Topic 3 – Chemical
Monitoring and
Management
By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
11 – THE INDUSTRIAL CHEMIST
11.1 – THE WORK OF AN INDUSTRIAL CHEMIST
THE ROLE OF A WORKING CHEMIST




Chemists employed in the industrial sector have many roles including:
o Development Chemist - Designing chemical processes for the manufacture of a chemical product
to ensure the rate of the reaction and yield product are optimised.
o Production Chemist - Working with chemical engineers to designing the equipment to carry out
the industrial process
o Research Chemist - Undertaking ongoing research to improve the product or process or to
develop new products.
Teamwork, collaboration and communication skills are important for chemists.
A company has many chemists that are skilled in different areas.
There are a variety of chemists, including:
o Environmental chemist:
 Employed by a wide variety of organisations, including mining.
 Developed expertise in analytical chemistry.
 They collect, analyse and assess environmental data from the air, water and soil.
o Metallurgical chemist:
 They have a high understanding of metals, alloys and ores and their reactions.
 They specialise in all aspects of the use and development of metals and alloys in society.
 They design and monitor methods of extracting metals from ores.
o Biochemists:
 They help determine the chemical structure and functions of molecules in living things.
 They study organic chemistry and biochemistry
 They can be employed in areas including pharmaceutical laboratories, hospitals and in the
food and agricultural industries.
MONITORING COMBUSTION REACTIONS



The combustion of alkanes obtained from petroleum is a major source of heat and power.
Though they are stable in oxygen, they are combustible when ignited - the products from this are carbon
dioxide and water.
In a space where is a plentiful supply of oxygen the reaction is:
2𝐶8 𝐻18(𝑔) + 25𝑂2(𝑔) → 16𝐶𝑂2(𝑔) + 18𝐻2 𝑂(𝑙)

However when there is a lack of oxygen - like in a car engine - then incomplete combustion may occur:
2𝐶8 𝐻18(𝑔) + 20𝑂2(𝑔) → 8𝐶𝑂2(𝑔) + 6𝐶𝑂(𝑔) + 2𝐶(𝑠) + 18𝐻2 𝑂(𝑙)
CATALYTIC CONVERTERS AND EMISSION CONTROL


Industrial chemists have developed catalysts that help to reduce carbon monoxide, nitrogen oxide and
unburnt hydrocarbon emissions from vehicle exhausts.
Catalytic converters are made from alloys of rhodium and platinum - they speed up reactions that
convert pollutant gases to materials which are present in the air naturally.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management

The aim of this is to convert otherwise dangers NO and CO to N2 and CO2 respectively and also unburnt
hydrocarbons into water.
11.2 – THE HABER PROCESS
THE USES AND IMPORTANCE OF AMMONIA




Ammonia is a gas that produces an alkaline solution when dissolved in water.
Solutions of ammonia in water are used domestically are cleaning agents and also as refrigerant gas.
Ammonia is the feedstock for a large variety of industrial chemicals.
Fertilisers account for over 80% of worldwide use of ammonia.
Industrial Product Derived from Ammonia
 Urea
 Ammonium Sulfate
 Ammonium Nitrate
 Ammonium Hydrogen Phosphate
 Nitric Acid
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
Acrylonitrile
Diaminoalkanes
Cyanides
Hydrazine
Sulfonamides
Aniline Derivatives
Alkylammonium Hydrocarbons
Use of Product
 Fertilisers

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
Production of explosives
Nitrate salts
Strong laboratory acids
Acrylic plastics
Nylon plastics
Extraction of gold from gold veins
Rocket propellant
Antibiotic drugs
Dyes
Cationic detergents
INDUSTRIAL MANUFACTURE OF AMMONIA


The production involves balancing the conditions of the reaction so that the products are produced at a
fast rate and the quantity is of the product is maximised.
Ammonia is manufactured by a process developed by Fritz Haber in early 20th century.
o It was manufactured from its component gas elements - the reaction is exothermic.
𝑁2(𝑔) + 3𝐻2(𝑔) ⇌ 2𝑁𝐻3(𝑔) ∆ = −92𝑘𝐽/𝑚𝑜𝑙

