module 3 chemical monitoring and management

HSC Chemistry Module 3: Chemical Monitoring and managementSummary

Page | 1Robert Lee Chin

Chemical Monitoring and Management: 1. Chemical Scientists

Gather, process and present information from secondary sources about the work ofpracticing scientists identifying:

-the variety of chemical occupations -a specific chemical occupation for a more detailed study

Range of Chemical occupationsThe Royal Australian Chemical Institute (RACI) has thirteen national divisions formembership:

-Analytical-Biomolecular-Cereal-Chemical education-Colloid and surface science-Environment-Industrial-Inorganic-Electrochemistry-Organic-Physical-Polymer-Solid state

Outline the role of a chemist employed in a named industry or enterprise,identifying the branch of chemistry undertaken by the chemist and explaining achemical principle that the chemist uses

Laboratory ToxicologistBranch of chemistry Analytical ChemistryCompany UK based AltrixWhat is atoxicologist?

A scientist who specialises in identifying, controlling and preventingthe effects of chemicals on human health.

They may work in natural environments, industry or laboratories.They can be employed in a hospital lab, university, governmentagency, private research organisation or corporate employers.

Generally, they conduct tests on toxic or radioactive chemicals, takecareful notes and write detailed reports on their findings in order toset new industry standards or environmental protection laws

Role of Altrix labtoxicologists

Altrix lab toxicologists provide drug-testing services to governmentand corporate employers who need to screen job applicants forevidence of drug abuse or infectious diseases e.g. hepatitis. Labtoxicologists must be able to:



-work as part of a multi-disciplinary team

-participate in special research projects and activities

-comply with Good laboratory Practice and OH&S procedures.

The company uses a non-evasive mouth swab of hair sample and ahigh-tech method of gas chromatography and mass spectrometry.The toxicologist also needs to report the results back to the client andbe prepared to appear as ‘expert witness’ in a legal challenge.

Lab toxicologists need to collaborate by:

-comparing analysis results with results obtained by team members

to confirm the validity of the results

-discuss results and conclusions with other professionals.

-managing the usage of equipment, scheduling of tests and deadlines

-keep up to date with new developments by communicating with

other scientists, attending seminars and conferences

Chemical Principle:Gas Chromatography

Samples are first dissolved in a suitable solvent. The samples areinjected into a chromatography column which vaporises the sample.A stream of inert ‘carrier gas’ (e.g. helium) carries it through thecolumn. Different molecules ‘adsorb’ at different rates and arepicked up by a sensitive electronic detector and sent to a computerfor analysis.

Identify the need for collaboration between chemists as they collect and analyse data



Real chemists rarely work alone. Most chemists have expertise in only a specialised field andmust therefore cooperate, communicate and collaborate with both their colleagues and clients.

Describe an example of a chemical reaction such as combustion, where reactantsform different products under different conditions and thus would need monitoring

Many chemical reactions are sensitive to any change in conditions i.e. temperature, pressure,concentration, catalysts.

As a specific example, consider the effect of oxygen availability on the combustion of naturalgas , which is mostly methane:

Complete combustionIf there is a good supply of oxygen, methane will undergo complete combustion, formingcarbon dioxide gas and water:

Incomplete CombustionIf there is a shortage of oxygen, incomplete combustion will occur, forming carbon monoxideor carbon (soot):

Incomplete combustion is undesirable (esp. in industry and in internal combustion engines)because:

-Less energy is released per unit of fuel used-carbon monoxide is toxic-soot clogs up equipment

ManagementA chemical engineer could monitor combustion by:

-measuring the flow, and mixing of air and fuel-measuring combustion temperature-measuring exhaust gas composition

2. Maximise Production

Identify and describe the industrial uses of ammonia

Ammonia ranks second to sulfuric acid in terms of quantity produced worldwide per year. Itis one of the world’s most important industrial chemicals. In particular, it is used in themanufacture of:



-explosives -dyes and pigments -fibres and plastics (e.g. rayon, nylon)

-household cleaners and detergents-pharmaceuticals-fertilisers (ammonium nitrate, urea, sulfate of ammonia)

The common fertiliser “sulfate of ammonia” is produced industrially by reacting sulfuric acidwith ammonia in an acid-base reaction:

Ammonia gas is also used as a refrigerant.

Gather and process information from secondary sources to describe the conditionsunder which Haber developed the industrial synthesis of ammonia and evaluate itssuccess at that time in world history

History: Development of Ammonia Synthesis (aka “The Haber Process”)Prior to WW1, Nitrogen compounds were essential to manufacture fertilisers and explosives(e.g. TNT, dynamite, ammonium nitrate). This was largely dependent on the supply of natural“saltpetre” deposits (sodium nitrate) from Chile (and to a lesser extent, guano andammoniacal liquor). It was known that the atmosphere contained large quantities of diatomicnitrogen. Thus, a cheap, large-scale process would be advantageous to convert this into usefulcompounds for agriculture and industry.

In 1908, German chemist Fritz Haber developed a laboratory method to synthesise ammoniafrom hydrogen gas and atmospheric nitrogen gas in the lab, using an iron catalyst. Carl Boschlater developed the high pressure technology required for this process on an industrial scale.

Nitrogen is readily available from air and hydrogen gas could be obtained from hydrocarbons.This removed Germany’s dependence on mining and shipping from Chile.

A process called the Ostwald process was then used to convert the ammonia into nitric acidand nitrates. This was hugely important at the time because Europe was on the brink ofWW1- explosives and food supplies were to become critical.

During WW1, the British cut off Germany’s supply of saltpetre from Chile, however, theHaber process allowed Germany to be self-sufficient in producing ammonia for fertilisers andexplosives. This was successful in allowing Germany to lengthen the war, thereby leading tomore human suffering and destruction.

However, the Haber process also led to the development of many useful products, includingfertilisers (food for ↑ world population), explosives and textiles, which we take for grantedyet depend on every day.

