Chemistry- Production of Materials (1 Viewer)


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Oct 29, 2007
Production of Materials
1. Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum
Petroleum is a mixture of hydrocarbons.
When petroleum undergoes fractional distillation, some fractions, particularly petrol, are in demand and of high economic value.
Other fractions, consisting of larger molecules than in petrol and of low value, can be passed over a heated catalyst that cracks the larger molecules into smaller molecules.
A major by product of this catalytic cracking is ethylene, also known as ethene
Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products
Ethylene is a more reactive molecule than ethane or other alkanes.
The high reactivity of its double covalent bond allows it to be chemically transformed into a wide variety of useful products including polymers (mainly polyethylene) and many other petrochemicals.
Ethylene is produced from natural gas or crude oil, which are mixtures of hydrocarbons.
Ethylene can be used for plastics, guttering, soft furnishings etc.
Identify that ethylene serves as a monomer from which polymers are made
Ethylene is an important monomer.
Ethylene undergoes addition polymerisation to form polyethylene.
In this process, the ethylene monomers undergo addition reactions and the double bond breaks.
The polymer consists of long branched or unbranched chains of various lengths depending on the polymerisation conditions
Identify polyethylene as an addition polymer and explain the meaning of this term
Polyethylene is called an addition polymer.
Addition polymerisation- is a process in which unsaturated monomers combine by the process of addition.
Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer
Two different forms of polyethylene can be manufactured, depending on the reaction conditions.
To produce low density polyethylene (LDPE), a peroxide containing an O-O bond that breaks easily forming free radicals is used to initiate the joining of ethylene monomers. The process must occur under high gas pressure to produce LDPE. These production conditions result in molecules with the short branches that characterise LDPE.
To produce high density polyethylene (HDPE), low gas pressures and a catalysts made of transition metals and organometallic compounds enables more ordered orientation of ethylene to form the long unbranched and aligned molecules in HDPE.
Identify the following as commercially significant monomers:
- Vinyl chloride
- Styrene
by both their systematic and common names
Two commercially important monomers are vinyl chloride (Cl) (chloroethene) and styrene (C6H5)(ethenylbenzene or phenylethylene) . These are the monomers which form the widely used products known as polystyrene and polyvinyl chloride or PVC, which are widely used in packaging and many other high-demand areas.
Describe the uses of the polymers made from the above monomers in terms of their properties
Name of polymer
Vinyl Chloride (Polyvinyl Chloride)
Rigid because the chlorine side group is larger than hydrogen. This makes it stiff and reduces flexibility Water resistant, Thermoplastic, Low MP
Pipes, electrical wire coating, building materials, guttering, flooring, credit cards
Styrene (Polystyrene)
Rigid because the benzene side group is larger than hydrogen. This makes it stiff and reduces flexibility, Thermoplastic, turned into plastic foam (traditionally by using CFC’s) lightweight, hard
CD cases, insulation, toys and utensils, thermal cups for tea and coffee, tool handles

2. Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry
Petrochemicals are chemicals made from compounds in petroleum or natural gas.
Currently Australia has petroleum reserves that will last about ten years and natural gas reserves that will last about one hundred years.
Fossil fuels have taken hundreds of millions of years to accumulate. 95% of the compounds presently obtained in the petrochemical industry are burnt as fossil fuels for energy purposes.
Less than 5% of fossil fuel is used to make plastics and only a small percentage of that plastic is recycled.
If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are used up.
One important candidate is biomass. Biomass is a renewable resource.
Explain what is meant by a condensation polymer
Condensation polymer is when two monomers combine with the elimination of a smaller molecule, usually water.
Describe the reaction involved when a condensation polymer is formed
A condensation polymer is formed by monomer molecules condensing out small molecules (such as water) as the polymer chain forms.
Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass
Cellulose is a flat, straight and rigid molecule.
Identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material
A three carbon-chain and a four carbon-chain are present within the structure of a glucose monomer in a cellulose chain. These carbon-chains have attached hydrogen and hydroxy groups
The carbon-chain sections could be changed to chemicals that, at present, are mostly made from petroleum. If a chemical process can be developed or a micro-organism found that can break the glucose into three carbon-chains and four carbon-chains this would be very useful.
Use available evidence to gather and present data from secondary sources and analyse progress in the recent development and use of a named biopolymer. This analysis should name the specific enzyme(s) used or organism used to synthesise the material and an evaluation of the use or potential use of the polymer produced related to its properties
Biopolymer: polyhydroxy butyrate (PHB)
Is a member of the biopolymer family polyhydroxyalkanoates (PHAs).
Monomer- b-hydroxybutanoic acid
The development of PHB
In 1925, Maurice Lemoigne of the Pasteur Institute in Paris found that certain bacteria grew PHB to store energy (like starch in plants and fat in mammals).
Production of PHB
Bacteria like Alcaligenes Eutrophus are used to produce the biopolymer PHB, the bacteria are allowed
to grow in a suitable medium while being fed high large amounts nutrients (normally glucose), and this causes the bacteria to reproduce rapidly into a large population.
Excellent flexibility
Very tough
Degrades quickly anaerobic conditions
Use in cosmetic containers, including shampoo:
Durability: Practical, less risk of breakage
Flexibility: allows contents to be squeezed out.
Slow aerobic degradation: Container wont degrade before contents are used
PHB has great potential for use where biodegradability is of concern. Possible applications include disposable nappies and packaging, particularly packaging for medical and hospital supplies.