At the standard conditions of temperature and pressure lies to the left - Haber process changes this.
o Conditions in the Haber process make the manufacturing of ammonia viable.
FEEDSTOCKS FOR THE HABER PROCESS


The ammonia industry requires nitrogen and hydrogen.
o They are derived from air, water and natural gas.
The ammonia produced is not only used to make solid fertiliser, but is also directly applied to the soil in
anhydrous gaseous form.
NITROGEN

Filtered air is the source of nitrogen for the Haber process.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management


Air contains ~78% nitrogen by volume.
o An expensive method for nitrogen extraction is to fractionally distil liquefied air.
Nitrogen is more commonly extracted from air using chemical reactions involving natural gas or
methane.
HYDROGEN

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
Hydrogen can be obtained via the
electrolysis of salt water - but it is too
expensive.
Hydrogen is derived from the steam
reforming of natural gas - CH4.
Extraction of hydrogen is as follows:
o Natural gas is purified to
remove sulfur compounds
through a cobalt/nickel/alumina
catalyst.
o Hydrogen is extracted by
reacting natural gas with steam at about 750°C with nickel catalyst - primary steam reforming 90% of methane is consumed.
o The introduction of air produces steam with nitrogen remaining unreacted - high temperatures
~1000°C ensures combustion of almost all methane.
o Carbon monoxide is removed by passing it over two different catalysts - iron oxide (~400°C) and
cooper (~200°C)
 CO must be removed as it is poisonous - 0.2% remaining
 Reaction is exothermic - heat is recovered for further use.
o CO2 is removed by neutralisation with potassium carbonate under pressure - the decomposed
potassium hydrogen carbonate is stored for further use.
There must not be any oxygen as it is explosive with hydrogen under high pressure and temperature.
The final gaseous mixture contains nitrogen and hydrogen in a ratio of 1:3 - very small amounts of
methane and argon are present.
HABER PROCESS

The Haber Process is as follows:
o Reactants pass through the
catalytic reactors
o The mixture is cooled to condense
out the ammonia formed
o The ammonia is drained out as
required with the unreacted gas fed
back into the catalyst chamber with
incoming reactants
o None of the reactant mixture is
wasted.
HABER PROCESS

The conditions present in the Haber process is a compromise between temperature and pressure and
also kinetic factors.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
𝑁2(𝑔) + 3𝐻2(𝑔) ⇌ 2𝑁𝐻3(𝑔) ∆ = −92𝑘𝐽/𝑚𝑜𝑙
EQUILIBRIUM FACTORS


Temperature:
o The Haber process is an
exothermic reaction - high
temperature, low yield.
o According to L.C.P. - Lower the
temperature the higher the yield.
Pressure:
o Stoichiometric equation shows
that there are 4 moles of
reactants for 2 moles of products increased pressure, high yield.
o According to L.C.P. - Higher the pressure, the higher the yield.
KINETIC FACTORS




Kinetic factors relate the speed at which reactions occur and how rapidly the ammonia is formed.
High temperatures increase kinetic energies of molecules therefore increased productivity.
High pressures increase frequency of collisions therefore increased productivity.
The presence of a catalyst increases the reaction rate.
ECONOMIC FACTORS




Constructing strong pipes and maintaining a high-pressure reactor vessel is very expensive - therefore
selected pressure should not be too high.
Ammonia plants should be located locally with natural gas.
Heat is not wasted as they are recycled in heat exchangers.
Carbon dioxide is not wasted as it is used to manufacture urea and sold to brewers and soft drink
manufacturers.
COMPROMISE CONDITIONS

The conditions in the manufacturing of ammonia vary but these are some of the typical ranges:
o Reactants: N2 and H2 (ratio 1:3) can be shifted to the left by increased concentration stoichiometric ratio must be maintained.
o Pressure: 15-35MPa - although it should be as high as possible, but economic and safety concerns
require the pressure to be lower.
o Temperature: 400°C-550°C - equilibrium and kinetic factors are a problem; a compromise has to
be struck so that the activation energy level can be reached.
o Catalyst: Magnetite (Fe3O4) - fused with K2O, Al2O3, and CaO - it is then reduced to porous iron. By
grinding the iron catalyst to produce maximum surface area - this allows low temperatures and
low pressures to be used.
MONITORING AND MANAGEMENT


