Download HSC Chem Production of Materials

Chemistry
Production of Materials
1. Fossil fuels provide both energy and raw materials such as ethylene for the
production of other substances.
 Construct word and balanced formulae equations of chemicals reactions as they
are encountered.
Word equation – Hydrogen + Oxygen  Water
Balanced chemical equation - 2H2(g)+O2(g)2H2O(g)

Identify the industrial sources of ethylene from the cracking of the fractions from
the refining of crude oil.
Ethylene can be obtained from the fractional distilling of crude oil and natural gas.
However this is not enough to meet the demand of the petrochemical industry. Therefore
ethane is obtained by the cracking of larger hydrocarbon chains.
Cracking – the process where high molecular weight fractions of crude oil are broken in
to lower molecular weight substances in order to increased the output of high demand
products.
Catalytic cracking
This utilizes a zeolite( an aluminosilicate crystalline compound) . The reaction is carried
out without the presence of air at temperatures of 500oc. The zeolite acts as a surface on
which the reaction takes place. Zeolites absorb the hydrocarbon chains into their inner
surface. Zeolites are affective catalysts due to their large surface are per unit mass as they
have tunnels and cavities within the molecules. Catalytic cracking is insufficient to
produce the ethane demanded by the petrochemical industry.
Steam cracking
Steam cracking is the major source of ethane. Alkanes and steam are passed through hot
metal coils at 800 oc causing the alkanes to decompose completely into small alkenes
such as ethene, propene and butene.

Identify that ethylene because of the high reactivity of its double bond, can be
transformed into many useful products.
As an alkene ethane possesses an unsaturated double bond which can change into a single
bond giving each carbon at the end of the double bond extra bonding capacity. This
allows ethane to combine with a variety of molecules/atoms forming useful chemicals.
Products of these reactions include ethanol, pharmaceuticals and insecticides. It can also
form various monomers such as styrene for plastics.
Addition reaction – a chemical change where two new atoms/molecules are added across
the double bond; one on each carbon at the end of the double bond. This converts the
double bond into a single bond
- Hydrogenation – the addition of hydrogen to form an alkane.
C2H4(g) + H2(g)  C2H6(g)
Heating the reactants in the presence of a nickel catalyst.
- Halogenation – the addition of halogens
Used to distinguish between saturated and unsaturated hydrocarbons.
C2H4(g) + Cl2(g)CH2Cl(g) –CH2Cl(g)
Ethane + chlorine  1,2 dichloroethane
Using an iron(III) chloride catalyst.
- Hydrohalogenation – addition of hydrogen halides
CH2=CH2(g) + HCl(g)  CH3-CH2Cl(l)
Ethylene + hydrogen chloride  chloroethane
- Hydration – the addition of water to form ethanol
C2H4 (g) + H2O(l)  CH3-CH2OH(l)
Ethylene + water  ethanol
This is done in the presences of a sulphuric acid catalyst
Ethanol can be used as a disinfectant, anti freeze, drink, industrial solvent and alternate
fuel source.
 Identify ethene as a monomer from which polymers are made
Polymerisation – the process where identical small molecules combine together to form
one large molecule. The reactants are known as monomers and the product is a polymer.
Ethene is a monomer to the polymer polyethylene. It also undergoes substitution
reactions with chlorine to form chloroethene which is used as a monomer for PVC. It can
also be used to produce the monomer phenylethene from which polystyrene is made.
.

Identify polyethylene as an addition polymer and explain the meaning of the term.
Polyethylene is a polymer produced by the addition polymerisation of the monomer
ethene. It has the structural formula (- CH2-CH2-)n.
Addition polymerisation – the process where identical small molecules are joined
together in long chains in a way which all the atoms in the monomers are present in the
polymer. i.e. there is no addition product. This involves unsaturated monomers with a c=c
double bond joining together.

