Environmental Chemistry Class 11 Notes Chemistry Chapter 14

 Page 1


? Environmental chemistry deals with the study of the origin, transport,
reactions, effects, fates of chemical species in the environment.
? Environmental pollution is the effect of undesirable changes in our
surroundings that have harmful effects on plants, animals and human be ings.
? Main regions of atmosphere are (i) trophosphere (ii) Stratosphere
(iii) mesosphere and (iv) ionosphere.
? Pollutants can be (i) gaseous air pollutants (e.g., SO
2
, NO
2
, CO
2
, H
2
S,
O
3
 hydrocarbons etc. and (ii) particular pollutants ( e.g., dust, mist, fumes,
smoke, smog etc.)
? Gaseous air pollutants : SO
2
 can cause acute irritation to the membranes
of the eyes resulting in tears and redness. It is also responsible for acid rain.
NO
2
 is extremely toxic to living tissues, textiles and in the production of
photochemical smog.
? Particulate pollutants : They are of two types :
 (i) Visible particulate or viable particulates : There are the minute living
organisms that are disposed in atmosphere. Ex. Bacteria, fungi, moulds etc.
 (ii) Non-viable particulates : These are formed either by the breakdown
of larger materials or by the condensation of minute particles and droplets.
For example mists, smoke, fumes and dust.
? Green House Effect is the phenomenon of warming of earth by absorption
and re-emission of solar radiations.
? Green house gases are CO
2
, CH
4
, O
3
 water vapours, chlorofluoro carbons
etc.
Page 2


? Environmental chemistry deals with the study of the origin, transport,
reactions, effects, fates of chemical species in the environment.
? Environmental pollution is the effect of undesirable changes in our
surroundings that have harmful effects on plants, animals and human be ings.
? Main regions of atmosphere are (i) trophosphere (ii) Stratosphere
(iii) mesosphere and (iv) ionosphere.
? Pollutants can be (i) gaseous air pollutants (e.g., SO
2
, NO
2
, CO
2
, H
2
S,
O
3
 hydrocarbons etc. and (ii) particular pollutants ( e.g., dust, mist, fumes,
smoke, smog etc.)
? Gaseous air pollutants : SO
2
 can cause acute irritation to the membranes
of the eyes resulting in tears and redness. It is also responsible for acid rain.
NO
2
 is extremely toxic to living tissues, textiles and in the production of
photochemical smog.
? Particulate pollutants : They are of two types :
 (i) Visible particulate or viable particulates : There are the minute living
organisms that are disposed in atmosphere. Ex. Bacteria, fungi, moulds etc.
 (ii) Non-viable particulates : These are formed either by the breakdown
of larger materials or by the condensation of minute particles and droplets.
For example mists, smoke, fumes and dust.
? Green House Effect is the phenomenon of warming of earth by absorption
and re-emission of solar radiations.
? Green house gases are CO
2
, CH
4
, O
3
 water vapours, chlorofluoro carbons
etc.
? Acid raid : When the pH of the rain water drops below 5.6, it is called acid
rain. It damages monuments and structures made of firm marble, corrode
articles made from metals, destroy plants and trees and it is also harmful
to the aquatic life in lakes and rivers.
 H
2
O + SO
2
 ?? H
2
SO
3
SO
2
 + O
3
 ?? SO
3 
+ O
2
SO
3
 + H
2
O ?? H
2
SO
4
NO + O
2
 ?? NO
2
NO
2
 + H
2
O ?? HNO
3
 + HNO
2
? Ozone hole is formed over South Pole due to depletion of ozone layer.
CFCs and NO are responsible for ozone layer deplection.
? Effects of deplection of ozone layer : With the depletion of ozone layer,
more UV radiation filters into troposphere. UV radiations lead to ageing
of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons,
damage to fish productivity etc.
? Smog is derived from smoke and fog.
? Classical smog occurs in cool humid climate. It is a mixture of smoke, fog
and sulphur dioxide. It is also called reducing smog.
? Photochemical smog occurs in warm and dry sunny climate. It has high
concentration of oxidizing agents and therefore, it is also called as oxidizing
smog.
? There are three main components of photochemical smog : nitrogen oxides,
ozone and organic derivatives such as acrolein, formaldehyde, peroxyacetyl
nitrate (PAN). PAN has the highest toxicity to plants attacking younger
leaves and causing ‘bronzing’ and ‘glazing’ of their surface.
? Water Pollution : It is mainly caused by industrial waste which include
heavy metals like Cd, Pb and Hg.
? Eutrophication : The process is which nutrient enriched water bodies
support a dense plant population, which kills animal life by depriving
Page 3