The Haber process must be monitored and managed for productivity maximisation and safety concerns.
Reasons include:
o Feedstock must be pure and free contaminants - they interfere with yield and can damage the
catalyst.
 Oxygen must not be present as it is explosive.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
o
o


Ratio of nitrogen and hydrogen must be kept at 1:3 for optimum production.
Temperature and pressure should be maintained - temperature too high can damage the
catalyst, pressure too high may cause the vessels to rupture.
o Overtime, minor gases in the atmosphere such as argon and inert gases accumulate - they need
to be removed when it reaches 5%.
o Remove ammonia at regular intervals to ensure no impurity contamination
o Structural integrity of reaction vessel must be maintained.
Monitoring devices are connected to critical parts of the containment vessels.
Electronic devices sound alarms when values fall outside acceptable limits.
12 – THE ANALYTICAL CHEMIST
12.1 – IDENTIFICATION OF IONS
ANION ANALYSES
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Chemists analyse materials for the
presence of specific cations and
anions.
Anions can be identified and
distinguished using a variety of
simple qualitative tests involving
the formation of gasses or
precipitates.
There is a series of elimination
tests conducted in strict order.
Then there are additional
confirmation tests.
Solubility rules include:
o Nitrate salts are soluble no precipitation of cations
o Group 1 salts are soluble no precipitation
Anion
Soluble
𝟐−
𝑪𝑶𝟑
𝑁𝑎+ , 𝐾 + , 𝑁𝐻4+
−
Most
𝑪𝒍
−
+
+
𝑶𝑯
𝑁𝑎 , 𝐾 , 𝑁𝐻4+ , 𝐵𝑎2+
𝑷𝑶𝟑−
𝑁𝑎+ , 𝐾 + , 𝑁𝐻4+
𝟒
Most
𝑺𝑶𝟐−
𝟒
ANION ELIMINATION TESTS


Anion
𝑪𝑶𝟐−
𝟑
Slightly Soluble
𝑃𝑏 2+
𝐶𝑎2+
𝐶𝑎2+ , 𝐴𝑔+
Insoluble
Most
𝐴𝑔+
Most
Most
𝐵𝑎2+ , 𝑃𝑏 2+
To test for unknown solutions, there is a listed sequence.
It is known as the elimination sequence - must be done in order to prevent invalid conclusions.
Procedure
Add 2mol/L nitric acid
5
By: Raymond Chen
Observation/Conclusion
Effervescence of colourless gas (CO2)
indicates a carbonate
Use limewater to confirm
Topic 3 – Chemical Monitoring and Management
Confirmation Test: Test the original solution with pH
paper
𝑺𝑶𝟐−
𝟒
Acidify the unknown solution with nitric acid and add
drops of dilute barium nitrate
Confirmation Test: Add drops of lead nitrate solution
𝑪𝒍−
Acidify the unknown solution with nitric acid and add
silver nitrate solution
Confirmation Test: Add ammonia solution then heat in
water bath
𝑷𝑶𝟑−
𝟒
Add drops of ammonia solution then solution of barium
nitrate
Confirmation Tests:
Add ammonium molybdate and warm the mixture
Acidify the solution with sulfuric acid, then add
ammonium molybdate and ascorbic acid
𝐶𝑂32− + 2𝐻 + → 𝐶𝑂2(𝑔) + 𝐻2 𝑂(𝑙)
If solution is alkaline then the results are
true.
𝐶𝑂32− + 𝐻2 𝑂(𝑙) ⇌ 𝐻𝐶𝑂3− + 𝑂𝐻 −
A white precipitate of barium sulfate
indicates sulfate ions are present
𝑆𝑂42− + 𝐵𝑎2+ → 𝐵𝑎𝑆𝑂4(𝑠)
A white lead (II) sulfate precipitate forms
𝑆𝑂42− + 𝑃𝑏 2+ → 𝑃𝑏𝑆𝑂4(𝑠)
A white precipitate of silver chloride
𝐶𝑙 − + 𝐴𝑔+ → 𝐴𝑔𝐶𝑙(𝑠)
White precipitate should dissolved
−
𝐴𝑔𝐶𝑙(𝑠) + 2𝑁𝐻3 → 𝐴𝑔(𝑁𝐻3 )+
2 + 𝐶𝑙
White precipitates forms
2𝑃𝑂43− + 3𝐵𝑎2+ → 𝐵𝑎3 (𝑃𝑂4 )2(𝑠)
A yellow precipitate of ammonium
phosphomolybdate forms
A blue complex forms
CATION ANALYSIS
COLOUR OF SOLUTION