Outline the steps in the production of polyethylene as an example of a
commercially and industrially important polymer.
1.
2.
3.
4.
Extract crude oil
refine crude oil
fractionally distil crude oil and extract faction of ethene
Crack long chain hydrocarbon in order to obtain more ethene
Low density polyethylene
Ethene gas is heated up to high temperatures of 300oc and subjected to high pressure of
1000 to 3000 atmospheres. A peroxide initiator is then added to start the propagation of
the reaction. This initiator is not a catalyst as it is absorbed into the polymer chain at 1
every 2000 to 3000 monomer units. The peroxide initiator splits at the O-O bond forming
a free radical which attacks the double bond of an ethene molecule. The resulting
molecule R-O-CH2CH2, itself a radical attacks the double bonds of other ethene
molecules resulting in the addition of a –CH2-CH2- group. As the chains grow they curl
back resulting in the radical removing a hydrogen atom from a CH2 group within the
chain. This process of back biting causes branching. The reaction is terminated when two
radicals meet together or a terminating agent is added. The resulting product has many
branched chains which hinder the polymer molecules from stacking close together
resulting in a soft flexible low density plastic with a low melting point.
High Density Polyethylene
-Ethene is heatet to a temperature of 60oc at just a few atmospheres in the pressemce of a
Ziegler-Natta catalyst. This catalyst which is a mixture of titanium(III) chloride and a
trialkylaluminium compound forms unbranched polyethylene molecules which pack
together in an orderly fashion. The catalyst acts as a surface on which the reaction
happens. HDPE is more crystalline the LDHPE and harder but more brittle with a higher
melting point.

Identify the following as commercially significant monomers
- vinyl chloride
CH2=CHCl also known as chloroethene. It undergoes addition polymerization to form
poly(vinyl chloride) also known as PVC.
- styrene
CH2=CHC6H6 also known as phenylethene. It undergoes addition polymerization to
form polyphenylethene or Polystyrene as it is more commonly known.
Structure
CH2=CHCl
Common
Name
Vinyl chloride
Systematic
Name
chloroethene
CH2=CHC6H6
Styrene
phenylethene

Common
Polymer Name
Poly(vinyl
chloride)
polystyrene
Systematic
Polymer Name
Poly(chloroethene)
Poly(phenylethene)
Describe the use of polymers made from above monomers in terms of their
properties.
LDPE is soft, flexible, low density, translucent, thermoplastics and impermeable to water
allowing it to be used as films such as cling wrap, plastic containers, plastic bags and
garbage bag. It is also an electrical insulator allowing it to be used as wire insulation.
HDPE is hard to semi flexible, high density, transparent/translucent and impermeable to
water. This allows it t be used in pipes that carry natural gas, containers to hold oils,
petrol, detergents and acids, children’s toys, plastic buckets, lunch boxes and playground
equipment. It is also an electrical insulator allowing it to be used as wire insulation.
PVC is not particularly useful as it is hard, brittle and tends to decompose upon heating.
However additives can be added to extend its flexibility and stability making it more
useful the LDPE or HDPE. Rigid PVC is used in external cladding, guttering and down
pipes, electrical conduit, waste water pipes, rigid panels and floor tiles. Kitchen utensils
and credit cards are also made out of PVC. Flexible PVC is used in upholstery coverings
for cars and furnishings, electrical insulation and gardening hoses. PVC is impervious to
oils and other organic compounds and is used to make bottles that hold these materials.
PVC is used to protect surfaces, transport and hold liquids because of its water fast nature.
Styrofoam is produced by blowing gas through liquid polystyrene until it froths to foam
which is then allowed to solidify. The gasses trapped within Styrofoam are an excellent
lightweight insulator. Styrofoam is used in cups, eskies, fast food containers and packing
material. Styene can also be produced as a hard clear brittle plastic. It is clear as few
crystals are formed within it and the benzene ring in its structure makes it more stiff..
This clear plastic is used to manufacture cassette and CD cases, clear plastic drinking
cups Polystyrene is good for making cases as it is impact resistant and unreactive. By
adding coloring and other additives styrene can also be made in computer and television
cabinets, wall tiles and sturdy furniture.

Gather and present information from first hand or secondary sources to write
equations to represent all chemical reactions encountered in the HSC course.

Identify data, plan and perform first hand investigations to compare the
reactivities of appropriate alkenes with the corresponding alkanes in bromine
water.
Saturated hydrocarbons do not react with bromine water. Unsaturated hydrocarbons
undergo an addition reaction with bromine water causing the bromine water to lose its
colour as the bromine reacts with the alkene.

