Kerala Technical Board Polytechnic Colleges, Engineering Chemistry-II Second semester-Module 4

1. By MUHAMMED SALMAN FARISH TP
Email: tpmsalman@gmail.com

3. Fuel
 Any substance which on proper burning (combustion) in
air gives large amount of heat, that can be used
economically for domestic and industrial purposes.
 Based on their occurrence fuels classified to two
1. Natural or primary fuel :- obtained from nature, eg;
wood,charcol, coal petroleum
2. Artificial or secondary fuel :- manufactured artificially,
from natural fuels, eg; diesel, kerosene, coke, water gas

4. Classification of fuels
Solid
Natural:
Wood, peat,
dung
Artificial:
charcoal, coke,
coal products
Liquid
Primary: crude
petroleum
Secondary:
diesel,
kerosene, LPG
Gaseous
Natural: e.g.;
natural gas
Artificial:
water gas,
producer gas
Nuclear
fuels
Eg; uranium
235, thorium-
232,
polonium

5. Calorific value
 The quantity of heat (in calories) liberated by the complete
combustion of a unit mass of the fuel in air or oxygen,
with the subsequent cooling of products of combustion to
the initial temperature of the fuel.
Characteristics of a good fuel.
 Should have
 high calorific value
 Moderate ignition temperature
 Low moisture content, easy transportation, efficient burning
without smoke.
 Moderate velocity of combustion, low storage coast

6. Cracking
 It is the breaking
of less volatile
larger molecules of
hydrocarbons from
petroleum into
more volatile
lower molecules of
hydrocarbons. Eg;
cracking of
petroleum.

7. Thermal cracking
 Breaking of hydrocarbons like fuel oil under high pressure
and high temperature about 770 K into lower alkanes by
random cleavage of carbon – carbon bonds.
 Eg: CH3-(CH2)8-CH3 →CH3-(CH2)6-CH3+ CH2═CH2
Decane octane ethene
Catalytic cracking
 Breaking higher alkanes to lower hydrocarbons in the
presence of a catalyst at lower temperature. Eg;
production of gasoline from petrol by using silica and
alumina mixture as a catalyst.

8. Water gas
 Is a mixture of Carbon monoxide (CO) and Hydrogen
gases. Prepared from sewage, saw dust, scrap wood and
news paper.
 Preparation of water gas( coal gasification)
C (g)+ H2O(g) CO (g) + H2 (g)
Uses and properties
For the production of methanol and other hydrocarbons.
As fuel gas in industries
As a source of hydrogen
For the manufacturing of ammonia
1270 K

9. Producer gas
It is a mixture of CO and Nitrogen gas.
Prepared by passing controlled amount of air through a
bed of red hot coke or coal at 11000 C, in a special
refractor called gas producer.
Uses and properties
1. Used as cheap fuel in industry
2. Heat treatment of furnaces
3. Alternative to diesel as a fuel
4. As a fuel to produce hot air in industries

10. Regions of atmosphere
Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere

11. Pollution
 Pollution is defined as any undesirable change occur to
our surroundings and is harmful to plants, animals and
human beings.
 A substance, which causes pollution, is known as
pollutant.
 Pollutants can be solid, liquid or gaseous substances
present in greater concentration than in natural abundance
and are produced due to human activities or due to natural
happenings.

12. Types of pollutions
Air
pollution.
Oxides of S, N, C,
H2S and Ozone
Dust, mist, fumes,
smoke, smog etc.
Water
pollution
Pathogens,
agricultural run off
Organic
wastes,acid rain,
Soil
pollution
Pesticides
Herbicides

13. Ozone depletion
O2 + O O3 (ozone)
When CFCs are released to atmosphere,
CF2Cl2 (g) →Cl ● (g) + ● CF2Cl (g)
Cl● (g) + O3 (g) → ClO●(g) + O2(g)
ClO● (g) + O (g) → Cl●(g) + O2(g)
The chlorine radicals are continuously regenerated and
cause the breakdown of ozone.
sunlight