In aqueous solution many cations are colourless - but some are distinctive in colour
Hydrated Cation
𝑭𝒆𝟑+
𝑭𝒆𝟐+
𝑪𝒖𝟐+
Solution Colour
Yellow-orange to pale yellow
Pale green to colourless
Blue to green-blue
FLAME TESTS


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

Many metal ions produce characteristic colours when their salts are heated - flame test
Some metal ions produce
characteristic flame colours.
Chloride salts of various cations work
best.
As an atom is heated the electrons in
the atom moves to a higher energy
level but it is unstable hence they fall
back.
According to the Law of Conservation
of Energy the energy in the electron is
emitted in the form of a frequency in
the electromagnetic spectrum coloured photons.
There are two ways to perform the
flame test:
o Dip a platinum wire into
concentrated HCl to clean it.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management

o Heat the wire to remove impurities
o Dip the wire into acid and then into powdered salt so that the salt sticks
o Heat using Bunsen burner and colour is displayed in the flame
Dissolve the chloride salt in water and spray the resulting solution into the blue Bunsen flame using an
atomiser.
o Sodium may sometimes mask the colour of the unknown metal – it has a strong yellow colour.
Cation
Calcium
Barium
Copper
Sodium
Strontium
CATION ELIMINATION TESTS



Flame Colour
Brick red
Yellow-green
Green
Yellow
Scarlet-Red
Like with anions, a series of elimination tests are carried out.
These elimination tests are based on the formation of precipitates in solutions of varying pH.
The cation solutions should have a minimum concentration of 0.1 molar.
Cations
Pb2+
Procedure
Add hydrochloric acid
Confirmation Test: Add drops of sodium
iodide to original solution
Ba2+, Ca2+
Add sulfuric acid
Confirmation Test:
Add solution of sodium fluoride
Conduct flame test
Cu2+
Fe2+, Fe3+
Add sodium hydroxide then add
ammonia solution
Confirmation Test: Conduct flame test
Add same of sodium hydroxide
Confirmation Test: Add HCl
Add potassium hexacyanferrate
reagent
Add potassium thiocyanate reagent
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By: Raymond Chen
Observation/Conclusion
White precipitate indicates lead ions
𝑃𝑏 2+ + 2𝐶𝑙 − → 𝑃𝑏𝐶𝑙2(𝑠)
Lead chloride is soluble in hot water
Yellow precipitate forms
𝑃𝑏 2+ + 2𝐼 − → 𝑃𝑏𝐼2(𝑠)
White precipitate indicates either barium or calcium ions
𝐶𝑎2+ + 𝑆𝑂42− → 𝐶𝑎𝑆𝑂4(𝑠)
𝐵𝑎2+ + 𝑆𝑂42− → 𝐵𝑎𝑆𝑂4(𝑠)
White precipitate confirms calcium - no precipitate
confirms barium
Brick red - calcium
𝐶𝑎2+ + 2𝐹 − → 𝐶𝑎𝐹2(𝑠)
Yellow-green - barium
Blue precipitate forms from an original blue-green
solution - precipitate dissolves in ammonia to form deep
blue solution
𝐶𝑢2+ + 2𝑂𝐻 − → 𝐶𝑢(𝑂𝐻)2(𝑠)
−
𝐶𝑢(𝑂𝐻)2(𝑠) + 4𝑁𝐻3 → 𝐶𝑢(𝑁𝐻3 )2+
4 + 2𝑂𝐻
Green flame
Brown precipitate indicates Fe3+
𝐹𝑒 3+ + 3𝑂𝐻 − → 𝐹𝑒(𝑂𝐻)3(𝑠)
Greenish precipitate indicates Fe2+ - rapidly turns brown
𝐹𝑒 2+ + 2𝑂𝐻 − → 𝐹𝑒(𝑂𝐻)2(𝑠)
Dark blue indicates Fe2+
3𝐹𝑒 2+ + 2𝐹𝑒(𝐶𝑁)3−
6 → 𝐹𝑒3 (𝐹𝑒(𝐶𝑁)6 )2
Deep blood red indicates Fe3+
𝐹𝑒 3+ + 𝑆𝐶𝑁 − → 𝐹𝑒𝑆𝐶𝑁 2+
Topic 3 – Chemical Monitoring and Management
QUANTITATIVE ANALYSIS