Analyse information from secondary sources such as computer simulations and
molecular model kits or multimedia resources o model the polymerisation process.
2. Some scientists research the extraction of materials from biomass to reduce our
dependence on fossil fuels.

Discuss the need for alternative sources of the compounds presently obtained by
the petrochemical industry.
Petrochemicals are chemicals derived from the factions of petroleum. Petroleum is a
finite resource with Australia’s petroleum reserve to diminish in 35 years and our natural
gas reserves to be diminished in125 years. Fossil fuels are finite as the take millions of
years to form. The main use of these resources, 95%, is combustion for energy. To meet
demand in the future alternative sources must be found. These can be petroleum products
made from biomass such as biopolymers for plastics and ethanol for fuel. As petroleum
supply diminishes it will cause prices to rise having adverse affects on the world
economy also an alternate renewable fuel source is needed to meet energy needs in the
future and reduce carbon emissions which is contributing to the enhanced greenhouse
affect.
 Explain what is meant by a condensation polymer.
Condensation polymers are long chains formed by joining monomer units with the
elimination of water or other small molecule when a pair of monomers join together.

Describe the reaction involved when a condensation polymer is formed.
Condensation polymerisation – the process where two functional groups of two
molecules come together with the elimination of water or small molecule causing the two
functional groups to be linked together.
E.g cellulose
HO-C6H10O4-OH HO-C6H10O4-OH HO-C6H10O4-OH
Becomes
-O-C6H10O4-O-C6H10O4-O-C6H10O4- + xH2O
alternatively it can be written
n(HO-C6H10O4-OH)H-( O-C6H10O4)n-OH + (n-1)H2O

Describe the structure of cellulose and identify is as an example of a condensation
polymer found as a major component of biomass
Cellulose is a polymer made from the monomer glucose. Glucose has the structural
formula HO-C6H10O4-OH. It has 5 carbon atoms and 1 oxygen atom in a puckered ring
with oh groups on 5 of the carbon atoms. The c-c bond is shown on the top or the bottom.
When glucose is combined with cellulose the OH on the right hand C atom of one
molecule combines with the OH of the left hand carbon atom of the next glucose
molecule. Forming the -O-C6H10O4-O-C6H10O4- chain. Each alternate glucose molecule
in the chain is inverted. This produces a very linear molecule caused by the c-o-c bonds.
This is a condensation polymerisation as water is eliminated from the chain as an OH is
taken from one molecule and a H from another. There are strong hydrogen bonds
between lines of cellulose molecules giving it strength and rigidity. As the hydroxyl
groups within cellulose are involved in hydrogen bonding between other cellulose
molecules cellulose is not soluble in water.
Cellulose is the major component of plant and animal material known as biomass
Biomass refers to the materials produced by living organisms.

Identify that cellulose contains the basic carbon-chain structures needed to build
petrochemicals and discuss its potential as a raw material.
Each glucose unit of cellulose has four carbon atoms joined together in a chain. Therefore
it could be regarded as the basic structure of making the starting molecules for
petrochemicals as most polymers are made from 3 carbon chain monomers. The carbon
chains in cellulose can be changed into the chains present in petrochemicals if a microorganism can be developed or found to decompose cellulose into glucose and then from
glucose to 3or 4 carbon chains. However this process must not require excessive amounts
of energy and is able to meet world demand. Cellulose has high potential as a raw
material if this process can be found as cellulose is a renewable resource and replace our
dependence on a finite supply of petrochemicals.
Cellulose is currently used to make polymers such as rayon and cellophane. It can also be
used as an alternative fuel through fermentation of glucose. Ethanol can be dehydrated to
form ethene and thus replace our reliance on ethane obtained from fossil fuels to make
plastics and other chemicals. This process however requires vast amounts of electricity
which is fuelled by fossil fuels offsetting the gain. Thus in order for it to become viable
technology must improve to make the process more energy efficient.

