Flashcards in 9.2 Production Of Materials Deck (74):
Hydrocarbon +Oxygen —> ?
Carbon dioxide and water
Identify the reason for the high demand for crude oil
High demand for fuels (ie. petroleum and diesel)
The process of breaking down large hydrocarbon molecules into small hydrocarbon molecules
Describe the process of cracking.
Cracking of the process of breaking down large hydrocarbon molecules into small hydrocarbon molecules. Two types:
1. Catalytic cracking: uses inorganic crystal compounds called 'zeolites' to crack large fractions of crude oil into lower molecule weight substances.
2. Thermal/Steam cracking: alkanes and steam is passed through a hot metal tube to compress alkanes into small alkanes. Some hydrogen gas is also produced.
Identify the property of alkenes which make them more reactive than alkanes and describe why this is the case.
The double bond makes alkenes highly reactive. This is because it requires less energy to break one of the bonds in a double bond, than to break a single bond.
What kind of reaction to alkenes undergo?
Addition reactions. Substances react with alkenes by penning the double bond to form two single bonds.
A chemical reaction where many small identical molecules (monomers) combine to form one long molecule (polymer).
Explain why ethylene is an effective monomer
Ethylene's double bond opens up during an addition reaction, allowing adjacent molecules to bond to each other, forming a polymer.
Define polyethylene as an addition polymer
Polyethylene is an addition polymer as is forms by ethylene molecules adding together without the loss of any atoms. The double bond opens up and forming single bonds with adjacent molecules, thus 'adding' to the molecule.
Identify and describe the two process which produce polyethylene
1. High pressure, high temperature and use of an indicator (organic peroxide or oxygen). Product has significant chain-branching - produces LDPE
2. Lower pressure, lower temperature and uses a catalyst. Ziegler Natta process forms unbranched polyethylene molecules which pack closely together - produces HDPE
Explain the role of a catalyst or indicator in the production of polyethylene
Indicators or catalysts active the addition reaction by attaching to an ethylene molecule.
Identify two other polymers used commercially and their monomers.
Poly(vinyl chloride) - vinyl chloride
Polystyrene - styrene
Identify two uses for the three major polymers used commercially.
Polyethylene: milk bottles and cling wrap (LDPE), containers and rubbish bins (HDPE)
Polystyrene: disposable cups (foam and clear) and CD cases
Poly(vinyl chloride): hoses, draining and sewerage pipes.
Describe the uses of polyethylene, polystyrene and poly(vinyl chloride) is regards to its properties.
LDPE: extensive chain-branching makes the molecules soft and flexible. Used for disposable bags, milk bottles
HDPE: lack of chain-breaching, molecules closely packed together makes the molecule strong and hard.
PVC: chain stiffening with polar bonds makes it flexible and soft
Polystyrene: large phenyl side group, stiff and hard. Car batteries and CD cases.
Describe why alkenes are more reactive than alkanes
The double bond in alkenes makes them more reactive as it requires less energy to break a bond in a double bond than to break a single bond.
Recall and describe the experiment where the reactivities of alkenes and alkanes were compared.
Cyclohexane and cyclohexene were reacted with bromine water and observed.
Cyclohexane underwent a substitution reaction as a H ion was replaced by a Br ion (creating HBr and Bromocyclohexane)
Cyclohexene underwent an addition reaction as the Br ions were added to the molecule (creating 1,2 - dibromocyclohexane)
Identify why alternative sources for raw materials that make polymer polymers is needed.
The raw materials used to make polymers are currently sourced from crude oil. As it is a non-renewable resource, thus the source will be depleted. Alternative sources is thus necessary in order to continue producing polymers.
Identify and describe an alternative source for ethylene.
Ethanol is an alternative source for ethylene. It is sourced renewably from the fermentation of starch and sugars, which can be converted to ethylene through a dehydration reaction.
Define: condensation polymer
Condensation polymers that form by the elimination of a small molecule (often water) when pairs of monomers form a polymer.
The reaction releases water.
Identify the two main functional groups that react in a condensation polymerisation.