Identify that ammonia can be synthesised from its component gases, nitrogen andhydrogen

The Haber process is still used for the industrial synthesis of ammonia. Under pressure andheat, nitrogen and ammonia gas react in the molar volume ratio 1:3 to produce 2 molarvolumes of ammonia gas:



Describe that synthesis of ammonia occurs as a reversible reaction that will reachequilibrium

Identify the reaction of hydrogen with nitrogen as exothermic

The synthesis of ammonia is a reversible reaction. This means once some ammonia isproduced (forward reaction), some nitrogen and hydrogen are also produced (reversereaction). Under normal pressure and heat, the rate of reaction is slow and the equilibriumyields little ammonia.

It is also exothermic, producing 46kJ of heat for every mole of ammonia produced:N2(g)+3H2(g) 2NH3(g) + heat ΔH=-92kJ

Explain why the rate of reaction is increased by higher temperatures

Increasing temperature increases the speed and kinetic energy of the particles. This increasesthe frequency of collisions and also the amount of energy available for the reaction. Most ofthe increased rate of reaction comes from the colliding particles exceeding the activationenergy. The rate of both the forward and reverse reaction is increased.

Explain that the use of a catalyst will lower the reaction temperature required andidentify the catalyst(s) used

Using a catalyst reduces the activation energy required. At a given temperature a catalystincreases the likelihood that particle collisions will exceed the activation energy. The catalystused in the Haber process is the iron mineral “magnetite” (Fe3O4), with the surface reducedto elemental iron. The catalyst is finely ground to increase surface area. Gaseous nitrogen andhydrogen molecules adsorb to the iron catalyst, forming ammonia.

Explain why the yield of product in the Haber process is reduced at highertemperatures using Le Chatelier’s principle

The forward reaction is exothermic. According to Le Chatelier’s principle, if a system atequilibrium is disturbed, the system will shift to minimise the change. Thus increasing thetemperature shifts the equilibrium to the left and the yield of ammonia is reduced.

Analyse the impact of increased pressure on the system involved in the Haberprocess

Increased pressure causes the equilibrium to shift to the right, increasing the yield ofammonia. By Le Chatelier’s principle, the system will favour the right side because theproduct (2 moles of ammonia gas) takes up less volume than the reactants (1 mole of nitrogenand 3 moles of hydrogen gas).

N2(g) + 3H2(g) 2NH3(g)4 moles 2 moles



Increasing pressure also increases the rate of reaction because the gas molecules are forcedcloser together.

To reach an economic yield, H2 and N2 gases are pumped in at the ideal mole ratio of 3:1under pressure of 15-25MPa.

Explain why the Haber process is based on a delicate balancing act involvingreaction energy, reaction rate and equilibrium

Today, the Haber process is performed using atmospheric nitrogen and hydrogen obtained byreacting steam and methane, using a nickel catalyst:

Increasing reaction temperature increases the energy available to overcome the activationenergy and hence the rate of reaction increases. However, increasing temperature also favoursthe decomposition of ammonia gas (Le Chatelier’s principle). A compromise is 400°C.

To achieve an economic yield of 30%, the following conditions are used:-1:3 ratio of nitrogen to hydrogen-pressures of 15-25MPa-Temperature of 400°C-500°C-Iron oxide (Fe3O4) catalyst-Unreacted gases are returned to the reaction vessel-ammonia is constantly removed as a liquid

Explain why the monitoring of the reaction vessel used in the Haber process iscrucial and discuss the monitoring required.

The raw materials must be monitored to ensure they are clean. Any CO2 detected must beremoved (it is often diverted to a nearby fertile plant for urea manufacture). Any O2 presentcould result in an explosion with the hydrogen.

The catalyst surface has to be monitored to ensure maximum adsorption of the reactant gases.Contaminants i.e. carbon monoxide and sulfur compounds can damage the catalyst, as can toohigh temperatures.

A chemical engineer monitors the reaction vessel to ensure the temperature and pressureconditions, levels of contaminating gases and ratio of reactant gases are maintained within anacceptable range.



3. Manufactured products are analysed

Deduce the ions present in a sample from the results of tests



Solubility RulesThe following are soluble: All salts of group I metals All salts formed by the ammonium ion All nitrates and acetates



All chlorides, bromides and iodides EXCEPT those of silver, lead and mercury All sulfates EXCEPT lead, barium, mercury and strontium (calcium and silver sulfates

are only slightly soluble)

The following are insoluble: All carbonates, hydroxides and phosphates EXCEPT those of Group 1 and ammonium

Solubility TableCations Anions

phosphate sulfate carbonate chloride hydroxide nitrateBarium White White White WhiteCalcium White White

(slightlysoluble)

White

Lead white White White white WhiteCopper Blue-green Bright blue to

greenPale blue

Iron (II) Green Yellow/gold WhiteIron (III) ? Yellowsilver Yellow White

(slightlysoluble)

yellow White,darkens in

light

White

Perform first hand investigations to carry out a range of tests, including flame tests,to identify the following ions:

-phosphate-carbonate-chloride-barium-Calcium-Lead-Copper-Iron

Experiment: Test for cationsAim: to carry out flame tests and a series of chemical reactions in order to devise tests foridentifying the following cations in solution when these are the only ions that could bepresent.

Cations:Ba2+ Pb2+

Cu2+ Ca2+

Fe2+ Fe3+



Equipment:A Flame Tests5 mL concentrated (6 M) HClPlatinum or nichrome wireSmall beakerBunsen burnerTongsSmall samples of:

-Nitrates of barium, calcium, copper, iron(II), -Chlorides of barium, calcium, copper, iron(II), iron(III)

B Precipitation reactionsDropper bottles, each containing one of the following 0.1molL-1 solutions:

Cation Solutions

Pb(NO3)2Ba(NO3)2FeSO4CuSO4CuSO4CaCl2FeCl3

Safety:-Wear safety glasses and protective aprons-Concentrated NaOH and HNO3 are corrosive. Do not allow direct contact with skin orclothes. If contact occurs, wash with large amounts of water for 10-15 min-Do not touch heated wire-metal salts are poisonous. Avoid direct contact with skin or eyes-Dispose of chemicals as directed by teacher

Method:A Flame TestsNote: Not all metal ions produce distinctive colours

1/ Clean wire thoroughly using a small amount of concentrated HCl, then heatingstrongly. Repeat until no further colouration of flame.

2/ Dip wire into clean, concentrated HCl, then into one of the solids. Place in flame andobserve flame colour

3/ Repeat steps 1-2 for each solid, cleaning wire thoroughly in between each compound.