Use available evidence to gather and present data from secondary sources
and analyse the properties in the recent developments and use of a named
biopolymer. This analysis should name a specific enzyme or organism used to
synthesise the material and an evaluation of the use of potential uses of the
polymer used based on their properties.
Poly (hydroxyalkanoates) or PHAs are a group of biopolymers produced from glucose
using a bacterial catalyst. The property of the polymer produced depends on the bacterial
strain and the conditions under which the fermentation process takes place. The polymers
can be either thermoplastics or elastomeric plastics. These polymers are originally used
by the bacteria for energy storage but have been found to have potential to replace the oil
based thermoplastics. PHA’s are more desirable than thermal plastics as they are
renewable resources and do not have the same disposable problems as thermo plastics
due to their ability to biodegrade.
The first PHA to reach the market was Polyhydroxybutyrate or PHD. It is synthesised by
using the microbes Alcaligenes eutrophus or Bacillus megaterium. The bacteria are fed
on glucose and can create polymers of up to 80% of their dried weight. These bacteria
have undergone genetic modification in order to increase the yield of polymer. This has
resulted in the price of production falling from $800 a pound in 1980’s to <$1a pound
today. The glucose used is usually wastes from places such as sugar mills and milk
processing. By controlling the carbon sources of the bacteria changes the properties of the
given polymer. Originally the first PHB produced was too brittle to be of much use.
However it was discovered that when propionic acid was added to the bacteria’s diet a
new polymer was produced which was far more flexible. Polyhydroxybutyratehydroxyvalerate or P (HB-HV) is formed with the use of Alcaligenes eutrophus and is fed
precise proportions of glucose and propionic acid. The structure of this new polymer has
Hydroxybutyrate and hydroxyvalerate molecules alternating in the chain at random. By
making the polymer more flexible it has expanded the available uses of this polymer.
PHA’s are marketed under the name Biopol. These polymers have an elasticity of 5%
to >10000% elongation at break, UV stability, water stable yet biodegradable in marine,
soil, compost and waste treatment environments, excellent film forming properties from
aqueous latex and environmentally compatible. PHA’s can be used as polymer
performance enhancers, non-woven fabrics, film and fibre, adhesives and coatings,
binders for metals, biodegradable packaging and water resistant coatings.
They are increasingly popular due to two major characteristics that they posses. PHA’s
are both biocompatible and biodegradable. Due to this biocompatibility they can be used
in medical application such as capsules for controlled drug release, surgical sutures, bone
plates and wound are without the fear of a reaction from the patient or the polymer being
toxic. They have the potential to be used a structural materials in personal hygiene
products and packaging applications. Although the cost of PHBV has fallen it is still far
more expensive than normal petroleum based polymers. The fact that PHA’s are
biodegradable makes them perfect for disposable packaging. It is currently used in
cosmetic containers and commercial films and paper coatings. There is also researching
to creating a biodegradable fishing net which will lead to decreased instances where sea
creatures are caught in disposed
3. oxidation-reduction reactions are increasingly important as a source of energy.

Explain the displacement of metal from solution in terms of a transfer of electrons.
When a more reactive metal is places in a solution of a less reactive metal salt. The less
reactive metal is displaced from the solution by the more reactive metals ions. Thus the
less reactive metal is seen deposited on the surface of the more reactive metal. We see in
the solution that the more reactive metal changes from a stable state into an ion in the
solution. The less reactive metal ion that was originally in the solution becomes a neutral
atom on the surface of the other metal. This is due to a transfer of electrons between the
two metal atoms. The more reactive metal donates electrons to the less reactive ion. The
atom of the more reactive metal becomes an ion and the ion of the less reactive metal
becomes an element. The non metallic ion in the salt solution is a spectator ion as it does
not participate in the reaction. The more reactive metal is oxidised and the less reactive
metal reduced. The reaction occurs due to the fact that the less reactive metal has a
greater tendency to gain electrons than the more reactive metal.

Identify the relationship between the displacement of metal ions in a solution by
other metals to the reactivity series.
-
The more reactive metal will change from an element to an ion
The less reactive metal will change from an ion to a neutral atom.
If a less reactive metal is placed in a solution of a more reactive metal no reaction will
occur as the more reactive metal atoms are already ions.
An activity series can be devised from these displacement reactions. Where the more
readily a metal is oxidised the more reactive it is. A more reactive metal has a greater
tendency to lose electrons and thus in a solution is oxidised while the less reactive metal
ion gains an electron forming a neutral state.

