid rain on marble is termed as stone leprosy. Due to this, Taj Mahal, a wonderful monument located at Agra, is slowly disfigured and the marble is being disfigured and lusterless.
What are particulate pollutants? Give examples.
These are the minute solid particles or liquid droplets in air. Examples: Smoke particles from fires, dust particles and ash from industries.
What are viable particulates? Give examples.
These are minute living organisms that are dispersed in the atmosphere. Examples: Bacteria, fungi, moulds, algae etc.
What are the effects of fungi?
Human beings are allergic to some of the fungi found in air. They can also cause plant diseases.
Write a note on non-viable particulates.
Non-viable particulates are formed either by breakdown of larger materials or by the condensation of minute particles and droplets. There are four types of non-viable particulates in the atmosphere: Mist, smoke, fumes and dust.
1. Mist: Mist is produced by particles of spray liquids and the condensation of vapours in air. Herbicides and insecticides that miss their targets travel through the air to form mists.
2. Smoke: Smoke is a mixture of small soot particles (solid or liquid) produced by burning and combustion of organic matter. Oil smoke, tobacco smoke and carbon smoke are typical examples of this type of particulate emission.
3. Fumes: Fumes are condensed vapours formed during sublimation; distillation, boiling and several other chemical reactions. Fumes of metals are the well known particulates of this type. Examples of this category also include metallurgical fumes and alkali fumes.
4. Dust: Dust consists of fine particles produced during crushing, grinding and attribution of solid materials. Non- viable dust particulates in the atmosphere consists of ground lime stone, sand tailings from flotation, pulverised coal, cement, fly ash and silica dust.
What are the effects of particulate pollutants?
Air-borne particles such as dust, fumes, mist etc are dangerous for human health. The effects of these pollutants mainly depends on particle size. The particulate particles bigger than 5 microns are likely to lodge in the nasal passages where as particles of about 10 micron enter into the lungs. Lead emitted by vehicles interferes with the development and maturation of red blood cells.
What is smog? Give the types of smog.
Smog is a mixture of smoke and fog.
There are two types of smog.
1. Classical smog: It is a mixture of smoke, fog and sulphur dioxide. It occurs in cold humid places. It is also called reducing smog because it contains reducing mixture.
2. Photochemical smog: This type of smog results from the action of sunlight on the nitrogen oxides and hydrocarbons produced by automobiles and factories. It is also called as oxidising smog because it contains oxidizing mixture.
Explain the formation of photochemical smog.
The formation of photochemical smog involves a series of photochemical branched chain reactions. The major stages are as follows.
- The hydrocarbons and oxides of nitrogen released by automobiles get accumulated in atmosphere.
- Nitrogen dioxide (NO2) thus accumulated in the atmosphere absorbs sunlight in the blue and near ultraviolet region of the spectrum and decomposes into nitric oxide (NO) and atomic oxygen (O).
- The decomposition of NO2 into NO and O is followed by a series of reactions in which NO is converted into NO2 with simultaneous formation of ozone and aldehydes.
- The hydrocarbons present in the atmosphere undergo oxidation to form a number of secondary pollutants such as formaldehyde (CH2 = O), acrolein (CH2 = CH – CH = O), peroxyacyl nitrates (PAN). The secondary
pollutants form haze like aerosols which constitute a photochemical smog known as Los Angeles smog.
The chemical reactions involved can be described in a simplified manner as follows:
NO2 + hv → NO + O
O + O2 ⇌ O3
O3 + NO → NO2 + O2
Photochemical smog increases with increase in concentration of NO2 and hydrocarbons in atmosphere and also with the intensity of sun light.
What are the effects of photochemical smog?
The three main components of photochemical smog are nitrogen oxides, ozone and organic derivatives (such as acrolein, formaldehyde, PAN etc). Each contributes to the hazardous effects of the smog.
- Pungent smelling, smog-produced ozone is known to be toxic. It can cause coughing, wheezing, bronchial constriction and irritation to the respiratory mucous system.
- Rubber has a high affinity for ozone and it is cracked and aged by it.
