Plus One Chemistry Notes Chapter 14 Environmental Chemistry is part of Plus One Chemistry Notes. Here we have given Kerala Plus One Chemistry Notes Chapter 14 Environmental Chemistry.
|Text Book||NCERT Based|
|Chapter Name||Environmental Chemistry|
|Category||Plus One Kerala|
Kerala Plus One Chemistry Notes Chapter 14 Environmental Chemistry
Environmental Chemistry deals with the study of the origin, transport, reaction, effects and rates of chemical species in the environment.
The contamination of the environment with harmful substances due to certain natural phenomena and human activities is called environmental pollution.
Any substance that causes pollution is called a pollutant. A substance becomes pollutant when its concentration increases beyond a certain permissible limit in the environment.
Depending upon the regions of the atmosphere which gets polluted, the atmospheric pollution may be classified as:
1. Tropospheric Pollution.
Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air:
Tropospheric pollutants are of 2 types:
i. Gaseous air pollutants.
Oxides of sulphur, oxides of nitrogen, SO2 unburnt hydrocarbons, H2S, ozone and other oxidants.
a. Oxides of sulphur: SO2, SO3
- At low concentration SO2 causes respiratory diseases like asthma, bronchitis, etc.
- SO2 causes irritation to the eyes resulting in;tears and redness.
- SO2 on oxidation to SO3 give rise to photo chemical smog.
- Both SO2 and SO3 contribute to the acid rain.
b. Oxides of nitrogen: NO, NO2
NO does not have much adverse effect on human health.
NO2 is extremely toxic to living tissues and it damages plants, textiles fibres and metals. The most harmful effect of the oxides of the nitrogen is the production of photochemical smog. The oxides of nitrogen also contribute towards the acid rain.
c. Oxides of carbon: CO, CO2
CO is poisonous. CO has 200 times more affinity for haemoglobin than oxygen.
Hb + CO → CO.Hb (carboxy haemoglobin)
The oxygen carrying capacity of haemoglobin decreases and the blood becomes oxygen deficient. This leads to suffocation and even death depending upon the concentration of CO in the blood.
- CO2 causes mild narcotic effect, it stimulate the respiratory system and leads to asphyxiation.
- The increased concentration of CO2 causes a rise in atmospheric temperature. It leads to global warming.
Global Warming and Green house effect
The CO2 gas is absorbed by the earth and some of it is re-emitted to the earth’s atmosphere. As a result earth’s atmosphere is heated by the phenomena known as Green house effect.
List gases which are responsible for greenhouse effect
Carbon dioxide, methane, ozone, chloro fluorocarbons and water vapours in atmosphere are responsible for greenhouse effect Acid rain (A% ag). Acid rain is caused by of acid oxides such as oxides of sulphur and nitrogen in the air.
Damaging effect of Acid rain.
- Acid rain promotes corrosion.
- Acid rain damages buildings, iron bridges, statues, marble, cements, historical monuments such as Taj Mahal etc.
- Acid rain leads to the loss of soil fertility.
- Acid rain is harmful for plants as it dissolves and washes away nutrients needed for their growth.
Which acid is not present in acid rain?
HNO3, H2SO3 ,H2SO4, CH3COOH, H2O3
CH3COOH (Acetic acid) is not present in acid rain.
i. Taj Mahal and the Acid rain
Acid rain react with the marble of the Taj Mahal to form calcium sulphate and calcium nitrate, The salts CaSO4 and Ca(NO3)2 dissolve in water. As a result, marble of the Taj Mahal get corroded and lose its lustre due to its reaction with the acidic gases present in the atmosphere or with the acid rain.
ii. Particulateair pollutants.
Dust, mist, fumes, smoke, smog, metal particulates. The very small particles of solids and liquids suspended in the air are called particulates.
- Viable Particulates
The minute living organism that are dispersed in the air are called viable particulates,
eg., fungi, moulds etc.
- Non-viable Particulates
The small particles of non living materials are called non-viable particulates. Four types of non-viable particulates are:
a. Mist. The dispersion of liquid particles having diameter greater than one micrometer in the air is called mist. Mist is formed due to the condensation of vapour or atomisation of liquids.
b. Dust. Small solid particles which are temporarily suspended in the air are called dust.Dust particles are produced during crushing and grinding of solid materials.
c. Smoke. Smoke is a solid in air type of aerosol.
eg., tob+acco smoke, oil smoke.
What is the cause of acid rain ?
When rain falls through polluted air, it comes across chemicals such as gaseous oxides of sulphur, oxides of nitrogen, mists of hydrochloric acid and phosphoric acid etc. pH lowers down from 5.6 to 3.5. Sometimes, it becomes as low as 2.
Very small particles of solids and liquids dispersed in air are called aerosols. Aerosol particles have diameter less than one micrometer.
Fog is a liquid in air type aerosol. Fog is produced due to the condensation of water vapour present in the atmosphere,
d. Fumes. Fumes are generally obtained by the condensation of vapours during sublimation, distillation, boiling and other chemical reactions.
Very fine particles of ash produced during the burning of coal is called flyash. It contain partially burnt carbon particles.
Smog is a combination of smoke and fog suspended in air. There are two types of smog:
- Classical smog. It occurs in cool humid climate. It is a mixture of smoke, fog and sulphur dioxide. Chemically it is a reducing mixture and so it is called as reducing smog.
- Photochemical smog. It occurs in warm, dry and sunny climate. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. It has high concentration of oxidising agents and is there
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