Account for changes in the oxidation state of species in terms of their loss or gain
f electrons.
Oxidation state – the number of electrons transferred to and from the neutral atom in
order to get to that state.
Oxidation – the loss of electrons is a increase in oxidation number. It can also be a gain in
oxygen loss of hydrogen.
Reduction – the gaining of electron is a decrease in oxidation number. Gain of hydrogen
loss of oxygen.
A neutral atom has an oxidation state of 0
A compound has an oxidation state of 0. The sum of the oxidation states of the atoms in it
is 0.

And

Describe and explain galvanic cells in terms of oxidation/reduction reactions.
Outline the construction of galvanic cells and trace the direction of electron flow.
Galvanic cells consists of two half cells which contain an electrode immersed in an
electrolyte solution. The electrolyte solutions are joined by a salt bridge which allows
negative ions to migrate from one of the half cells to the other in order to neutralise the
unbalance in charge. The electrodes are connected by an external wire to complete the
circuit.
In one half cell oxidation occurs while in another reduction occurs. As reduction occurs
at the cathode electrons are transferred from the cathode to the ions in the solution. At the
same time oxidation occurs at the anode causing electrons from the anode to be taken
away causing atoms to become ions. When the circuit is completed, by adding a salt
bridge and a wire between the electrodes, electrons flow through the circuit.
Oxidation occurs at the anode where electrons are produced from neutral metal atoms
forming ions. The anode is negative.
Reduction occurs at the cathode where electrons are accepted. Positive ions from the
solution accept electrons forming neutral atoms. The cathode is positive.
Salt Bridge allows the migration of ions in order to rectify an imbalance of charge. The
positive ions created from the anode migrate into the salt bridge while negative ions in
the salt bridge move to the oxidation cell. The excess of negatively charged ions in the
reduction cell is rectified by positively charged ions from the salt bridge moving to the
reduction cell and the negatively charged ions from the reduction cell moving into the salt
bridge. A porous pot can be used to balance charge allowing ions to move between cells
rectifying charge imbalances.
Daniel cell: zinc- copper cell
One half cell contains zinc anode immersed in zinc sulphate. The other half cell contains
the copper cathode immersed with copper sulphate. The are connected by a salt bridge.
Anode| electrolyte: salt bridge: electrolyte| cathode.
Zn|Zn2+(aq)
||
Cu2+|(aq)Cu
Oxidation half reaction
Zn(s) Zn2+(aq) + 2eReduction Half reaction
Cu2+(aq) + 2e-  Cu(s)
Salt bridge – Filter paper containing KNO3
Movement of electrons
The Zinc oxidises releasing electrons theses electrons move through the wire connected
the two electrodes. These electrons when at the cathode reduce the copper ions forming
solid copper. This however causes an imbalance in charge within each half cell. As
positive ions are created in excess at the anode and positive ions are taken away at the
cathode. Therefore electrical neutrality is maintained by positive ions migrating to the
cathode and negative ions migrating to the anode through the salt bridge.
Zn2+ moves from anode to cathode while NO2- moves from the salt bridge to the
oxidation cell. SO4- moves from the reduction cell to the salt bridge while K+ moves from
salt bridge to reduction cell.
Cell diagram
Single vertical line denotes a boundary between phases. The double vertical line donates
a salt bridge through which ions can move.



Pt, H2(g) | H+ || Au3+ | Au
o Anode is hydrogen gas bubbling over platinum electrode, in H+ solution.
Cathode is gold electrode dipping into Au3+ solution
Pt, H2(g) | H+, Cl- | Cl2(g), Pt
o Cathode is hydrogen gas bubbling over platinum electrode. Anode is
chlorine gas bubbling over platinum electrode. Both electrodes share a
common HCl(aq) electrolyte. There is no double line || because there is no
salt bridge.
Pt | I2, I- || Fe3+, Fe2+ | Pt
o Cathode is platinum electrode dipping into solution of iodine and iodide
ions. Anode is platinum electrode dipping into solution of Fe3+ and Fe2+
ions. There is no single vertical line | between Fe3+ and Fe2+ because they
are in the same phase. Rather, the boundary between phases is between the
platinum electrode, and the solution of both iron ions.
Function of a cell bridge
- complete the circuit
- Allow the migration of ions in order to maintain a balance of charge.
If one reactant is going from element to ionic form while the other is going from ionic to
elemental two separate half cells are needed. This is because if they shared a common
electrolyte the stronger reductant would automatically displace the weaker reductant.
A common electrolyte solution can be used if both reactants are going from an elemental
state to an ionic state as the reactants can’t react directly as they are physically separate.