B Precipitation Reactions

Test solutions

Na2SO4 6 test tubesHCl 5 mL HCl (6 M)NaOH Test tube rackAmmonia solution Distilled waterAcidified KMnO4NaF



1/ Add 10 drops of each cation to each of the 6 test tubes

2/ Add 10 drops of the Cl- solution to each test tube. If no precipitate forms, add a fewmore drops. Record results

3/ Thoroughly clean all test tubes with distilled water

4/ Repeat steps 1-3 for SO42-

5/ Repeat steps 1-3 for OH-, if precipitate forms add excess OH-

6/ Repeat steps 1-3 for OH-, if precipitate forms add excess NH3

7/ Add 10 drops of Fe2+ and Fe3+ solutions to separate test tubes. Add 10 drops ofSCN- to each test tube. Record the results.

8/ Add 10 drops of Fe2+ and Fe3+ solutions to separate test tubes. Add 10 drops ofMNO4- to each test tube. Record the results.

8/ Add 10 drops of Ca2+ solution to a test tube and add 10 drops of F- solution. Recordthe results.

8/ Add 10 drops of Pb2+ solution to a test tube and add 10 drops of I- solution. Recordthe results.

Results:A Flame Test

Compound Ions present in compound Flame ColourBarium Nitrate [Ba(NO3)2] Ba2+ Red-orange

Bariumnitrate

Leadnitrate

Coppersulfate

Iron (II)sulfate

Calciumchloride

Iron (III)chloride



Calcium nitrate [Na(NO3)2] Ca2+ Apple greenCopper nitrate [Cu(NO3)2] Cu2+ blue greenIron (II) nitrate [Fe(NO3)2] Fe2+ -Barium chloride [Ba(Cl)2] Ba2+ Blue greenCalcium chloride [Ca(Cl)2] Ca2+ Red orangeCopper chloride [CuCl2] Cu2+ Apple greenIron (II) Chloride [FeCl2] Fe2+ -Iron (III) chloride [FeCl3] Fe3+ -

B Precipitate Reactions

Testcations

Cl- SO42- OH- Excess OH- ExcessNH3

Additionaltests

Pb2+ White ppt White ppt White ppt Pptdissolves

Whiteppt

Yellow pptwith I-

Cu2+ Pale blueppt

Clear bluegel

Pptdissolves

Ba2+ White ppt

Ca2+ White ppt White pptwith F-

Fe2+ Green ppt,turns brown

DecolourisesacidifiedMnO4-

Fe3+ Brown gel Redcomplexwith SCN-

Cation Test and resultLead Gives white ppt with Cl- and with SO42-; with OH- gives white ppt which

dissolves in excess OH-. Forms yellow ppt with addition of I-.Copper No ppt with Cl- or SO42- but with OH- gives pale blue ppt which dissolves

in excess NH3Barium Gives white ppt with SO42- but not with Cl- or OH-Calcium Gives white ppt with F- but no ppt with Cl-, OH- or SO42-

Iron (II) No ppt with Cl- or SO42- but ppt with OH-; decolourises acidified MnO4Iron (III) No ppt with Cl- or SO42- but ppt with OH-; forms red colour with SCN-

Experiment: Tests for anions



Aim: To carry out a series of chemical reactions in order to devise tests for identifying thefollowing cations in solution when these are the only ions that could be present.

Anions:PO43-

SO42-

CO32-

Cl-

Equipment:Dropper bottles containing one of the following 0.1molL-1 solutions:

Test Solutions-Pb(NO3)2-Ba(NO3)2-HNO3-AgNO3-NaOH4 test tubes

Safety:-Wear safety glasses and protective aprons-Concentrated NaOH and HNO3 are corrosive. Metal salts are poisonous- do not allow eitherto directly contact skin or eyes-Silver nitrate stains clothes and skins brown-Dispose of chemicals as directed by teacher

Method:

1/ Add 10 drops of each of the anion solutions to each of 4 test tubes

Anion SolutionsNa2SO4Na2CO3Na3PO4NaCl

Test tube rack

Sodiumcarbonate

Sodiumsulfate

Sodiumphosphate

SodiumChloride



2/ Add 10 drops of HNO3 to each of the test tubes and warm gently.

3/ Record results and use to describe a test for a particular anion.

4/ Thoroughly clean all test tubes with distilled water between tests

5/ For the remaining three anions, put 10 drops in each of 3 test tubes, add 5 dropsHNO3 and then 5 drops of Ag+. Record results

6/ Repeat steps 4-5 with Pb2+ and Ba2+

7/ After the Ba2+ test add 10 drops of NaOH to each of the test tubes and record anychanges.

Results:Test

anion/solution

H+ Ag+ Pb2+ Ba2+ andH+

Ba2+ &OH-

CO32- Gas bubbles n/A

Cl- White ppt n/A

SO42- White ppt

PO43- White ppt

Anion Test and resultChloride Precipitate with acidified Ag+, but not with Ba2+Sulfate Precipitate with acidified Ba2+Phosphate Precipitate with Ba2+ in alkaline solution, but not in acid solutionCarbonate Produces bubbles of gas with addition of HNO3



Gather, process and present information to describe and explain evidence for theneed to monitor levels of one of the above ions in substances used in society

Certain human activities release harmful ions into the environment. It is therefore essential tomonitor the levels of these ions in the air, soil, water and food to protect people and theenvironment

Phosphate IonsAt normal concentrations, phosphate ions (PO43-) form an essential part of the naturalenvironment.

Human activities such as fertiliser run-off from agriculture and sewage discharge intowaterways have increased phosphate concentrations in water environments. Also, water usedin irrigation reduces the water flow, making the problem more likely.

Increased phosphate concentrations result in eutrophication, a process in where aquatic plantsand algae are “over-fertilised” and grow excessively. This clogs waterways and when theplant life dies and rots, it takes the oxygen out of the water, putrefying it and killing theecosystem.

Lead IonsLead is a toxic metal, not normally found in the natural environment in significant amounts.Even low concentrations are dangerous because it accumulates in the body until it reachestoxic levels. Lead poisoning results in neurological diseases in humans.