14. Effects of Ozone Layer Depletion
It leads to ageing of skin, cataract, sunburn, skin cancer,
killing of many phytoplankton, damage to fish
productivity etc.
It 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

15. Green house effect
When the concentration of carbon dioxide in the
atmosphere is above the normal level (0.03%), it
absorbs more infra-red radiation from the solar energy
and hence the temperature of the earth’s atmosphere
increases. This is known as Green house effect. It
results in global warming.
Green house gases:- CH4, CO2, CFC’s, O3,
nitrous oxide and water vapour.

16. Adverse effects of Global
warming
 Due to global warming, the average global
temperature will increase.
 This will lead to the melting of polar ice caps and
flooding of low lying areas all over the earth.
 Increase in the global temperature results in the
infectious diseases like dengue, malaria, yellow fever,
sleeping sickness etc…

17. Acid rain
 When the pH of the rain water drops below 5.6, it is
called acid rain. Oxides of nitrogen and sulphur (e.g.
SO2 and NO2) are mainly responsible for acid rain.
2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq)
4NO2 (g) + O2 (g)+ 2H2O (l) → 4HNO3 (aq)
In atmosphere, rain water react with CO2 and forms.
H2O (l) + CO2 (g) → H2CO3(aq)
H2CO3(aq) → 2H+(aq) + HCO3
–(aq)

18. Harmful effects of acid rain
 It is harmful for agriculture, trees and plants.
 It causes respiratory ailments and skin cancer in human
beings and animals.
 It affects plants and animal life in aquatic ecosystem.
 It corrodes water pipes resulting in the dissolution of
heavy metals into the drinking water.
 Acid rain damages buildings and other structures made of
stone or metal (e.g. The Taj Mahal

19. Smog (Smoke+ Fog)
Classical
Smog
Mixture of smoke, fog
and SO2
Occur in cool & humid
atmosphere
Reducing mixture also
called reducing smog
Photochemical
Smog
Mixture of smoke, fog,
nitrogen oxide and un burnt
hydrocarbon
Occur in dry & sunny climate
Oxidizing mixture also called
oxidizing smog

20. Photochemical Smog
When fossil fuels burnt,
N2 + O2 → 2 NO
2 NO → 2NO2
This NO2 dissociates into NO & O
NO2(g) NO(g) + O(g)
O(g) + O2(g) → O3(g)
Both NO2 and O3 are strong oxidising agents and reacts with
unburnt hydrocarbons to produce compounds like
formaldehyde, acrolein and peroxyacetyl nitrate (PAN).
Sun light

21. Control of photochemical smog
Use catalytic converters in automobiles, which prevent the
release of nitrogen oxide and hydrocarbons to the
atmosphere.
Certain plants like Pinus, can metabolise nitrogen oxide.
So their plantation helps to reduce these oxides.
Otherwise,
it leads to serious health problems like
headache, chest pain and cracking of rubber and extensive
damage to plant life.

22. Green chemistry
 Green chemistry (also called sustainable chemistry) is an
area of chemistry focused on the design of products and
processes that minimize the use and generation of
dangerous substances.
 Reduce larger steps in chemical reactions.
 Reaction products should be free from toxicity.
 Proceed reactions to get only one product without forming
unwanted products.
 Convert waste products to byproduct or to reusable form.

23. Green chemistry in present scenario
1. Dry Cleaning of Clothes: Liquefied carbon dioxide,
with a suitable detergent is used for dry cleaning clothes.
2. Bleaching of Paper: Hydrogen peroxide (H2O2) with
suitable catalyst is used for bleaching paper.
3. Synthesis of Chemicals: Ethanal (CH3CHO) is now
commercially prepared by one step oxidation of ethene
in the presence of ionic catalyst in aqueous medium.
CH2 ═ CH2 + O2 CH3CHO
Catalyst
Pd(II)/Cu(II) in water