CHEMISTRY 0620
SARA SAYEDA
1
CHEMISTRY 0620
SARA SAYEDA
2
CHEMISTRY 0620
SARA SAYEDA
3
CHEMISTRY 0620
SARA SAYEDA
4
CHEMISTRY 0620
Clean dry air:
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Containing no water vapour and only gases that are always present in the air.
It contains 78% N2, 21% O2, 0.9%Ar, 0.04% CO2 and 0.06 % other noble gases (helium, neon,
krypton, and xenon)
Separation of O2 and N2 from air:
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Process known as fractional distillation of liquefied air.
Air is first filtered to remove dust by passing it through an electrostatic dust precipitator.
Carbon Dioxide is removed by bubbling through Sodium Hydroxide
CO2 + NaOH → Na2CO3 + H2O
Water vapors are removed from the air in a drying tower.
Air is then compressed at about 200 atmospheric pressure and cools up to -200OC to make gas air
into liquid.
fractional distillation of liquid air
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Liquid air is passed into bottom of fractionating tower where it will be heated.
Column warmers at bottom than the top
Since nitrogen is more volatile (lower boiling point, liquifies at-196oC) than oxygen so it rises at the
top and pipped off.
While oxygen collects at the bottom (liquifies at -185oC)
So fractional distillation gives gaseous nitrogen and liquid oxygen.
Nitrogen obtained in this way contains about 1% of impurities, which are mainly argon and a little
oxygen.
This is also known as industrial preparation of nitrogen, oxygen and noble gas.
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CHEMISTRY 0620
Oxygen:
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Essential for respiration
Used Oxygen tanks in hospitals to treat people with respiratory problems.
Used in welding metals.
as an oxygen cylinder for deep-sea divers.
Used in making steel to remove carbon in pig iron.
Nitrogen
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Present in the atmosphere
Some bacteria use it directly from air to produce amino acids.
Used for food packaging.
Some combines with hydrogen to produce ammonia (raw material for fertilizer)
Pollution
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The presence of any substance that have a harmful effect on environment is known as pollution.
These harmful substances are known as pollutants.
Pollutants
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Substance, often harmful which is added to another substance.
Types of pollutions
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Water pollution
Air pollution
Soil pollution
Noise pollution etc
Air pollution
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Air pollution is the contamination of air due to the presence of substances in the atmosphere that
are harmful to the health of humans and other living beings, or cause damage to the climate or to
materials.
Air pollutants
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The common pollutants in the air are carbon monoxide, sulfur dioxide, oxides of nitrogen and lead
compounds.
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CHEMISTRY 0620
Air pollutants
Carbon monoxide
Sources
Incomplete combustion of
hydrocarbons in engines
Harmful effect
It reacts with the
hemoglobin in blood,
and prevents it from
carrying oxygen: leads
to headache, brain
damage,fatigue or
even death
Carbon dioxide
Complete combustion of
carbon containing fuels
increased global
warming leads to
climate change
Particulates (C soot)
Incomplete combustion of
hydrocarbons in engines
causes respiratory
(breathing) problems,
cancer
Oxides of Nitrogen
(NO and NO2)
Nitrogen and oxygen in the
air react together inside hot
car engine and
Lightning activity
Produces
photochemical smog
which irritates lungs,
Causes acid rain
Catalytic converters in
car exhausts.
Sulfur dioxide
Volcanoes and Combustion
of fossil fuel which contain
sulfur compounds.
Causes acid rain,
causes respiratory
(breathing) problems.
Removing sulfur
containing compounds
before combustion
(Using Calcium
Carbonate, calcium
oxide in flue gas
desulfurization)
Methane
Decomposition of
vegetation and waste gases
from digestion in animals,
swamp
increased global
warming leads to
climate change
Exhaust fumes from cars
High levels cause brain
damage in children,
lver and kindney
damage
Lead Compounds
Prevention
Regularly check heating
system, Catalytic
converters in car
exhausts.
Reduce reliance on
fossil fuel for
transportation and
electricity generation,
switch petrol car into
electric car, planting
more trees
Use fine mesh filters in
diesel vehicles
Change diet of cattles
Collect the gas and use
it as a energy sources,
reduce intake of
excessive meat rich diet
Using unleaded fuels
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CHEMISTRY 0620
Combustion of hydrocarbon
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Hydrocarbon from fractional distillation of crude oil are important fuels.