Lead compounds used to be present in paints and petrol. Lead based petrol is a particularconcern as it releases lead fumes into the air. To reduce the environmental impact, lead-basedpaints were banned and unleaded petrol introduced. Lead emissions from industry are alsomonitored now. Previous lead emissions still require monitoring as the lead persists in theenvironment for long periods.

Analyse information to evaluate the reliability of the results of the aboveinvestigation and to propose solutions to problems encountered in the procedure.

The reliability of any analysis can be assessed by how close the results are when the methodis repeated. Results can be considered reliable when various group results are in closeagreement.

The major difficulty in separating solid barium sulfate (BaSO4) is the very small crystal size.Ordinary filtration using filter paper is ineffective. One solution is to use a sintered glasscrucible and vacuum filter.

Gather, process and present information to interpret secondary data from AASmeasurements and evaluate the effectiveness of this in pollution control



Case Study: Arsenic concentrations in BangladeshArsenic in groundwater poses a health hazard to over 20 million people in Bangladesh. Solaroxidation and removal of arsenic (SORAS) is a technique that uses irradiation of water withsunlight in UV transparent bottles to reduce arsenic in drinking water.

Groundwater in Bangladesh contains both Fe2+ and Fe3+ ions. Fe3+ forms a precipitate [Iron(III) hydroxide)] with OH-. Arsenic (III) is only weakly adsorbed to this precipitate butarsenic (V) is strongly adsorbed.

SORAS involves adding lemon juice to a litre of water in a PET bottle. Adding acid speedsup the photo-oxidation process. The bottle is placed into sunlight for 4-5 hours where UVlight, oxygen and water in the bottle oxidises As (III) into As (V) and Fe2+ into Fe3+:

The precipitate is allowed to settle and the clear liquid is decanted off.



Groundwater Sample Absorbance Concentration(μgL-1)

Daily adult intake(safe daily intake: 150μg and 2L water/day)

Before SORAS 0.28 121.74 243.48After SORAS 0.13 56.52 113.04

Describe the use of atomic absorption spectrometry (AAS), in detectingconcentrations of metal ions in solutions and assess its impact on scientificunderstanding of trace elements

When particular samples of atoms are energised, they emit light of a characteristic frequency,producing a characteristic absorption spectrum. The amount of light emitted is usually toosmall for measuring minute concentrations. The exact frequencies of light emitted by an atomare also the same frequencies that atom will absorb and this is more easily measured.

AAS is a technique for determining the concentration of a particular element, usually a metalin a sample. It involves beaming light (of the frequency the target atom will absorb) through avaporised sample, which reemits it in all directions. A detector absorbs the light and measuresthe intensity. The amount of light absorbed is directly proportional to the number of ‘target’atoms present, so it measures it quantitatively.



The electronic detector interprets the data as a pattern of narrow bright bands called anabsorption spectrum. Each different element has its own unique absorption frequencies andtherefore, absorption spectrum. The light emitted by a sample shows very narrow bright lineson a dark background, because only specific frequencies are emitted. Because the targetelement will also absorb these same frequencies, the light absorption spectrum shows darklines on a bright background. The relative intensity and pattern of the absorption spectrumindicates the concentration of the element.

Impact on scientific understanding oftrace elementsThe study of pollutant concentrations in the environment is more accurate and reliable sincethe development of AAS by CSIRO scientist, Alan Walsh, in the 1950s. It is used areas, suchas medicine, agriculture, mineral exploration, metallurgy, food analysis, biochemistry andenvironmental monitoring. It has been described as the most significant advance in chemicalanalysis of the 20th Century and can be used for over 65 elements.Trace elements are elements essential in trace amounts to living organisms. AAS enabled themeasurement of the concentrations of many metals in the bodies of plants and animals and intheir surrounding environments.

Fuel andair

Flame vaporisessample. Target atoms

absorb specificfrequency light

Lamp containingelement to be analysedbeam

Electronicdetector

Sample

Optical system toselect and

intensify specificfrequency light

Emission Absorption



In WA, farmers found their sheep were chronically sick, despite good pastures and diseasecontrol. AAS showed cobalt deficiencies in the soil and the pasture. Further studies showedthat all animals require cobalt for enzyme production. The sheep were given a slow releasecobalt ‘pill’ and the multi-million dollar industry was saved.

Arid areas of Victoria could not support legumes until molybdenum deficiencies weredetected by AAS.

Identify data, plan, select equipment and perform first-hand investigations tomeasure the sulfate content of lawn fertiliser and explain the chemistry involved

Investigation: Determination of sulfate in lawn fertiliser

Aim: To gravimetrically determine the m/m % of sulfate in a typical lawn fertiliser

Equipment:-Burette and pipette-retort stand and clamp-electronic scale-Ammonium sulfate [(NH3)2SO4] fertiliser-dilute HCl-0.2 M BaCl2 solution-2 x 250mL beakers-sintered glass filter-250 mL vacuum flask

Method:1/ Accurately weigh ≈2 g fertiliser sample

2/ Dissolve in excess (about 100mL) HCl

3/ Filter to remove any insoluble material

4/ Slowly add excess BaCl2 (about 100ml), stirring well.

4/ Filter using sintered glass filter and vacuum flask to remove solid BaSO4. Rinseresidue with pure water

Mixture

Suction

Filtrate



5/ Dry residue in an oven and weigh

Results

4. Human Activity and the Atmosphere

Describe the composition and layered structure of the atmosphere

StructureThe atmosphere consists of two main layers: the troposphere and the stratosphere.

The troposphere extends up to an altitude of 15km. In the troposphere are over 90% ofEarth’s gases and the temperature drops with altitude. The top of the troposphere is known asthe tropopause and the temperature is stable. Above the troposphere is the stratosphere, wheretemperature rises with altitude.



CompositionWater vapour varies from 0.5-1.0%, but other gases remain in constant. In dry air:Nitrogen ≈78.1%Oxygen ≈20.9%Argon ≈00.9%

This represents 99.9%. The remaining 0.1% consists of carbon dioxide, inert gases, methaneand ozone. Despite the small concentrations, these gases are of most concern.