3. Describe the dehydration of ethanol to ethylene and identify the need for a catalyst in this process and the catalyst used
Ethanol Ethene Water
A catalyst, (concentrated H2SO4), is used to lower activation energy.
The forward reaction is exothermic and so the temperature of the system must not be too high (180°C) otherwise the yield of ethene is reduced.
This catalyst also absorbs the water formed to stop the reaction from reversing.
Describe the addition of water to ethylene resulting in the production of ethanol and identify the need for a catalyst in this process and the catalyst used
A catalyst, dilute H2S04 is used to lower activation energy.
Describe and account for the many uses of ethanol as a solvent for polar and non polar substances
Ethanol is used as a solvent in dissolving medicines, food flavourings and colourings that do not dissolve easily in water.
The ethanol molecule has a water loving (hydrophilic) -OH group that helps it dissolve polar molecules and ionic substances. The short, water fearing (hydrophobic) hydrocarbon chain CH3CH2- can attract non-polar molecules. Thus ethanol can dissolve both polar and non-polar substances.
Industrially and in consumer products, ethanol is the second most important solvent after water.
Ethanol is the least toxic of all the alcohols as it is poisonous in moderate amounts rather than small amounts.
Consumer products listed as containing alcohol practically always contain ethanol as the alcohol.
Outline the use of ethanol as a fuel and explain why it can be called a renewable resource
Ethanol combusts in air, releasing carbon dioxide and water.
Because the ethanol molecule contains an O atom, the combustion is practically always complete. C2H5OH(l) + 3O2(g) --à 2CO2(g) + 3H2O(g)
There is hardly any formation of the polluting CO or C forms, which form from the incomplete combustion of many other hydrocarbons and thus is used as a fuel.
Ethanol is promoted as a fuel for motor cars etc.
Ethanol can be called a renewable resource because ethanol can be made from plant material and the products of its combustion, carbon dioxide and water, are the reactants needed by plants for photosynthesis.
Describe conditions under which fermentation of sugars is promoted
Fermentation- is a biochemical process in which sugars are turned into ethanol
The conditions that promote the fermentation of sugar are:
suitable micro-organism such as yeast
suitable temperature for the fermenting yeast
low oxygen concentrations favouring the fermenting yeast
small amount of yeast nutrients such as phosphate salt.
Once the ethanol concentration reaches 14-15% by volume, the yeast cannot survive, and the fermentation process stops.
Summarise the chemistry of the fermentation process
Enzymes (biological catalysts) in the mixture convert any starch or sucrose in the mixture into glucose, then other enzymes convert glucose or fructose into ethanol and carbon dioxide.
Bubbles of carbon dioxide are slowly given off. Yeast can produce ethanol contents up to about 14-15%. Alcohol concentrations above this level kill the yeast and stop further fermentation. To produce higher alcohol concentration the liquid is distilled
Define the molar heat of combustion of a compound and calculate the value for ethanol from first hand data
The molar heat of combustion is the heat change when one mole of the substance is combusted to form products in their standard states (that is, solid, liquid or gas) at 105 Pa (100 kPa) and 25oC (298K).
Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use
Ethanol is considered a renewable resource because ethanol is a biomass fuel
Advantages of ethanol as an alternative fuel include:
It is complete combustion with minimal pollution. It can also be made in a number of ways.
Lower ignition temperature than petrol
When ethanol is added to petrol, or used on its own, the amount of polluting gases such as carbon monoxide (CO) and hydrocarbons is reduced.
Disadvantages of ethanol as an alternative fuel include:
The energy needed to produce the ethanol is substantial, particularly the distillation needed to separate alcohol from water
Large areas of agriculture needed to cultivate
Ethanol is more expensive than petrol
Problems with disposal
Identify the IUPAC nomenclature for straight chained alkanols from C1 to C8
Number of carbon atoms



Process information from secondary sources to summarise the processes involved in the industrial production of ethanol from sugar cane

Process information from secondary sources to summarise the use of ethanol as an alternative car fuel, evaluating the success of current usage