? Environmental chemistry deals with the study of the origin, transport,
reactions, effects, fates of chemical species in the environment.
? Environmental pollution is the effect of undesirable changes in our
surroundings that have harmful effects on plants, animals and human be ings.
? Main regions of atmosphere are (i) trophosphere (ii) Stratosphere
(iii) mesosphere and (iv) ionosphere.
? Pollutants can be (i) gaseous air pollutants (e.g., SO
2
, NO
2
, CO
2
, H
2
S,
O
3
 hydrocarbons etc. and (ii) particular pollutants ( e.g., dust, mist, fumes,
smoke, smog etc.)
? Gaseous air pollutants : SO
2
 can cause acute irritation to the membranes
of the eyes resulting in tears and redness. It is also responsible for acid rain.
NO
2
 is extremely toxic to living tissues, textiles and in the production of
photochemical smog.
? Particulate pollutants : They are of two types :
 (i) Visible particulate or viable particulates : There are the minute living
organisms that are disposed in atmosphere. Ex. Bacteria, fungi, moulds etc.
 (ii) Non-viable particulates : These are formed either by the breakdown
of larger materials or by the condensation of minute particles and droplets.
For example mists, smoke, fumes and dust.
? Green House Effect is the phenomenon of warming of earth by absorption
and re-emission of solar radiations.
? Green house gases are CO
2
, CH
4
, O
3
 water vapours, chlorofluoro carbons
etc.
? Acid raid : When the pH of the rain water drops below 5.6, it is called acid
rain. It damages monuments and structures made of firm marble, corrode
articles made from metals, destroy plants and trees and it is also harmful
to the aquatic life in lakes and rivers.
 H
2
O + SO
2
 ?? H
2
SO
3
SO
2
 + O
3
 ?? SO
3 
+ O
2
SO
3
 + H
2
O ?? H
2
SO
4
NO + O
2
 ?? NO
2
NO
2
 + H
2
O ?? HNO
3
 + HNO
2
? Ozone hole is formed over South Pole due to depletion of ozone layer.
CFCs and NO are responsible for ozone layer deplection.
? Effects of deplection of ozone layer : With the depletion of ozone layer,
more UV radiation filters into troposphere. UV radiations lead to ageing
of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons,
damage to fish productivity etc.
? Smog is derived from smoke and fog.
? Classical smog occurs in cool humid climate. It is a mixture of smoke, fog
and sulphur dioxide. It is also called reducing smog.
? Photochemical smog occurs in warm and dry sunny climate. It has high
concentration of oxidizing agents and therefore, it is also called as oxidizing
smog.
? There are three main components of photochemical smog : nitrogen oxides,
ozone and organic derivatives such as acrolein, formaldehyde, peroxyacetyl
nitrate (PAN). PAN has the highest toxicity to plants attacking younger
leaves and causing ‘bronzing’ and ‘glazing’ of their surface.
? Water Pollution : It is mainly caused by industrial waste which include
heavy metals like Cd, Pb and Hg.
? Eutrophication : The process is which nutrient enriched water bodies
support a dense plant population, which kills animal life by depriving
it of oxygen and result in subsequent loss of biodiversity is known as 
Eutrophication.
? 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).
? Land Pollution : It is caused by pesticides. Most pesticides can be divided
into three categories—Insecticides, Herbicides and fungicides.
? The environmental pollution can be controlled :
(a) By recycling of household and industrial wastes.
(b) By sewage treatment.
(c) Incineration converts organic material to CO
2
 and H
2
O.
? Green Chemistry is a way of thinking and is about utilizing the existing
knowledge and principles of chemistry and other science to reduce the
adverse impact on environment.
? Green Chemistry in Day to Day life :
(1) Dry cleaning of clothes by using liquified CO
2
 along with detergent
instead of tetrachloroethene.
(2) Bleaching of paper and clothes by using H
2
O
2
 a better bleaching agent
as compared to Cl
2
.
? Global Warming:
About 75% of the solar energy reaching the earth is absorbed by the earth's
surface, which increases its temprature, the rest of the heat radiates back
to the atmosphere. Some of the heat is trapped by the gases such as CO
2
,
CH
4
, O
3
, CFCS and H
2
O vapour they add to the heating of the atmosphere
causing Global worming.