-100 -80 -60 -40 -20 0 20

Troposphere

0

10

20

30

40

50

60

70

80

90

100

Altitude (km)

Thermosphere Ionosphere

Ozonelayer

Stratosphere

Mesosphere

Highest concentration of ozone

Mr. Everest

Temperature (°C)

1.0 atmosphere

0.1 atmospheres

0.001 atmospheres



Identify the main pollutants found in the lower atmosphere and their sources

Pollution Artificial Sources Natural sourcesNitrogenoxides, NOx(NO, NO2)

Motor vehiclesElectricity production

Action of sunlightSoil bacterialightning

Volatileorganiccompounds

Unburnt fuel, solvents, thinners,alcohols, paints, hydrocarbons

Emitted by vegetation e.g.eucalyptus oil

Carbonmonoxide, CO

Incomplete fuel combustion (vehicles,smelters, power stations)

Incomplete biomass combustion(volcanic eruptions, decomposingorganic matter)

Carbondioxide, CO2

Combustion of fuels for transport andelectricity productionSmelting of metals

Respiration of plants and animalsVolcanoesBushfiresDecomposition of organic matter

Sulfur Dioxide,SO2

Smelting of metalsIndustrial production of sulfuric acidIncineration of waste productsPetroleum refineries

Soil bacteriaVolcanoes

Particles Combustion of fossil fuelsMining (underground and open cut)

Burning biomassSoil from erosionPollen and sporesAgricultural and industrial practices

Lead Lead smeltingLeaded motor vehicles from the 80’sOld batteries

Erosion of lead ores

Ozone Photochemical smogElectric discharge in DC motorcommutators

Action of UV light on atmosphere

Describe ozone as molecule able to act both as an upper atmosphere UV radiationshield and a lower atmosphere pollutant

In the upper atmosphere (stratosphere), where concentrations of ozone are up to 8 ppm, itprotects us against dangerous UV radiation. Up to 90% of all UV is absorbed by the ozonelayer.

In the lower atmosphere (troposphere), ozone is a toxic pollutant. Ozone is highly reactive,capable of oxidising many substances. Concentrations as low as 0.2 ppm cause lung damage,life-threatening for asthma suffers.



Ironically, human activities destroy ozone in the stratosphere and produce ozone in thetroposphere. Describe the formation of a coordinate covalent bond

Non-metallic compounds contain covalent bonds. A covalent bond is formed by a sharedpair of electrons. A coordinate covalent bond forms when one atom provides both theelectrons for the covalent bond. Otherwise, the bond is indistinguishable from a normalcovalent bond.

Demonstrate the formation of coordinate covalent bonds using Lewis electron dotstructures

Ozone, O3To form ozone, another oxygen atom must bond to the O2 molecule. The middle oxygenatom provides both the electrons for the single covalent bond with the third oxygen atom.

Sulfur dioxide, SO2The sulfur atoms supplies both pairs of electrons to form the coordinate covalent bonds

Sulfur Trioxide, SO3In SO2, the sulfur has a pair of free electrons. It is possible for an oxygen atom to form acoordinate covalent bond here. Note that the sulfur only needs 6 electrons to have a‘complete’ shell.

Sulfate ion, SO42-As shown in SO3, the sulfur only needs 6 electrons

for a complete shell. If two electrons are added (maybe from a metal), they can form anothercoordinate covalent bond.

Hydronium Ion, H3O+A proton forms a coordinate covalent bondwith the oxygen from the water molecule

O O OO OO

S

O

O O S

O

O

O S

O

OO S

O

O

O S

O

OO

O

O S

O



Ammonium Ion, NH4

Compare the propertiesof the gaseous forms of oxygenand the oxygen free radical

Compare the properties of the oxygen allotropes O2 and O3 and account for themon the basis of molecular structure and bonding

O2 (oxygen gas) O3 (ozone) O(oxygen freeradical)

Colourless odourless gas Pale blue, toxic gas withsharp, pungent odour

Oxygen atom withunpaired electrons andenergy levels higherthan ground state

Moderately reactive. Decomposed byhigh-energy UV light

Highly reactiveDecomposed by mediumenergy UV light

Extremely reactive

Formed by photosynthesis Formed by UV andelectric discharge onoxygen

Formed by UV lighton oxygen and also onozone

Essential for life Causes coughing chestpain and rapid heartbeatConcentration greaterthen 1ppm is toxic

Highly reactive withchemicals in livingcells

M.P.B.P. Density (liquid at20°C)

218.75°C-182.96°C1.331gL-1

-192.5°C-110.5°C1.998 gL-1

\

Diatomic molecule i.e. 2oxygen atoms heldtogether by a covalentdouble bond

Three oxygen atoms heldtogether with 1 double covalentbond and 1 single covalent bond

Each radical contains twounpaired valence shellelectrons

H O

H

HH O

H

H+

H+N HH

H

N

H

HH

H



Linear molecule Bent molecule, due to electronpairs getting as far away fromeach other as possible

Single atom in molecule

Explanation of differences between O2 and O3The differences are due to bonding and structure.

Differences in physical properties are due to the larger size of the O3 molecule, whichincreases dispersion forces between molecules

The differences in reactivity are due to bonding. The double covalent bond in O2 is strong,

requiring 500 kJmol-1 to exceed the activation energy. In contrast, it only takes 100 kJmol-1to break any of the bonds in O3, so it readily enters oxidation reactions. This is because thetwo covalent bonds consist of a single and a partial bond.

Oxygen Free radicals and ozone formationIn the stratosphere, UV radiation causes O2 molecules to split into separate oxygen atomscalled “oxygen free radicals”. The energy absorbed in splitting and the unpaired electronsmake them extremely reactive.

Although oxygen free-radicals are highly reactive, most gases in the atmosphere areunreactive. Nitrogen molecules are stable, argon is completely inert and O2 is relativelyreactive. So oxygen free radicals react with O2 molecules to form ozone. Because ozone hasnothing to react with, it can reach concentrations of up to 8 ppm.

Paradoxically, the UV radiation which creates oxygen free-radicals and thus, ozone, arestrongly absorbed (over 90%) by ozone.

Identify the origins of chlorofluorocarbons (CFC) and halons in the atmosphere

Alkanes of alkenes with a halogen replacing a hydrogen are named haloalkanes orhaloalkenes. Halogens often involved are Br, I, Cl & F.