There are a variety of techniques to determine the amount or concentration of an element, ion or
compound in the sample.
These techniques include:
o Gravimetric Analysis - involves weighing materials and determining the percentage composition
of elements
o Volumetric analysis - involves measuring the volume of solutions that react with other solutions
o Instrumental analysis - involves the use of special instruments that can determine the
concentration or amount of material by measuring a property of the material.
12.2 – INSTRUMENTAL ANALYSIS
ATOMIC ABSORPTION SPECTROSCOPY (AAS)



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Atomic vapours selectively absorb and emit various frequencies of light.
When a sample of an element is vapourised in a hot flame, electrons are promoted from the ground
state into unstable or excited energy levels.
As the electrons fall back to more stable levels they emit light through characteristic frequencies.
If white light is passed through an atomic vapour at a suitable low temperature, some wavelengths are
selectively absorbed and dark lines appear the in
the spectrum produced.
The dark lines correspond to the exact bright line
wavelengths in atomic emission spectra.
The AAS was developed by CSIRO scientist Alan
Walsh - AAS uses the exact principles as above.
This technique is very sensitive - it can detect
concentrations in part per million and parts per
billion.
HOLLOW-CATHODE LAMP SELECTION


The light source in the AAS is usually a hollow-cathode lamp of the element.
Specific wavelengths of light characteristic of the elements being analysed are generated from this lamp.
STANDARD SOLUTION PREPARATION

A standard solution of the metal being analysed is prepared using standard volumetric techniques.
ASPIRATING THE SOLUTIONS



The dilution standards and the unknown solution are sprayed or aspirated into the flame or graphite
furnace.
The flame in the AAS is about 1000C to increase absorbance of light.
The graphite furnace is about 3000C - it is more efficient.
MEASURING LIGHT ABSORPTION


As the light beam passes through the vapourised sample, some of the light is absorbed.
A second reference beam passes through a monochromator which contains a diffraction grating and
focussing mirrors.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management


The light then passes through a narrow slight to select only one of the wavelength bands - the light is
now monochromatic.
Photomultiplier tubes are used the measure the light intensity and convert it into an electrical signal.
CALIBRATION


Concentration measurements are determined from a calibration curve created with the standard
solutions.
A control blank is also run - it should indicate zero.
MONITORING TRACE ELEMENTS AND POLLUTANTS IN THE ENVIRONMENT
ESSENTIAL TRACE ELEMENTS



There are many elements that are needed in small quantities by plants and animals for the proper
function or their physiological processes.
There trace elements include copper, zinc, cobalt and molybdenum.
The advent of AAS has allowed for a deeper understanding of trace elements and its composition in
organisms and the environment.
Metal
Function
Copper
Haemoglobin formation and enzyme action
Zinc
Enzyme action, metabolism of amino acids and insulin synthesis
Selenium
Enzyme action
Manganese Enzyme action, blood clotting, carbohydrate and fat metabolism
Cobalt
Red blood cell formation
Chromium
Required for carbohydrate, fat and nucleic acid metabolism
Iodine
Proper functioning of the thyroid gland
USES OF AAS


AAS is capable of detecting the presence of well over sixty metals in minute concentrations.
It can be used for:
o To test the purity of metallic samples in the mining industry
o Monitor pollution levels in waste waters - especially heavy metals
o Detect harmful levels of metals in organisms
o Monitor dangerous air-borne metallic particles
o Quality control of alloys
o Detect minute contaminants in food
WHY MONITOR CATIONS AND ANIONS