Reaction of fuel with oxygen is called combustion.
Types of combustion:
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Depending on the amount of oxygen available there are two types of combustion.
● Complete combustion
● Incomplete combustion
Complete combustion:
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When hydrocarbon fuel burns in plentiful supply of oxygen, carbon dioxide and water are
produced. This is called complete combustion of hydrocarbon.
The maximum amount of energy is given out.
In general reaction:
hydrocarbon + oxygen → carbon dioxide + water
In complete combustion:
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If hydrocarbon fuel burns in limited supply of oxygen, particles of soot (carbons) and Carbon
monoxide are produced. This is called incomplete combustion of hydrocarbon.
less amount of energy is released than complete combustion.
Catalytic converters
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Exhaust gases from car contain unburned hydrocarbons and carbon monoxide.
To convert the pollutant gases into harmless gases cars are fitted with catalytic converters.
It contains a transition metal as a catalyst (e.g: platinum, palladium, and rhodium) which convert
the pollutant gases into harmless gases. • Carbon monoxide is oxidized to carbon dioxide.
Unburned hydrocarbons are oxidized to carbon dioxide and water.
Reaction
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The following reaction takes place in the catalytic converter.
2CO + 2NO → 2CO2 + N2
2CO+ O2 → 2CO2
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CHEMISTRY 0620
Flue Gas Desulfurization
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This process takes place in flue gas exhausts in factories and power plants to remove Sulfur dioxide
from the flue gases.
The process a mixture of powdered limestone or slaked lime and water is sprayed on waste gases
or gases are passed through it to produce harmless substances.
Reaction:
CaCO3 + SO2 + O2 → CaSO4 + CO2
Ca (OH)2 + SO2 → CaSO3
CaSO3 + H2O+ O2 → CaSO4.2H2O (hydrated calcium sulfate/ gypsum)
Green House gases
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Gases that absorb infrared radiation from sun, so it remains trapped in earth’s atmosphere.
There are several greenhouse gases including water vapour, carbon dioxide, methane, nitrous oxide,
sulfur hexafluoride and chlorofluorocarbons (CFCs)
Two main greenhouse gases are methane and carbon dioxide.
Increase in these gases increases the greenhouse effect which causes increases increase in
temperature of atmosphere.
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CHEMISTRY 0620
Increase in the level of 2 main gases.
Greenhouse gas
Carbon dioxide, CO2
Methane, CH4
Human activities that increase its level
Combustion of fossil fuels and other carbon-based
fuels, in power stations, factories, car engines, and
homes.
Respiration
Decomposition of food under anerobic condition
Livestock farming; cattle and sheep release
methane from their digestive systems.
Greenhouse effect
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It’s a natural process in which the thermal energy from sun is trapped in earth atmosphere by
greenhouse gases.
CH4 and CO2 play important role in maintaining a constant temperature.
Average temperature for life is 15oC.
Without green house gases temperature would be -18oC (life wouldn’t exist)
How it happens?
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Some radiation from Sun reaches the Earth's surface.
Some thermal energy is absorbed but some radiations are reflected.
Greenhouse gases absorb that infrared radiation and increase the temperature of atmosphere and
reduces the heat loss to space.
Increase in level of greenhouse gases will rise the average temperature of atmosphere that leads to
global warming.
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CHEMISTRY 0620
Global Warming
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It occurs when green house gases absorb radiation and increase atmosphere temperature.
Effects:
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Melting of polar icecaps
Rising sea levels
Floods in low lying areas
Increase in temperature of earth decrease the amount of water and will cause drought.
dry soil and low rainfall effects food crops
To reduce the effect of climate change:
• Planting trees
• Reduction in livestock farming
• Less use of fossil fuels
• Increased use of hydrogen and renewable energy (e.g., wind, solar)
Photosynthesis
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Carbon dioxide is removed from the atmosphere by photosynthesis.
Photosynthesis is the reaction between carbon dioxide and water to produce glucose and oxygen
in the presence of chlorophyll and using energy from light.
Word Equation:
Carbon Dioxide + Water → Glucose + Oxygen
Balanced Chemical Equation:
6CO2 + 6H2O → C6H12O6 + 6O2
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CHEMISTRY 0620
Water
Tests for Water
Test
Anhydrous cobalt (II)chloride
Anhydrous copper (II)sulfate
Test melting and boiling point
Type of test
Chemical
Chemical
Physical
Result
Turns from blue to pink
Turns from white to blue
Sharp M.p (0oC) and B.p (100oC)
Reactions:
CuSO4 +5H2O → CaSO4.5H2O
CoCl2 +6H2O → CoCl2.6H2O
Note:
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Tap water is a mixture of natural minerals so it may interfere with experiments so distilled
water is used in practical chemistry rather than tap water.