Chlorofluorocarbons (CFCs) are a group of haloalkanes containing fluorine & chlorine andare responsible for destroying the ozone. Halons are fluorocarbon compounds containingbromine which are even more destructive to the ozone than CFCs.

OO O



CFCs were first used as refrigerants in the 1930’s as a ‘safer’ alternative to ammonia. Theirproperties of inertness and low boiling point led to many uses including, dry cleaning fluids,solvents, insecticides (e.g. DDT), propellants, fire extinguishers and foam blowing agent

Halons were used in fire extinguishers to protect against electrical fires. Fortunately, theywere never used as extensively as CFCs.

They were found to be so inert they did not react with the troposphere. They gradually diffuseinto the stratosphere where they react with UV light to form chlorine and, fluorine freeradicals.

Substance Formula Previous UseCFCs

Chloroformdichloromethane

CHCl3CH2Cl2

anaesthetic

Tetrachloromethane CCl4 Cleaning fluiddichlorodifluoromethane CCl2F2 propellantChlorofluoromethaneChlorotrifluoromethaneTrichlorofluromethanedichlorodifluoromethane

CH2ClFCClF3CCl3FCC2F2

refrigerant

Dichlorodiphenyltrichloroethane C14H9Cl5 insecticide

Identify and name examples of isomers (excluding geometrical and optical) ofhaloalkanes up to eight carbon atoms

Naming Simple halogensUse prefixes for the halogen group (i.e. Bromo, Chloro, Fluoro, Iodo)

Use prefixes for more than one of the same halogen (e.g. di, tri, tetra)

If more than one halogen atom is present, list them alphabetically by halogen name. E.g. C4H5BrCl2I2 is called “Bromodichlorodiiodobutane”.

Number the carbon atom with the halogen attached, giving preference to any double bond.Otherwise, give lowest number to the halogen group

Examples:a) 3,4-dibromo-1,2,5-trichloro-4-fluroheptane

b) 1,1,2,3-tetrachloropropane



c) 2,3-difluoro-4-iodopentane

d) Tetra chloromethane

Gather, process and present information from secondary sources includingsimulations, molecular model kits or pictorial representations to model isomers ofhaloalkanes

Example Isomer: BromoDichlorofluoropropane- C3H4BrCl2F (23 Isomers)

1-bromo-1, 1-dichloro-2-fluoropropane











H

H

H

Cl

Br

C C

H

F

C Cl

H

H

F

Cl

Br

C C

H

H

C Cl

H

H

Cl

Cl

Br

C C

H

F

C H

H

F

Cl

Cl

Br

C C

H

H

C H

H

C

Cl

Cl

Br

C C

H

H

C F

H

C

H

Cl

Br

C C

H

Cl

C F

H

C

H

Cl

Br

C C

F

Cl

C H

H

C

F

Cl

Br

C C

H

Cl

C H

H

H

H

F

Br

C C

Cl

Cl

C H

H

H

F

H

Br

C C

Cl

Cl

C H

H

H

Cl

F

Br

C C

Cl

H

C H















Present information from secondary sources to write the equations to show thereactions involving CFCs and ozone to demonstrate the removal of ozone from theatmosphere

CFCs undergo photodisassociation when exposed to UV radiation to form reactive chlorinefree radicals. For example:

H

H

Cl

H

Br

C C

Cl

F

C H

H

F

Cl

H

Br

C C

H

Cl

C H

H

Cl

Cl

F

Br

C C

H

H

C H

H

Cl

Cl

H

Br

C C

H

F

C H

F

Cl

Cl

H

Br

C C

H

H

C H

H

H

H

Cl

Cl

C C

H

Br

C F

H

H

H

Cl

Cl

C C

F

Br

C H

H

H

F

Cl

Cl

C C

H

Br

C H

F

H

Cl

H

H

C C

H

Br

C Cl

H

H

Cl

H

Cl

C C

F

Br

C H

H

F

Cl

H

F

C C

Cl

Br

C H

H

H

Cl

H

F

C C

Cl

Br

C H



The chlorine radicals then react with ozone to form the chlorine monoxide radical.

Further reaction by oxygen radicals regenerates the chlorine radical. It is acting as a catalystfor ozone decomposition.

By adding the two above reactions, we get the net equation:

Ozone has been converted into oxygen and oxygen radicals, which could have formed moreozone, have been ‘mopped up’.This process is more frequent in Winter and Spring due to more ice particles which provide asurface catalyst. Present information from secondary sources to identify alternative chemicals used to

replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs

Hydrochlorofluorocarbons (HCFCs) and hydrochlorocarbons (HFCs) are the two mainalternatives for CFCs.

HCFCs substitute some of the chlorine atoms with hydrogen. They are decomposed by OHfree radicals in the troposphere, however, this process is slow and they can still reach thestratosphere and form chlorine radicals.

HFCs contain no chlorine and are under being trialled. They react with OH more readily thanCFCs. Because they contain no chlorine, they produce no undesirable radicals in thestratosphere.

However, both HCFCs and HFCs are greenhouse gases with long atmospheric lives (due totheir stability).

Hydrocarbons have replaced CFCs as aerosol propellants and refrigerants in air conditioners.They do not affect the ozone, but they are flammable.

The main HCF used in Australia is 1,1,1,2-tetrafluoroethane:

Discuss the problems associated with the use of CFCs and assess the effectiveness ofsteps taken to alleviate these problems

Problems include:-Depletion of the ozone layer, leading to more UV reaching Earth, which increases risk ofsunburn, cancers, crop failure



-an enhanced greenhouse effect, contributing to global warming

Steps to alleviate problemsThe Montreal Protocol, a 1987 International agreement between many countries to eliminateCFC emissions. Further assistance has been given to developing countries to phases outCFCs. The effectiveness is dependant on government regulation of use and production ofCFCs.

CFCs were gradually replaced by similar chemicals such as HCFCs and HFCs. However, theyhave their own problems, namely that they are greenhouse gases with long atmospheric lives.The use of air pump mechanisms in aerosol cans has been more effective.

Although CFCs cannot be removed, the effects of high UV levels can be alleviated by usingnew sunscreens, as advised by organisation such as the Cancer council and use of UVstabilisers in polymers to reduce photodisassociation by UV.