4. Explain the displacement of metals from solution in terms of transfer of electrons
More active metals will displace less active metal ions from solution in an oxidation-reduction reaction.
When an active metal is placed in a solution containing ions of a less active metal, the active metal displaces the less active metal from solution. This occurs because a more active metal atom loses one or more electrons and becomes a positive ion. The electrons lost are transferred to the ions of the less active metal, resulting in them becoming metal atoms.
Identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metals
If a metal is higher in the activity series, the metal atoms will react when put in a solution of ions of a metal that is lower in the activity series. The less active metal ions are displaced from solution as they form atoms.
Account for changes in the oxidation state of species in terms of their loss or gain of electrons
Describe and explain galvanic cells in terms of oxidation/reduction reactions
A galvanic cell is a device which makes a chemical reaction occur in such a way that it produces electricity.
A galvanic cell is a device constructed so that a reductant and oxidant are physically separated, but connected by an external circuit made of a conductor (to carry electrons) and a salt bridge (to carry charged ions in solution). A galvanic cell is thus composed of two half-cells, a reductant half-cell and an oxidant half-cell. This arrangement ensures that electrons cannot go directly from the reductant to the oxidant, but they will move through the external circuit.
Outline the construction of galvanic cells and trace the direction of electron flow

Define the terms anode, cathode, electrode and electrolyte to describe galvanic cells
Electrode: solid conducting rod in an electric cell where electrons are exchanged
Anode: the electrode at which oxidation occurs. It is the more reactive of the two electrodes (eg. zinc). It is negative
Cathode: The electrode at which reduction occurs. It receives the electrons and is the least reactive of the pair (eg. copper). It is positive
Electrolyte is a conductive solution (eg. KNO3(aq)).
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 (eg the Gratzel cell)
- Chemistry
- Cost and practically
- Impact on society
- Environment impact

Solve problems and analyse information to calculate the potential E requirement of named electrochemical processes using tables of standard potentials and half equations

5. Distinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is unstable
Isotopes are elements that have the same atomic but different mass numbers.
A stable isotope is a form of an element which is not radioactive.
A unstable radioisotope emits radiation and are called radioisotopes They have an unstable ratio of neutrons to protons.
Describe how transuranic elements are produced
Transuranic elements are elements with an atomic number above that of uranium with atomic number Z= 92.
Transuranic elements such as Uranium- 238 can be produced by being bombarded with neutrons produced by the nuclear fission of U-235.
Another method of making transuranic elements is to bombard target nuclei with the nuclei of other elements using particles accelerators.
Describe how commercial radioisotopes are produced
Commercial radioisotopes are produced by accelerators and nuclear reactors.
Many commercially used radioisotopes are created at nuclear reactors.
When the uranium nucleus breaks up into two nuclei, many different isotopes are formed.
Differences in chemical properties of the elements produced can be used to chemically separate the different radioisotopes.
The high-speed neutrons emitted can be used to bombard atoms of various elements to produce useful neutron rich isotopes.
Identify instruments and processes that can be used to detect radiation
The Geiger-Muller tube contains gas that ionises and produces a small pulse of electricity each time it is ionised by radiation. The counter counts the number of pulses.
Low energy radiation that is too weak to ionise atoms is called non-ionising radiation and can be detected by a scintillation counter
Cloud Chamber
Identify one use of a named radioisotope:
- In industry
- In medicine
In industry
Cobalt-60 (Co-60) is used in a process called industrial radiography, to inspect metal parts and welds for defects.
In medicine
Technetium-99m (Tc-99m) is used in a wide range of medical applications, such as pinpointing brain tumours.
Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their chemical properties
Industrial- Cobalt-60 is used in industrial radiography to inspect metal parts and welds for defects.
Beams of radiation are directed at the object to be checked from a sealed source of Co-60.
Radiographic film on the opposite side of the source is exposed when it is struck by radiation passing through the objects being tested.
More radiation will pass through if there are cracks, breaks, or other flaws in the metal parts and will be recorded on the film. By studying the film, structural problems can be detected.
Co-60 is used because it is an emitter of gamma rays which will penetrate metal parts. Co-60 has a half-life of 5.3 years and can be used in a chemically inert form held inside a sealed container. This enables the equipment to have a long lifetime and not require regular maintenance.
Technetium-99m (Tc-99m) is used in over half of the current nuclear medicine procedures, such as pinpointing brain tumours.
Tc-99m can be changed to a number of oxidation states. This enables production of a wide range of biologically active chemicals.
The Tc-99m is attached to a biological molecule that concentrates in the organ to be investigated.
Tc-99m is used because it has a very short half-life of 6 hours which is lone enough for medical investigations and short enough to minimise the patients exposure to radiation, it emits low energy gamma radiation that minimises damage to tissues but can still be detected in a person's body by a gamma ray sensitive camera and it is quickly eliminated from the body.
Technetium is reasonably reactive; it can be reacted to form a compound with chemical properties that leads to concentration in the organ of interest such as the heart, liver, lungs or thyroid.

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