Phosphate occurs in waterways at low concentrations and essential for normal aquatic plant growth.
At high concentrations can lead to:
o Algal bloom
o Covers surface of lake
o Prevents penetration of light - hence plants and fish die
o Algae dies when phosphate is used up
o Decay uses oxygen in water
Zinc and copper:
o Desirable in small concentrations in water bodies
o High concentrations are harmful to humans and cause poisoning
o Lead is poisonous - intellectually retards young children and causes brain damage.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
o
o
Was widely used in petrol
Was a constituent of house paint
CHAPTER 13 – ATMOSPHERIC CHEMISTRY
13.1 – CHEMISTRY OF ATMOSPHERIC POLLUTION AND OZONE DEPLETION
COMPOSITION AND STRUCTURE OF THE ATMOSPHERE

The atmosphere is a thin gaseous layer that extends to a distance of about 600 km above the Earth's
surface.
TROPOSPHERE









The troposphere is the layer closest to the ground.
75% of mass in concentrated in the troposphere.
The air pressure is also the highest - 100kPa on the ground.
At 15km altitude the air pressure
drops to 10kPa.
Temperature decreases with increase
altitude.
15C at the bottom and -50C to -60C
at the tropopause.
The transfer of gases of pollutants
across the tropopause is slow.
Water vapours freezes before
reaching the stratosphere as to
prevent water loss
The tropopause is at a higher altitude
above the equator than at the poles
due the expansion of air.
STRATOSPHERE









Air pressure continues to decrease with altitude and it drops to about 0.1kPa at the stratopause.
In the first 9km temperature is uniform but increases thereafter.
The ozone layer is situated within the stratosphere.
The greatest concentration is about 25km altitude
The higher layers of the ozone are warmer as they absorb UV-B and some UV-C rays.
There is a very little of mixing gases as temperature increase with altitude and prevents convection
currents.
Pollutants that enter remain for a long time
99.9% of Earth's atmosphere is present in the troposphere and stratosphere.
The average temperature is about -2C to 0C.
MESOSPHERE AND THERMOSPHERE




Air pressure continues to decrease from about 0.1kPa to 0.01kPa.
Temperature decreased with altitude to about -90C at the mesopause at 85km.
Above the mesosphere is the thermosphere.
Temperature rises again due to high frequency radiation.
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Topic 3 – Chemical Monitoring and Management



The thermosphere is about 600km thick.
The ionosphere is within this region.
Temperatures can reach 1700C.
COMPOSITION OF THE ATMOSPHERE


The concentration of total gas particles drop with increasing altitudes - proportions remains constant
The amount of water vapour in the atmosphere varies between 1-5%
Gas
Concentration
Nitrogen
78%
Oxygen
21%
Argon
0.9%
Carbon Dioxide 0.04%
Neon
0.002%
Helium
0.0005%
For most gases the concentrations are best expressed in parts per million - 1ppm = 1mL/kL
LOWER ATMOSPHERE POLLUTANTS


The atmosphere gets polluted by both natural processes and human activity.
Volcanoes release toxic gases and lighting produces nitrogen oxides and ozone.
Pollutant
Carbon Dioxide
Carbon Monoxide
Methane
Nitrogen Oxides (NOx)
Sulfur Dioxide
Chlorofluorocarbons
(CFCs)
Particulates
Ozone
Sources
Combustion of fossil fuels in industries and vehicles
Deforestation
Decomposition of organic matter
Incomplete combustion
Forest fires
Anaerobic decomposition of organic matter
Combustion of organic matter
Internal combustion engines
Factories
Internal combustion engines
Sulfide ore smelting
Some chemical manufacturing
Volcanic gases
Manufactured chemicals used in aerosols, refrigerants, foams and air conditioners
Dust - from industrial and domestic activity
Soot from fires, burn-offs
Photochemical smog
COORDINATE BONDING



