Manisha Kanwar semester 3

1. SAMRAT PRITHVIRAJ CHAUHAN
GOVERNMENT COLLEGE, AJMER
2022-23
DEPARTMENT OF CHEMISTRY
“ACID RAIN”
SUBMITTED BY;-
MANISHA KANWAR
M.Sc (CHEMISTRY) SEM-3rd

2. CONTENT
 INTRODUCTION.
 FORMATION OF DIFFERENT ACID WHICH
INVOLVED IN ACID RAIN.
 PHOTOCHEMICAL SMOG.
 pH OF ACID RAIN
 SOURCES OF ACID RAIN.
 HARMFUL EFFECT OF NITROGEN
DIOXIDE,OXIDES OF SULPHUR,HYDROGEN
SULPHIDE GAS.
 HARMUL EFFECT OF ACID RAIN .
 CONTROL OF ACID RAIN.
 REFERENCE

3. INTRODUCTION
The term acid rain was first used by ROBERT A SMITH in 1872
. What we call acid rain is the pollution that forms in the
atmosphere when chemicals in wastes gases such as
sulphur dioxides, nitrogen dioxides,etc.combine with the
water in the air. This acidic mixture then falls as
rain,sleet,mist or snow or as solid flakes.
Large cities and towns with high industrial activity or with
huge vehicular traffic show an appreciable presence of
gases like nitrogen dioxide,sulphur dioxide,and carbon
dioxide in the atomsphere. These gases dissolve in
rainwater and come down on the earth in form of carbonic
acid,sulphuric acid and nitric acid. Acid rain may contain
one or more acids depending upon the gases present in the
air.

5. FORMATION OF DIFFERENT ACID
WHICH INVOLVED IN ACID RAIN
FORMATION OF NITRIC ACID RAIN - When the
combustion of petrol takes place in internal combustion
engines of automobiles, a temperature of around
2500ᵒ C is produced. At these temp. small amounts of
nitrogen and oxygen present in the air combine to form
nitric acid. Nitric acid react with more oxygen from air
to form nitrogen dioxide. This combines with moisture
and oxygen present in the air to form nitric acid.
N₂ + O₂ 2NO
2NO + O₂ 2NO₂
4NO₂ + 2H₂O + O₂ 4HNO₃

6. FORMATION OF SULPHURIC ACID RAIN – Fossil and other
fuels contain small amount of sulphur. On
combustion,sulphur in the fuel is converted into sulphur
dioxide and further oxidies to sulphur trioxide by
atmospheric oxygen . Sulphur trioxide then dissolves in
rainwater or water vapour to form sulphuric acids.
S + O₂ SO₂
2SO₂ + O₂ 2SO₃
SO₃ + H₂O H₂SO₄
FORMATION OF CARBONIC ACID RAIN – Atmospheric
carbon dioxide dissolves in rainwater or moisture in the
air to form carbonic acid.
C + O₂ CO₂
CO₂ + H₂O H₂CO₃

7. PHOTOCHEMICAL SMOG
Automobiles discharge large amount of
nitrogen dioxide gas and hydrocarbon
vapours. Sunlight breaks the nitrogen
dioxides into reactive chemicals like
ozone and nascent oxygen which then
react with hydrocarbons and nitrogen
dioxides to form PEROXYACETYL
NITRATE (PAN) . The PAN and fog then
settle on smoke particles resulting in
the formation of photochemical smog

8. pH OF ACID RAIN
pH is a measure of the Hᶧ ion concentration and
indicates whether a solution is acidic ,alkaline
or neutral. Measured on a scale of 1 to 14 , the
pH of neutral water is .
pH ‹ 7 pH =7 pH › 7
ACIDIC NEUTRAL ALKALINE
ACID RAIN has pH ‹ 5.6

9. SOURCES OF ACID RAIN
Acid rain is the precipitation that contains high levels of sulphuric acid
and nitric acid.
NATURAL SOURCES OF ACID RAIN
• Gases emitted from volcanoes and geysers
• Gases released due to forest fires.
MAN-MADE SOURCE OF ACID RAIN
• Sulphur present in fossil fuels forms oxides when burnt . Oxides of
sulphur dissolve in rain water to form sulphuric acid.
• The internal combustion engine in auto-mobiles produces oxides of
nitrogen. These dissolve in rain water to form nitric acid.
• The high temperature produced in furnaces of factories and powar
plants also release oxides of nitrogen and sulphur.

10. HARMFUL EFFECT OF NITROGEN
DIOXIDE
• It inhibits the function of cilia in bronchi. As a
result ,dust and soot particles enter deep into
the lungs and cause respiratory problems.
• Presence of nitrogen dioxide in the air causes
irritation in eyes.
• It causes acid rain containing nitric acid ,
which is harmful to plants, aquatic and
monuments.

11. HARMFUL EFFECTS OF OXIDES OF
SULPHUR
• Sulphur dioxide and sulphur trioxide gases
combine with fog to form smog in winter.
• Small concentration of sulphur dioxide and
sulphur trioxide gases causes headache and
nausea. High concentrations of these gases
can cause severe lung ailments and even
death
• Its forms acid rain containing sulphuric acid.

12. HARMFUL EFFECT OF HYDROGEN
SULPHIDE GAS
It is a poisonous gas characterised by the smell
of rotton eggs.
• Hydrogen sulphide takes up the iron from the
blood and forms iron sulphide.
• Small amount of gas causes nausea.
• Sore throat and irritation in eyes result when
the concentration of hydrogen sulphide is
more.

13. HARMFUL EFFECT OF ACID RAIN
1.Acid rain badly destroys
monuments and buildings ,
particularly those of white
marble. The taj mahal at
Agra is under threat as
fumes from the nearby
factories is slowly damaging
it. Calcium bicarbonate is
water souble, hence there is
continuous erosion of
marbles due to these
pollutants, known as
“STONE CANCER”

14. • Acid rain is responsible
for rusting and
corrosion of metals ,
particulary iron. Iron is
extensively used for
making gates ,
railing,fencing,etc.
• Water in the lakes and
rivers becomes acidic
due to acid rain. This
leads to the destruction
of aquatic plants and
animals.

15. • Acid rain dissolves basic nutrients like calcium
and magnesium carbonates in the soil to form
souble salts like calcium and magnesium
nitrates which are washed away. This disturbs
the pH of the soil and kills natural bacteria of
the soil.
• It causes chlorosis (discoloration of green
pigment) and necrosis ( death of tissues in
plants).

16. CONTROL OF ACID RAIN
1) Reduction in emission of acid rain gases such
as SOₓ (oxides of sulphur) and NOₓ (oxides of
nitrogen) from industries.
2) Use of srubbers , electrostatic precipitators ,
etc,in factories.
3) Use of lime to neutralise acidity of soils.
4) Formulation of strict laws to reduce emission.
5) Public awareness of the problem.

17. REFERENCE
• ENVIRONMENTAL CHEMISTRY – H. KAUR( A
PRAGATI EDITION).
• AIR POLLUTION AND CONTROL- RAJNI KANT AND
KESHAV KANT.
• https://www.javatpoint.com/acid-rain
• https://www.britannica.com/story/what-
happened-to-acid-rain
• https://mythgyaan.com/why-taj-mahal-turning-
yellow-green/