Analyse information available that indicates changes in atmospheric changes inatmospheric ozone concentrations, describe the changes observed and explain howthis information was obtained

CFCs were first developed to replace ammonia in refrigerators, as many poisoning fatalitieshad occurred. CFCs were found to be very inert and non-toxic in the troposphere and theysoon became widely used. Measurements of ozone concentrations in the 1970’s indicatedCFCs were depleting the ozone in the stratosphere.

In the 70’s, Scientist in Holland investigated the effect of nitrous oxide on the atmosphere andfound the sources were from artificial fertiliser and aircraft exhausts. This led to increasedconcern over the stability of the ozone layer.

Further investigations showed CFCs to be ozone depleting and later tests showed that halonswere even more readily broken down by UV than CFCs, releasing bromine free radicals.

Regular measurements have been made since the 1920’s and more intensive measurementssince the 1970’s. A worldwide decline in stratospheric ozone layers of about 10% has beenrecorded. It has been found that a ‘hole’ develops over Antarctica each spring and the declineexceeds 50%

The concentration of ozone is measured using analysis devices sent up by balloons or using aDobson spectrophotometer which measures the intensity of different frequencies of UVradiation and compares it to a frequency which is not strongly absorbed by ozone. Similarinstruments can be sent up by satellites in orbit, which measure the amount of UV scatteredby the atmosphere to give ozone concentrations at different altitudes.

Even partial destruction can result in harmful UV exposure, leading to skin cancers, sunburnand disrupted plant growth, even leading to a worldwide food crisis.



5. Monitoring and Management in water

Identify that water quality can be determined by considering:-Concentrations of common ions-Total dissolved solids-Hardness-Turbidity-Acidity-Dissolved oxygen and biochemical oxygen demand

Concentrations of common ionsThe concentration of common ions e.g. Chloride and sulfate, can be determined bygravimetric analysis using precipitation reactions (e.g. adding silver ions to chloride andweighting the precipitate). AAS is used to determine concentrations of metal ions e.g.Sodium, aluminium, magnesium

Total dissolved solids (TDS)TDS are determined by evaporating a filtered sample of a known volume. Most dissolvedsolids are ions, so their presence can be determined using a data logger set to record electricalconductivity. The amount of TDS is converted to ppm and expressed as

HardnessHardness is due to the presence of Ca2+ and Mg2+. These react with soap molecules to forman insoluble precipitate resulting in poor lathering ability and blockage of water pipes. Hardness is tested by precipitating the Mg2+ or Ca2+ ions with sodium carbonate (Na2CO3)of a known concentration, followed by gravimetric analysis of the weighed solids.

TurbidityTurbidity is a measure of the ability of water to support life. It results from suspended solidsin the water, causing ‘cloudiness’ which prevents light penetration and therefore,photosynthesis which in turn reduces the oxygen concentration. It is tested by pouring asample into a turbidity tube until the cross at the base becomes invisible. However, theturbidity cannot be accurately measured, only compared.

Lowturbidity

Highturbidity



AciditySafe drinking water has a pH of ≈6.5 due to dissolved CO2. pH values ±2 units from neutralindicate polluted water. Water pH is tested using either universal indicator with colourcomparison chart or a pH probe.

Dissolved oxygen (DO)This measurement is important for safety of drinking water. Low O2 concentrations indicatestagnant water.

DO is measured using the Winkler test, which fixes the oxygen concentration for laterdetermination by titration. The amount of manganese dioxide produced by adding manganese(II) ions and hydroxide ions is a measure of the DO. Acidified Iodide ions are the added toproduce a yellow iodine solution. This is then titrated against a standard sodium thiosulphatesolution using a starch indicator. The indicator turns the solution blue, which disappears atthe endpoint.

The overall reaction is:

Therefore, 1 mole of dissolved oxygen produces 4 moles of thiosulphate (S2O32-)

Biochemical oxygen demand (BOD)BOD5 measures the amount of oxygen used by bacteria and microorganisms in a sealedcontainer. One sample is kept in the dark for 5 days, so no photosynthesis (and therefore nooxygen is produced) occurs while the other is tested immediately. The BOD is the differencebetween the initial and the final DO values and is given in mg/L. Although BOD givesprecise quantitative measurements, it is commonly used as an indicator of water quality.

Identify factors that affect the concentrations of a range of ions in solution innatural bodies of water such as rivers and oceans

Factors include:-rainfall frequency (e.g. floods and droughts)-water temperature-evaporation rates-soil/rock type-water pH-pathway of water (if it flows through ground aquifers the water will be ‘harder’)-presence of animal faeces

Human activitiesFarming practise such as removal of vegetation and irrigation increases salt concentration inrivers. Water flowing through fertilized land becomes contaminated with nitrate andphosphate ions. Mining exposes sulphides which are oxidised by the air, forming sulfuric



acid. Other human activities include sewage treatment run-off, heavy metals from factories,mines and storage dumps.

Describe and assess the effectiveness of methods used to purify and sanitise masswater supplies

There are several methods to purify water. Most are variations on the following process:

FlocculationWater is collected in dams and pumped to a treatment site where larger debris is removed viascreens. Fine particles normally have electric charges which prevents them from joining.Separation of fine particles involves adding coagulating agents such as Iron (III) chloride(FeCl3). This neutralises the surface charges so the particles join and also forms iron (III)hydroxide Fe(OH)3 precipitate. The particles ‘flocculate’ into a large mass which is easilyfiltered.

FiltrationThe water is passed through beds of sand and carbon. The sand traps the floc and the carbonabsorbs organic molecules which have unpleasant odours and tastes.

ChlorinationThe water is clear of any particles at this stage, but may contain dangerous microbes. Thereare several chemicals which may be added to sanitise the water:

-Chlorine gas (Cl2) at 2 ppm-sodium hypochlorite (NaClO(l)) at 1L/4000L-calcium hypochlorite Ca(OCl(s))2-Monochloramine (NH2Cl), less powerful but longer-lasting, is made by reacting ammonia(NH3) with chlorine (Cl2)

pH adjustmentWater is normally slightly acidic (pH≈6.5) due to dissolved CO2. The easiest way toneutralise water is by using forced draft degasifiers. Lime is commonly used at the start ofwater treatment, as it increases water hardness, facilitating flocculating and minimising therisk of heavy metals from pipe fittings dissolving into the water.