- Of all components of smog, Peroxyacyl nitrates (PAN) has the highest toxicity to plants, attacking younger leaves and causing ‘bronzing’ and ‘glazing’ of their surfaces.
- Peroxyacyl nitrates and aldehydes found in smog are eye irritants.
- Ozone is also known to cause damage to vegetation and reduction in plant growth and crop productivity.
How can photochemical smog be controlled?
The formation of photochemical smog can be reduced by decreasing the concentrations of nitrogen oxides and hydrocarbons in the atmosphere. This could be achieved by using catalytic converters in automobiles. The catalytic converters reduce the quantity of hydrocarbons and nitrogen oxides in the smoke coming out of the exhaust pipes of automobiles.
Photochemical smog can also be suppressed by certain compounds, which act as free radical traps. When, these compounds are sprayed in the atmosphere, they generate free radicals which readily combine with free radical precursors of photochemical smog.
How ozone (O3) is formed in the atmosphere?
Ozone is formed in the atmosphere by irradiation of atmospheric oxygen by UV radiations.
O2 + hv → O + O
O + O2 + hv → O3(g)
Why do we protect ozone layer in the atmosphere?
Ozone layer protects from harmful ultraviolet (UV) radiations coming from the sun. These radiation cause skin cancer in humans.
What is the main reason of ozone layer depletion?
The main reason of ozone layer depletion is due to the release of chloro fluoro carbon compounds (CFCS)
What are freons? Give any two uses.
Flourochloro carbon compounds (CFCS) are called freons.
Uses: Freons are used in refrigerators, air conditioners, etc.
How freons damages the ozone layer (creation of ozone hole)?
Once CFSs are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. In stratosphere, they absorb the UV radiations and break up liberating free chlorine atom.
The chlorine atom reacts with O3 to form chlorine monoxide (CIO), which further combines with O to give oxygen.
The chlorine radicals are continuously regenerated and cause the breakdown of ozone.
What are the effects of depletion of ozone layer?
Depletion of ozone layer increases the extent of ultraviolet radiations coming to the earth. Ultra violet radiations are very harmful to human beings. The UV radiations
- Cause sun bums, skin ageing, leukemia, cataract of eyes, skin cancer, lung cancer, breast cancer, premature ageing etc.
- Cause DNA breakage, alteration of DNA replication and even death.
- It has also been reported that plant proteins get easily affected by UV radiations which leads to the harmful’ mutation of cells.
- It also increases evaporation of surface water through the stomata of the leaves and decreases the moisture content of the soil.
- Increase in UV radiations damage paints and fibres, causing them to fade faster.
Give the important types of water pollutants and their sources.
|a.||Micro – organisms||Domestic sewage|
|b.||Organic Wastes||Domestic sewage, animal excreta and waste, decaying animals and plants, discharge from food processing factories.|
|c.||Plant nutrients||Chemical fertilizers|
|d.||Toxic heavy metals||Industries and chemical factories.|
|e.||Sediments||Erosion of soil by agriculture and strip mining.|
|f.||Pesticides||Chemicals used for killing insects, fungi and weeds.|
|g.||Radioactive substances||Mining of uranium containing minerals.|
|h.||Heat||Water used for cooling in industries.|
What are the causes of water pollution? Explain.
(i) Pathogens: The most serious water pollutants are the disease causing agents called pathogens. They include bacteria and other organisms that enter water from domestic sewage and animal excreta. Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases.
(ii) Organic wastes: The other major water pollutant is organic matter such as leaves, grass, trash etc.
Excessive phytoplankton growth within water is a cause of water pollution.
(iii) Chemical pollutants: Water is a universal solvent that dissolves many chemicals.
- The water soluble inorganic chemicals that include heavy metals such as cadmium, mercury, nickel etc constitute an important class of pollutants. These metals can damage kidneys, central nervous system, liver etc.
- Acids (like sulphuric acid) from mine drainage and salts from many different sources including raw salt used to melt snow and ice in the colder climates (sodium and calcium chloride) are water soluble chemical pollutants.
- The organic chemicals are another group of substances that are found in polluted water. Petroleum products pollute many sources of water e.g., major oil spills in oceans.
