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Class notes chemistry Chemistry Simplified NCERT Class 11
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Class notes chemistry Chemistry Simplified NCERT Class 11
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UNIT 14 ENVIRONMENTAL CHEMISTRY1. Define Environmental Pollution.
Environmental pollution is the effect of undesirable changes in our surroundings
that have harmful effects in plants, animals and human beings.
2. What are pollutants? How are they produced?
A substance which causes pollution is known as pollutants.
Pollutants can be solid, liquid or gaseous substances present in greater
concentration and are produced due to human activities or due to natural
happenings.
3. What is a primary pollutant?
A primary pollutant is an air pollutant emitted directly from a source.
Primary pollutants are those which are present in the environment as such after
their formations.
Eg:- CO, NO, and SO2.
4. What is a secondary pollutant?
A secondary pollutant is not directly emitted as such, but forms when other primary
pollutants react in the atmosphere.
Eg:- Ozone, NO2, SO3, Peroxy Acyl Nitrates (PAN).
5. Briefly explain tropospheric pollution.
Troposphere extends up to a height of about 10 km from sea level.
Tropospheric pollution occurs due to the presence of undesirable solid or gaseous
particles in the air.
1. Gaseous Pollutants
These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide,
hydrocarbons, ozone and other oxidants.
They cause asthma, bronchitis and can lead to acute respiratory diseases.
2. Particulate Pollutants
These are dust, moist fumes, smoke, smog etc.
These are present in vehicle emissions, smoke particles from fires, dust particles
and ash from industries.
These are dust, moist fumes, smoke, smog etc.
6. What are viable pollutants?
The viable particulates are minute living organisms that are dispersed in the
atmosphere.
E.g., Bacteria, Fungi, Moulds, Algae etc.
7. What are non-viable pollutants?
Non-viable particulates may be classified according to their nature and size as follows.
PREPARED BY HAIZEL G. ROY, HSST (HG) CHEMISTRY, GOVT. H.S.S. KALAMASSERY ERNAKULAM Page | 1
, (a) Smoke particulates consist of solid or mixture of solid and liquid particles
formed during combustion of organic matter.
E.g. Cigarette smoke, smoke from burning of fossil fuel, garbage and dry leaves, oil
smoke etc.
(b) Dust is composed of fine solid particles produced during crushing, grinding and
attribution of solid materials.
E.g. Sand from sand blasting, saw dust from wood works, pulverized coal, cement
and fly ash from factories, dust storms etc.
(c) Mists are produced by particles of spray liquids and by condensation of vapours
in air.
E.g. Sulphuric Acid mist, Herbicides, Insecticides etc.
(d) Fumes are obtained by the condensation of vapours during sublimation,
distillation, boiling and several other chemical reactions.
E.g. Organic solvents, metals and metallic oxides form fume particles.
8. What are the harmful effects of Nitrogen and its compounds?
The irritant red haze in the traffic and congested places is due to oxides of nitrogen.
Higher concentrations of NO2 damage the leaves of plants and retard the rate of
photosynthesis.
Nitrogen dioxide is a lung irritant that can lead to an acute respiratory disease in
children.
It is toxic to living tissues also.
Nitrogen dioxide is also harmful to various textile fibres and metals.
9. Carbon monoxide gas is more dangerous than carbon dioxide. Why?
Carbon monoxide when inhaled reacts with haemoglobin to form the complex
carboxy haemoglobin.
Therefore, haemoglobin cannot carry oxygen to the various parts of the body.
On the other hand, the presence of carbon dioxide can lead only to green house
effect causing global warming.
10. What is acid rain?
Normally rain water has a pH of 5.6.
It is due to the presence of H+ ions formed by the reaction of rain water with CO2
present in the atmosphere.
H2O + CO2 H2CO3
H2CO3 H+ + HCO3─
When the pH of the rain water drops below 5.6, it is called acid rain.
The oxides of nitrogen (NO2) and sulphur (SO2) present in the atmosphere after
oxidation and reaction with water forms sulphuric acid and nitric acid.
These acids contribute to acid rain.
PREPARED BY HAIZEL G. ROY, HSST (HG) CHEMISTRY, GOVT. H.S.S. KALAMASSERY ERNAKULAM Page | 2
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