Assessment of effectivenessThis involves testing water samples for microbes throughout the entire purification andsanitisation process esp. during sanitisation. Also required are public health surveys andmedical reports of incidences of water-borne illnesses

In Australia, the incidence of health problems arsing from sub-standard water is nil in mostyears. However, in 1998 there was an outbreak of cryptosporidium and giardinia in NSW.Nowadays, water supplies are monitored daily at water treatment plants and catchment areas.This is considered highly effective and less costly than installing microscopic filters.

Describe the design and composition of microscopic filters and explain how theypurify contaminated water

Microscopic Membrane FiltersThese filters are able to filter out even microbes, avoiding the need to chemically treat thewater i.e. they filter out all small particles, including microbes. They can be classified asmicro-, ultra-, nano-filtration (as small as 1μm) or reverse osmosis.

The membrane is generally made into a film or a ‘capillary tube’. It is composed of polymers(e.g. polypropylene), which are dissolved in a mixture of solvents. Water-soluble powders areadded to form the pores. The mixture is spread on a plate or moulded into a tube for thesolvent to evaporate. Once the membrane solidifies, it is placed in water to produce themicroscopic pores.

Semi-permameable membranes for reverse osmosis are made of cellulose acetate, polyamideor composite films. Under pressure, these have high water permeability but block most otherions, molecules and atoms.

Although each pore is microscopic, the largenumber of pores creates a large surface areaDirty water is forced through the pores in thepipe under high pressure to speed up theprocess. For sheet filters, water is passedacross the membrane as this reducesblockage. For capillary tubes, water is passedthrough the pores into the tube under highpressure.

Compared to sand filters, membrane filtersare very expensive but also effective. Othercountries such as Singapore use membrane

filters to recycle sewage water for re-use. In Australia, they are mainly used for filteringhigh-quality bottled drinking water.

Perform a first-hand investigation to use qualitative and quantitative tests to analyseand compare the quality of water supplies

Fine particlestrapped on outsideof capillary tube

Clean waterpasses through



Gather, process and present information on the range and chemistry of the testsused to:

-identify heavy metal pollution of water-monitor possible eutrophication of waterways

Heavy metal pollutionHeavy metal pollution of water is caused by unacceptably high levels of ions of arsenic,cadmium, copper, lead, mercury, nickel and zinc. The most likely and dangerous of these arelead and mercury. Gravimetric analysis using precipitation reactions will not work, becausedangerous concentrations are too small to be detected. Instead, AAS or mass spectroscopy areused

EutrophicationEutrophication involves excessive nutrient content due to fertilisers in waterways. Fertilisescontaining nitrate and phosphorus ions cause excessive algae growth and oxygen depletionwhen they die and decay. When this occurs, the biochemical oxygen demand (BOD) is said tobe extreme. This oxygen depletion kills all other organisms in the waterway. Eutrophicationusually occurs when water flows through farmland or when sewage water is discharged intowaterways.

Spectrophotometry is one method to determine phosphate concentrations. It involves reactingthe water sample with the reagent ammonium molybdite [(NH4)2MoO4], then addingascorbic acid which turns the sample blue. The blueness of the solution is proportional to theamount of phosphate. A photometer is used to measure the amount of light passing throughthe solution to a detector.

OtherquantitativemethodsincludeAAS andBODtests.

Gather, process and present information on the features of local town water supplyin terms of :

-catchment area-possible sources of contamination in this catchment-chemical tests available to determine levels and

Light passesthrough

Photometermeasures intensity

of light



-Types of contaminants-Physical and chemical processes used to purify water-Chemical additives in the water and the reasons for the presence of these additives

Local water supply: Hunter Water Supply

Catchment AreaWater comes from three main catchments:Grahamstown Dam supplies 30-45% of water to is the lower Hunter and has an area of100km2. It is used for many other activities including agriculture, recreation, tourism,residential & urban developments. Water is routinely monitored for pathogens before itreaches the catchment area.

Chichester Dam supplies 40% of water and has an area of 197km2. It is bound from the Northand East by the Great Dividing Range. It is located near Barrington Tops National Park and istherefore pristine and largely unaffected by human activities. Environmental flow releasesinto the connecting Williams river sustain natural ecosystems along Chichester River.

Tomago and Anna Bat sandbeds contribute to surface supplies and provide backup in times ofdrought. Tomago sandbeds supplies the Tilligerry peninsular while Anna bay supplies theTomaree peninsula. Together, they cover an area of 275km2 along a 10-15km coastal strip.Porous sand means there is little surface run-off.

Sources of contaminationLand in these catchments used for a variety of other purposes: -residential

-Industry-Transport and construction-Agriculture-Mining-Recreation-Defence for activities

The groundwater supply can be contaminated due to residential septic tanks and past historyof sand mining in the area.

Types of contaminants and TestsContaminant Test

suspended fine particles (clay and silts)Suspended organic matter

Turbidity test using turbidity tube

manganese AAS, mass spectroscopyAcidic or basic compounds pH probe, universal indicator

Microorganisms (pathogens) BOD5, microscopic filters



Physical & Chemical Processes used to purify water and chemical additives

Screening: sieves remove larger solids e.g. twigs, fish, leaves

↓Coagulation/flocculation: Alum (hydrated potassium aluminium sulfate, KAl[SO4]2·H2O)

or a polymer is added to the water to make small particles clump together, forming aneasy-to-remove ‘floc’.

↓Sedimentation: The floc and water flow into sedimentation basins, the ‘floc’ settles as

sludge at the bottom.

↓Filtration: Water flows through sandbeds to remove suspended matter. Sandbed filters are

routinely cleaned by backwashing.

↓Disinfection: Chlorine (Cl2) is added to kill any pathogens

↓Sludge drying: ‘Floc’ sludge is piped to drying lagoons

↓Fluoridation: Fluoride is added to reduce dental caries

↓pH adjustment: lime [Ca(OH)2] is added to stabilise pH (esp. ‘soft’ water) and prevent

corrosion of pipelines

module 3 chemical monitoring and management

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