- The organic substances like pesticides that drift down from sprays or runoff from lands and various industrial chemicals like polychlorinated biphenyls, (PCBs) which are used as cleansing solvent, detergents and fertilizers add to the list of water pollutants. PCBs are suspected to be carcinogenic.
- The detergents available are biodegradable but their use can create other problems. The bacteria responsible for degrading biodegradable detergent feed on it and grow rapidly. While growing, they may use up all the oxygen dissolved in water. The lack of oxygen kills all other forms of aquatic life such as fish and plants.
- Fertilizers contain phosphates as additives. The addition of phosphates in water enhances algae growth. The growth of algae covers the water surface and reduces the oxygen concentration in water. This leads to anaerobic conditions, commonly with accumulation of abnoxious decay and animal death. The process in which nutrient enriched water bodies support a dense plant population, which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.
What is biochemical oxygen demand (BOD)?
The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand (BOD). It is a measure of dissolved oxygen that would be needed by microorganisms to oxidise these compounds. The BOD is taken as a realistic measure of water quality ‘clear water’ would have a BOD value less than 5 ppm whereas highly polluted river would have a BOD value of 17 ppm or more.
What should be the concentration of fluoride in drinking water as per the international standard?
1 ppm or 1 mg dm-3
What is the cause of deficiency of fluoride in drinking water?
Difficiency of fluoride causes tooth decay.
What is the use of fluoride ion in drinking water?
The F– ions make the enamel on teeth much harder by converting hydroxy apatite into harder fluorapatite.
What is the effect of excess fluoride ion concentration in drinking water?
F– ion concentration above 2 ppm causes brown mottling of teeth. The concentration above 10 ppm causes harmful effect to bones and teeth.
What should be the upper limit concentration of lead in drinking water?
50 ppb (parts per billion)
What is the effect of excess lead (> 50 ppb) in drinking water?
Excess lead causes damage of kidney, liver, reproductive system etc.
What is the effect of sulphate (> 500 ppm) in drinking water?
Excess of sulphate causes laxative effect.
What is the maximum limit of nitrate in drinking water?
What is the effect of excess nitrate in drinking water?
Excess of nitrate in drinking water can cause disease called methemoglobinemia (blue baby syndrome).
Give the maximum prescribed concentration of Fe, Mn, Al, Cu, Zn and Cd in drinking water.
|Sl.No.||Metal||Maximum concentration (ppm or management dm-3|
What are pesticides? Give examples.
Pesticides are basically synthetic toxic chemicals with ecological repercussions. Examples: DDT, Aldrin, Dieldrin etc.
What are the effects of pesticides?
Most of the pesticides (organic toxins) are water insoluble and non biodegradable. Hence these toxins are transferred from lower trophic 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.
What are herbicides? Give examples.
These are compounds used to control weeds.
Examples: Sodium chlorate (NaClO3) and sodium arsinite (Na3AsO3)
What are the effects of herbicides?
Most herbicides are toxic to mammals and cause birth defects.
What are the main sources of biodegradable and non biodegradable industrial wastes?
Biodegradable industrial wastes generated by cotton mills, food processing units, paper mills and textile factories. Non biodegradable industrial wastes are generated by thermal power plants (fly ash), integrated iron and steel melting slag, metal industries like Al, Cu, Zn which produce mud and tailings.
Stratagies to Control Environmental Pollution
Mention the methods (strategies) to reduce the environmental pollution.
Important methods to control the environmental pollution are
- Burning and incineration
- Sewage treatment
- Digesting etc
What is green chemistry? What are the importance of green chemistry?
Green chemistry is a production process that would bring about minimum pollution or deterioration to the environment.
Green chemistry is a lost effective approach which involves reduction in materials, energy consumption and waste generation.
Green chemistry as an alternate tool for reducing pollution in day to day life. Explain with examples.
- In dry cleaning the use of chloroethene (carcinogen) is replaced by liquefied carbon dioxide with a suitable detergent (less harm to ground water) or by H2O2
- The use of chlorine gas for bleaching paper is replaced by H2O2 with suitable catalyst.
- Now a days ethanal is prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with the yield of 90%.