Coordinate bonding is a special case of covalent bonding.
It is also commonly known as coordinate covalent bonding
A coordinate bond forms when one atoms provides both electrons for the shared pair
o Ammonium ions
 Forms when ammonia reacts with hydrogen ions
 Non-bonding pair of electrons on the nitrogen atom is shared with the hydrogen ion
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
o
Hydronium ions
 Oxygen atom in water has two non-bonding electron pairs
 Hydronium ions form when these non-bonding pairs are shared with a hydrogen ion.
o
Carbon monoxide
 Both covalent and coordinate bonds are
present in a carbon monoxide molecule
Ozone
 Ozone is a bent molecule
o
OXYGEN AND OZONE
Property
Colour
Odour
Molecular Shape
Melting and
Boiling Point
Density
Water Solubility
Effects on Life
Stability
Preparation
Oxygen
Colourless as a gas, but pale blue
when liquid or solid
Odourless
Linear
MP = -219
BP = -183
1.3g/L
Sparingly soluble, about 4.9mL O2
per 100mL
Essential for all living things
Very stable
Photosynthesis
Fractional distillation of liquid air
Decomposition of H2O2
Oxyacetylene welding
Liquid O2 as fuel for space
shuttles
Steel making
Medical uses for patients
Uses
Ozone
Pale blue as gas, deep blue when liquid and purple when
solid
Sharp, pungent
Bent
MP = -193
BP = -111
2.0g/L
More soluble than O2, dissolves readily into turpentine,
cinnamon oil and many other organic liquids
Poisonous and harmful, reactive with chemicals in living
tissue
Easily decomposed into O2
Effect of UV light on O2
Electric charge on O2
Germicidal actions
Bleaching agent in paper
Powerful oxidising agent
OZONE IN THE ATMOSPHERE

Stratosphere:
 Contains 90% of atmospheric
ozone
 Acts as primary UV radiation
shield
 Issues:
 Long-term downwards
trend
 Antarctic and Artic
ozone holes.
o In the stratosphere, the ozone acts like a UV shield.
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
o
UV radiation from the sun reacts with oxygen gas forming oxygen atoms that bond with oxygen
gas to form ozone.
𝑈𝑉, 240𝑛𝑚
𝑂2(𝑔) →
2𝑂(𝑔)
𝑂2(𝑔) + 𝑂2 → 𝑂3(𝑔)
o
o
Most ozone is made above the equator as sunlight is most direct.
Ozone can absorb harmful UV-B and UV-C radiation.
𝑈𝑉, 200−300𝑛𝑚
𝑂3(𝑔) →
o
𝑂2(𝑔) + 𝑂(𝑔)
Ozone can be decomposed using oxygen atoms
𝑂3(𝑔) + 𝑂(𝑔) → 2𝑂(2)

Troposphere:
 Contains 10% of atmospheric ozone
 Toxic effects on humans and vegetation
 Effects on humans include:
 Irritation to eyes
 Increased respiratory conditions
 Compromised lung functions
 Increase susceptibility to infection
 Issues:
 High surface ozone in urban and rural areas
o Formed during electrical discharge - such as sparks from photocopiers, overhead power lines and
lightening
𝑂2(𝑔) → 2𝑂(𝑔)
𝑂2(𝑔) + 𝑂(𝑔) → 𝑂3(𝑔)
o
o
Ozone forms in the lower atmosphere where there are:
 Sunlight
 Nitrogen dioxide
NO and NO2 are produced in high temperatures of internal combustion engines - hence catalytic
converters are used.
𝑈𝑉, 𝑠𝑢𝑛𝑙𝑖𝑔h𝑡
𝑁𝑂2(𝑔) →
𝑁𝑂(𝑔) + 𝑂(𝑔)
𝑂2(𝑔) + 𝑂(𝑔) → 𝑂3(𝑔)
o
o
The oxygen radical is reactive and can readily bond with other molecules.
However, nitric oxide, NO, can destroy ozone.
𝑁𝑂(𝑔) + 𝑂3(𝑔) → 𝑁𝑂2(𝑔) + 𝑂2(𝑔)
o
o
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Unburnt hydrocarbons mixed with ozone forms a toxic photochemical smog.
Ozone is the most harmful, by greenhouse gases readily react with other gases, so ozone doesn't
remain in the atmosphere for that long.
By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
OXYGEN AND THE OXYGEN FREE RADICAL







Oxygen atoms have six electrons in their outer shell.
When oxygen is passed through electrical discharge or UV radiation, the oxygen molecule splits, forming
oxygen atoms.
The atoms have two paired and unpaired electrons.
o This makes the atom unstable and reactive
o They are called oxygen free radicals
The unpaired electrons exist in higher energy states than the ground state.
They exist only briefly in the lower layers of the atmosphere.
In the thermosphere, oxygen free radicals are formed when far UV photons cause photodissociation of
oxygen molecules
Oxygen free radicals are even more reactive than ozone.
HALOALKANES, CHLOROFLUOROCARBONS AND HALONS