Substance in natural water
Beneficial
Harmful
Dissolved oxygen
some metallic compound
Metallic compound
sewage
Nitrates and phosphates
Plastics
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CHEMISTRY 0620
Beneficial substances
1. Dissolved Oxygen (this is important for aquatic life)
• Solubility of Oxygen in water depends on temperature.
• Oxygen is removed from water by respiration.
2. Metal Compounds (Provide essential minerals for life)
• Water passing over rocks will dissolve some minerals like
• GI Na, K
• GII Ca, Mg
• Transition Fe,Co,Ni,Cu,Zn,Cr
Importance:
• Ca bones and teeth
• Fe production of hemoglobin
Harmful substances
1) Some toxic metal Compounds.
• Sources: Mining, metal smelting, waste disposal such as lead and mercury
• Effect of lead causes kidney and liver damages
• Effect of mercury: damages nervous system
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CHEMISTRY 0620
2) Sewage
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Leak of sewage water due to natural disaster
harmful microbes enters in drinking water and cause diseases water borne diseases like
diarrhea, typhoid, dysentery, cholera etc
3) Nitrates and Phosphate:
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NPK fertilizers used for crops (water soluble)
After spreading fertilizers heavy rain can cause run off (instead of being absorbed by plant it
will be washed over the surface of soil and enter into streams, lakes or rivers)
• It will cause rapid growth of algae which will block sunlight and disrupt photosynthesis
process.
e.g: Na5P3O10 (Penta sodium triphosphate)
4) Plastics
• insoluble in water
• Non-biodegradable.
Problems:
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Consume by marine life.
Block the digestive track.
Treatment of Domestic Water Supply
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These pollutants make the water unusable, and they have to be removed. To remove these
pollutants domestic water is taken from lakes and reservoirs and will be treated by using the
following steps to make the water usable.
1. Screening:
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Water is pumped into a sedimentation tank and treated with settling agent which causes small
impurities to clump together and settle down.
In this step large insoluble solid impurities will be removed such as plastics bags rocks etc.
2. Filtration:
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The water then undergoes filtration and will be filtered through layers of sand and gravel
to remove suspended solid particles (insoluble impurities).
3. Activated charcoal:
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Water has some dissolved organic compounds and unwanted odour or taste.
The water is then passed over beds of activated charcoal to remove it.
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CHEMISTRY 0620
5) Chlorination:
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The water is then chlorinated by adding chlorine before distributing to the homes.
Chlorine kills bacteria and other harmful microbes which might be present.
Desalination of Water
• Seawater is concentrated with salt (saline) and is not safe to drink.
• To remove the salt from the water and make it usable, the process of desalination is used.
• In this water is heated and it evaporates, leaving the salt behind.
• It is then condensed in a condenser and collected for use.
Uses of Water
Home
Industry
Drinking, cooking, and washing
Water jet cutting and water blasting
In car radiators, for gardens and plants
As a solvent in refining ores
Generating hydroelectricity
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CHEMISTRY 0620
Fertilizers:
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Substances which are added to the soil and taken up by plants to increase crop yield and
to improve plant growth.
Substances present inside fertilizers are Ammonium Salts and Nitrates.
Factory produces two main types of products.
2 main products
Straight N fertilizers
Urea
NPK compounds
mixture of ammonium nitrate
Nitrogen fertilizers
ammonium phosphate
Ammonium sulphate
potassium chloride
Elements
Function
Sources
Nitrogen
Makes chlorophyll and protein.
present in cabbage, leafy
Promotes healthy leaves
vegetables
Phosphorus
Promotes healthy roots
carrots, root crops
Potassium -
Promotes growth and healthy
apple, tomatoes
fruits and flowers
Note:
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Reaction with any alkali substance (except ammonia) displaces ammonia from its compound, for
example:
Calcium hydroxide + Ammonium chloride → Calcium chloride + Ammonia + Water
Using ammonium salt will make soil slightly acidic so to overcome we neutralize it by adding CaCO3
(Nitrochalk)
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