Ms. Faulder
Chemistry Assessment Task 3
1. RUBBER IS A NATURAL PRODUCT THAT IS NOT A FOSSIL FUEL. DESCRIBE THE ISSUES
ASSOCIATED WITH THIS SHRINKING WORLD RESOURCE UNDER THE FOLLOWING
HEADINGS:
USES OF RUBBER AND THE PROPERTIES THAT MAKE IT USEFUL
USES:
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Rubber is made in many articles including:
o Raincoats
o Electrical insulation
o Erasers
o The most important use for rubber is for tyres.
 Most tyres contain several types of rubber that are both natural and synthetic.
PROPERTIES:
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Rubber has many properties that make it useful:
o Elastic
 The molecules that make up rubber are long, coiled and twisted. They are elongated
when stretched but resumes to its original shape when force is removed.
o Waterproof
o Good insulator against electricity
o Natural rubber is resistant to tearing and heat
o Other properties are present in rubber depending on the type of rubber include:
 Resistant to:
 Oils
 Solvent
 Other chemicals
Vulcanisation is used to increase rubber’s:
o Resistance to heat, cold, abrasion and oxidation
o Airtight and resistant to deterioration by sunlight
o Improves elasticity
CHANGE IN ITS USE OVER TIME
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Rubber was initially used as eraser
Rubber was also used in waterproof boots - but melted when left in the sun for too long
In 1842, rubber was vulcanised for the first time
In 1850, rubber toys were being made
In 1830, bicycles had tyres made out of rubber but it wasn't commonly so until later.
In 1895, rubber was being made into tyres for cars and since then it had a large global market.
During World War 2, the mass production of rubber was required for the US to supply its jeeps, tanks and
other vehicles with tyres for the war initiative.
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By: Raymond Chen
Ms. Faulder
Chemistry Assessment Task 3
SOURCES OF RUBBER
NATURAL SOURCES
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Rubber is obtained from a variety of plants, but the majority of the natural rubber comes from the rubber
tree, Hevea Brasilliensis.
Grown in the Amazon Basin as well as other tropical areas.
Other sources of rubber include the guayule plant, the gutta-percha tree and the Russian dandelion.
SYNTHETIC SOURCES
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There are four main types of synthetic rubber:
o Styrene-butadiene rubber – SBR:
 Produced from two monomers – butadiene and styrene
 Butadiene is obtained from petroleum, butane or ethyl alcohol
 Styrene is obtained from petroleum or benzene
 These monomers are made into SBR by the emulsion polymerisation process.
 The monomers are made with water and soap to from an emulsion and with a catalyst to
begin the process along with other substances undertaken at around 4°C.
 Durable and resistant to abrasion, heat and cold.
 It is used in mainly tyres, shock absorbers, gaskets, hoses and adhesives.
o Polybutadiene Rubber:
 Produced from butadiene by the solvent polymerisation process.
 Monomer is dissolved in a hydrocarbon solvent and polymerised at 49°C – catalyst is
alkylaluminium.
 Closely resembles natural rubber – it is highly elastic and resistant to abrasion, heat and
cold – normally blended with SBR.
o Butyl Rubber:
 Produced from isobutylene and isoprene – obtained from petroleum.
 Monomers are dissolved in a chlorinated solvent and polymerised at about -101°C –
catalyst is aluminium chloride.
 Resistant to acids, oxygen and heat and used in electrical insulation, hoses and adhesives.
PROBLEMS ASSOCIATED WITH THE USE OF RUBBER
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Trees are getting cut down in the Amazon so that rubber trees can be planted
Emissions of sulfur dioxide into the air causes dangerous pollution
Accelerators and anti-detergents release hydrocarbons into the air
Zinc oxide catalyst used in vulcanisation is toxic to aquatic organism
CO2 emissions from production is also a major source of pollution
WHAT IS BEING DONE ABOUT THE PROBLEMS
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Synthetically produced by companies through emulsion polymerisation.