When alkanes react with halogens, they form new compounds that are known as haloalkanes.
Haloalkanes often exist in isomeric forms - the variable location of the halogen within the molecule leads
to the formation of isomers
CHLOROFLUOROCARBONS




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
Chlorofluorocarbons (CFCs) and halons are examples of haloalkanes.
CFCs are alkanes containing only fluorine and carbon.
They are alkanes that only have chlorine and fluorine atoms instead of hydrogen.
Halons contain bromine atoms in addition to the chlorine and fluorine atoms in CFCs.
CFCs are odourless, non-toxic, non-flammable, inert substances.
CFCs were developed in the 1930's to replace ammonia in refrigerators.
They were then extensively used as:
o Refrigerants
o Solvents in dry cleaning
o Propellant in spray cans
o Blowing agents for expanded plastic products
Halons are dense, non-flammable liquids.
Halons are used in extinguishers especially for electrical fires.
STRATOSPHERIC OZONE DEPLETION


CFCs are stable and insoluble; hence they
stay in the troposphere and eventually
into the stratosphere.
In the stratosphere they come into
contact with short wave UV radiation and
undergo photodissociation.
o Photodissociation breaks a
chlorine atom off the CFC
molecule.
𝑈𝑉
𝐶𝐶𝑙3 𝐹 → 𝐶𝑙∎ + ∎𝐶𝐶𝑙2 𝐹
𝑈𝑉
𝐶𝐶𝑙2 𝐹2 → 𝐶𝑙∎ + ∎𝐶𝐶𝑙𝐹2
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management

The free chlorine atom can now catalyse the reaction of ozone to oxygen.
𝐶𝑙∎ + 𝑂3 → 𝐶𝑙𝑂∎ + 𝑂2
𝐶𝑙𝑂∎ + 𝑂∎ → 𝐶𝑙∎ + 𝑂2

Hence the overall reaction is:
𝑂 + 𝑂3 → 2𝑂2

The free chlorine atom is able to continue this process hundreds of times before it gets removed by some
other species.
𝐶𝐻4 + 𝐶𝑙∎ → 𝐶𝐻3 ∎ + 𝐻𝐶𝑙
𝑁𝑂2 + 𝐶𝑙𝑂∎ → 𝐶𝑙𝑂𝑁𝑂2


This chain reaction is important because one CFC molecule can destroy countless numbers of ozone
molecules and can cause significant damage.
The dramatic depletion of stratospheric ozone has been observed only over the Antarctic and then only
in spring.
STRATOSPHERIC OZONE DEPLETION


In 1976, a British Antarctic Survey noted a 10% drop in ozone levels in the stratosphere over Antarctica in
the southern spring.
o It was unusual as levels have remained the same since 1957.
o Initially this data was treated as an outlier
o In 1983, ozone depletion was of mass concern as they observed record losses of ozone that
spring.
Measurements:
o In 1985, measurements over Antarctica showed a 50% reduction in ozone concentrations over the
past 10 years.
o The results were recorded by the total ozone mapping spectrometer (TOMS) and solar
backscatter ultraviolet detector.
o Another technique is through the use of UV lasers - UV laser light is fired into the sky, the level of
absorption determines the level of concentration.
THE "OZONE HOLE"






The thinning of the ozone layer results in what is known as an
"ozone hole".
During 1987, the ozone hole spread over southern Australia
and New Zealand.
Further depletions were recorded in the 1990’s; the worst was
in 2003, 2000 and 1998.
The ozone hole is not confined to the Antarctic, with small
decreases over the Artic too.
By 1996, the thinning of ozone over the Arctic reached 40%.
Decreased concentrations of ozone are a problem as:
o More UV rays would reach the ground
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By: Raymond Chen
Topic 3 – Chemical Monitoring and Management
o
o
o
o
o
16
Phytoplankton and zooplankton would be affected
The food chain in the end would be affected too.
Skin cancer rates have increased by 66% over 14 years in world's most southernmost city.
Causes respiratory conditions
Damage and cause mutations of DNA.
By: Raymond Chen