Define the Terms anode, cathode, , electrode and electrolyte to describe galvanic
cells.
Anode: the electrode at which oxidation occurs. It has a negative charge.
Cathode: The electrode at which reduction occurs. It has a positive charge.
Electrode: electrical conductors in contact with the electrolyte solution and connected to
each other externally. They are an interface where oxidation and reduction occur.
Electrolyte: a substance which in a solution or molten conducts electricity; any substance
that contains mobile ions which behaves as an electrically conductive medium.

Perform a first hand investigation to identify the conditions under which a
galvanic cell is produced.
 Perform a first hand investigation and gather first had information to measure the
difference in potential of different combinations of materials in an electrolyte
solution.
 Gather and present information on the structure and chemistry of a dry cell or
lead-acid cell and evaluate it in comparison to one of the following:
- button cell
- fuel cell
- vanadium redox cell
- lithium cell
- liquid junction photovoltaic device
In terms of
- chemistry
- cost and practicality
- impact on society
- environmental impact
In terms of:
chemistry
Cost and
Practicality
Lead Acid cell
Porous lead anode and compressed
insoluble lead(IV) oxide cathode
submerged in dilute H2SO4
Anode oxidation:
Pb(s) + SO42-(aq) PbSO4(s) +2eE = +0.356V
Cathode reduction
PBO2(s) + 4H3O+(aq) + SO42-(aq)+2e-
PbSO4(s)+6H2O(l)
E = +1.685V
Net Process created +2.041V
Fuel Cells
Hydrogen diffuses into a carbon,
nickel or platinum anode while
oxygen diffuses into the cathode.
The electrodes act as catalysts for
a reaction with either an acidic or
alkaline electrolyte.
Acidic:
Anode oxidation
H2(g)2H+(aq) + 2eCathode Reduction
O2(g)+4H+(aq)+4e- 2H2O(l)
Alkaline electrolyte
Anode Oxidation
H2(g) +2OH-(aq) 2H2O(l) +2eCathode reduction
O2(g)+ 2H2O(l)+4e-4 OH-(aq)
Theoretical e.m.f is 1.23v but this
is difficult to obtain
Lead cells are relatively heavy and produce The fact that the H+ or OH-ions
relatively low power to their mass. The
must migrate through the
produce a relatively constant 2v and a large electrolyte solution to the
initial current which can be used to start a
respective electrode is a limiting
car. Lead cells can be recharged by
factor. Fuel cells have a large fuel
reversing the current flow. Lead batteries
efficiency for mass and produce
are the cheapest battery that can be
water as a bi-product however fuel
produced for what they do. Lead sulphate
cells are expensive to produce.
is deposited on the electrodes during use
Impact on
Society
this reduced the surface area of the
electrode reducing the rate of reaction and
eventually halting it. However this is
dissipated when a current flows in the
reverse direction. Lead Batteries last a
maximum of 3 hours before they need
recharging.
. However Lead batteries are the only
reliable source of energy that is cheap and
able to generate the large initial current
needed to start a car motor. This has
allowed for cheaper motor transport.
Environmental The use of lead based elements is
Impact
destructive to living organisms. Sulphuric
acid is also harmful to the environment
however since lead batteries are
rechargeable they can be reused
minimising the need for disposal. The use
of lead and lead based oxides can are toxic
to all internal organs and the nervous
system. It disrupts the development of the
nervous systems and can leave children
with learning disabilities

Fuel cells have been used in the
space shuttle programs to produce
energy and water for astronauts.
They have great potential if cost is
reduced as a power source of the
future.
Non-polluting as the product is
water. Hydrogen and oxygen
reactants are plentiful. However
hydrogen is explosive which is a
hazard.
Solve problems and analyse information to calculate the potential
requirement
of named electrochemical processes using table of standard potentials and half
equations