Vulcanised with sulfur and white lead
EVALUATION OF THE PROGRESS BEING MADE TO SOLVE THE PROBLEMS
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These solutions have been successful in increasing the supply of rubber
They are also able to make the rubber stronger, more elastic, cheaper and perform better in harsh
conditions
2
By: Raymond Chen
Ms. Faulder
Chemistry Assessment Task 3
OUTLINE THE POSSIBLE CAUSES OF THE SHRINKAGE OF WORLD SOURCES OF RUBBER.
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Causes of shrinkage of world rubber include:
o Deforestation - cutting down of trees in the Amazon reduces the number of rubber trees
o High demand, hence shrinkage in world sources
o Takes too long to harvest
IDENTIFY THE REPLACEMENT MATERIALS WHICH HAVE BEEN DEVELOPED TO TAKE THE PLACE OF
RUBBER.
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Styrene butadiene rubber
2. OUTLINE THREE USES OF SULFURIC ACID.
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Sulfuric acid is the most commonly produced chemical in the world. Some of the major uses of sulfuric
acid include:
Fertiliser – used to make superphosphate fertiliser. Rock phosphate Ca2(PO4)2 is reacted with sulfuric acid
forming calcium dihydrogen phosphate which is soluble in calcium sulphate which is then sold as
superphosphate. Phosphate of ammonia is made from ammonia and sulfuric acid.
Hydrating/Dehydrating Agent – used to add or remove H2O from ethylene or ethanol, respectively.
Lead-acid batteries for motor cars – used in the electrolyte of the batteries.
3. DESCRIBE THE FRASCH PROCESSES USED TO EXTRACT SULFUR FROM MINERAL DEPOSITS.
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Deposits of elemental sulfur are extracted from these deposits by a process known as the Frasch
Process.
o Water is superheated – heated under
pressure – to 160°C.
o It is then forced down the outer of three
concentric pipes into the sulfur deposit.
o This melts the sulfur – melting point 113°C –
and forms an emulsion – small droplets of
one liquid dispersed through another liquid.
o Compressed air is blown down the inner
pipe and this forces the water-sulfur
emulsion up the middle pipe.
o The mixture cools, the coiled sulfur
separates from the liquid water and 99.5% of
sulfur is obtained.
4. IDENTIFY THE PROPERTIES OF SULFUR WHICH ALLOW ITS EXTRACTION
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Low melting point of 113°C due to weak dispersion forces between its molecules – superheated
pressurised water at 160°C can readily melt sulfur.
Insoluble in water and doesn’t react chemically hence easy for separation.
Low density produces an emulsion that is light and easily transportable.
It is inert, non-toxic and non-volatile.
3
By: Raymond Chen
Ms. Faulder
Chemistry Assessment Task 3
5. ANALYSE POTENTIAL ENVIRONMENTAL ISSUES THAT MAY BE ASSOCIATED WITH IT
EXTRACTION
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Recovered water must be cooled to avoid thermal pollution and needs to be recycled to avoid
contamination.
Sulfur is cooled quickly to avoid oxidisation and production of sulfur dioxide – it can also produce
hydrogen sulfide which is also poisonous.
Once extracted the mines can be susceptible to ground subsidence.
6. OUTLINE THE STEPS AND CONDITIONS NECESSARY FOR THE INDUSTRIAL PRODUCTION OF
H2SO4
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The Contact Process is the main method of producing sulfuric acid from elemental sulfur.
It has four stages:
o Sulfur combusts to form sulfur dioxide.
 Elemental sulfur is melted and sprayed under pressure into an excess of dry air in the
combustion chamber of the sulfur furnace.
 The sulfur reacts with the oxygen molecules in the air forming sulfur dioxide
 Done in temperatures of about 1000°C which is then cooled to 400°C.
o Catalytically converted into sulfur trioxide
 Vanadium oxide (V2O5) on a silica pellet catalyst is used.
 400-550°C at 100-200kPa.
 Normal air is used as higher pressure will push the equilibrium to the right.
o Sulfur trioxide is dissolved in previously manufactured sulfuric acid to form oleum.
o Oleum reacts with water to form sulfuric acid.
7. DESCRIBE THE STEPS AND CONDITIONS NECESSARY FOR THE PRODUCTION OF SO 3 FROM
SO 2 , INCLUDE EQUATIONS
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The equation for the conversion is:
2𝑆𝑂2(𝑔) + 𝑂2 ⇌ 2𝑆𝑂3(𝑔) ∆ = −99𝑘𝐽/𝑚𝑜𝑙
CONDITIONS
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Like in ammonia compromise conditions must be made between high yield and high rate.
The reaction mixture is passed over a catalyst bed at about 550°C - roughly 70% of the SO2 is oxidised.
The reaction mixture is then cooled to 400°C and then passed over the vanadium oxide catalyst - slower
but 97% yield
The rest is run over the catalyst again - yield reaches 99.7%
The conditions required to push the equilibrium to the right is to:
o A pressure of a little above normal atmospheric pressure - 100kPa
o Small excess of oxygen
o Vanadium oxide supported on silica catalyst
o Temperature of catalyst beds of 550°C - high rate - or 400°C - high conversion
o 99.7% conversion yield
4
By: Raymond Chen
Ms. Faulder
8.
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Chemistry Assessment Task 3
APPLY THE RELATIONSHIP BETWEEN RATES OF REACTION AND EQUILIBRIUM CONDITIONS
TO THE PRODUCTION OF SO 2 TO SO 3
The overall equation of the conversion of SO2 to SO3 is an equilibrium one:
2𝑆𝑂2(𝑔) + 𝑂2(𝑔) ⇌ 𝑆𝑂3(𝑔) ΔH = − 99kJ/mol
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According to L.C.P. increasing the pressure will increase the product produced.
According to L.C.P. decreasing the temperature will increase the product produced.
To increase product produced:
o Excess of oxygen
o Higher pressure
o Lower temperature
o As with ammonia, to increase the rate of the reaction of converting SO2to SO3 is to use a catalyst.
o The catalyst used is vanadium oxide (V2O5) supported on porous silica pellets.
o It produces a high reaction rate at above 500°C and not too slow at 400°C.
9. ANALYSE THE PROCESS TO PREDICT WAYS IN WHICH THE OUTPUT OF SULFURIC ACID CAN
BE MAXIMISED BY DRAWING A FLOW CHART AND WRITING APPROPRIATE EQUATIONS
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A compromise is taken to ensure maximum efficiency.
Pressure is kept constant at about 100kPa
Reaction mixture is passed over the catalyst at about 550°C – 70% is oxidised quickly
Reaction then cooled to 400°C – reaction is slowed but yield is at 97%.
Remaining SO2 is passed over another bed of catalysts – results in 99.7% efficiency
Modern plants arrange to use some of the heat released during the process to melt the sulfur and use
the rest to form steam for electricity generation – hence large amounts of energy can be saved – cost
effective and reduced environmental damage.
Sulfur to Sulfur Dioxide
𝑆(𝑙) + 𝑂2(𝑔) → 𝑆𝑂2(𝑔)
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Sulfur Dioxide to Sulfur
Trioxide
2𝑆𝑂2(𝑔) + 𝑂2(𝑔) → 𝑆𝑂3(𝑔)
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Sulfur Trioxide to Oleum
𝑆𝑂3(𝑔) + 𝐻2 𝑆𝑂4(𝑙) → 𝐻2 𝑆2 𝑂7(𝑙)
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Oleum to Sulfuric Acid
𝐻2 𝑆2 𝑂7(𝑙) + 𝐻2 𝑂(𝑙) → 2𝐻2 𝑆𝑂4(𝑙)
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By: Raymond Chen