Amine group (NH2) and carboxylic acid group (COOH)
Describe the reaction that occurs when an amine group reacts with a carboxylic acid group
When the two groups react, a peptide bond is formed. During the condensation reaction, the COOH loses a hydroxyl group (OH) and the amine group loses H.
Describe how proteins are formed as an example of condensation polymerisation.
Proteins are made from amino acids. Amino acids are compounds with an amine group at one and a carboxylic acid group at the other end. As polymerisation occurs, the groups react with each other, releasing water and forming a peptide bond.
Identify the type of reaction which occurs in order to form cellulose.
A condensation reaction between beta-glucose molecule occurs in order to form cellulose.
Explain why cellulose has the potential to be a source of raw materials to make polymers.
Glucose, the basic repeating unit in cellulose, comprises of 6 carbon atoms joined together. This means that it has the basic strutting to produce petrochemicals. If cellulose can be broken into its monomers, then glucose can easily to converted to ethylene.
Identify why cellulose is not yet used as an alternative source of ethylene
It is difficult to break cellulose into glucose because of its long, near-linear chains that connect each monomer.
Name a biopolymer
Identify the microorganism that produces PHB
Outline the method of production of PHB
1. Culture of microorganisms (Alcanlingenes eutrophus) and is fed nutrients (glucose) so that it multiplies rapidly
2. Diet of microorganism is changed to that it no longer increases in population but produces PHB as an energy resource.
3. Organism is harvested and PHB is produced
4. PHB is strong and brittle, so it is produced with polyvalerate, creating PHBV.
Identify the properties of PHB
PHB is strong and brittle, to overcome this, a copolymer is produced by adding polyvalerate (growing bacteria on valerie acid)
PHBV is strong and flexible. It is biodegradable and biocompatible.
Identify the uses of PHBV
biodegradable razor caps, bottle caps, medical sutures.
Describe PHBV potential as a product
PHBV is a strong polymer, so it can be used in situation requiring a durable and flexible material. Its biodegradability makes it an environmentally superior alternative, however, it is more economically expensive to produce.
Describe the current progress in the development of PHB
PHBV was produced as the alternative to PHBV. The gene present in microorganisms to produce PHB can be artificially entered into plants, allowing plants to also produce the biopolymer.
Describe what happens chemically in a dehydration reaction
In a dehydration reaction, water is removed from the molecule.
Ethanol s dehydrated in the presence of concentrated sulphuric acid to produce ethylene and water.
Identify why a catalyst is necessary in a dehydration reaction and the catalyst used in the dehydration of ethanol
The dehydration of ethanol uses concentrated sulfuric acid as a catalyst.
A catalyst is necessary as ethanol is naturally in a stable state, thus will not spontaneously change. The catalyst alters the chemical environment, causing the ethanol to dehydrate
Describe what happens chemically in a hydration reaction
In a hydration reaction, water is added to a molecule.
Ethylene is hydrated in the presence of dilute sulphuric acid to produce ethanol.
Identify why a catalyst is necessary in a hydration reaction and the catalyst used in the hydration of ethanol
The hydration of ethylene uses dilute sulphuric acid as a catalyst.
A catalyst is necessary in order to break the double bond in ethylene.
Identify two uses for ethanol as a solvent
Ethanol can be used in medical preparations (antiseptic) or dissolving food colourings that do not dissolve in water.
Explain why ethanol is a solvent for both polar and non-polar substances
Ethanol can dissolve both polar and non-polar substances due to its structural properties. Its hydroxyl end (OH) is polar and thus attracts oppositely charged dipoles.
It can dissolve non-polar substances due to its alkyl group in which the dispersion forces are attracted to other substances.
Identify the formula for the combustion of ethanol
Ethanol + Oxygen --> Carbon Dioxide + Water
Outline the use of ethanol as a fuel
Ethanol, due to its easily transportable nature, it often used as a fuel source for hikers and campers. Additionally, it is also used as a 'fuel extender'. Current motor vehicles can use petrol with up to 20% ethanol.
Explain why ethanol is both a renewable and non-renewable resource
Ethanol is considered a renewable resource as it can be obtained through photosynthesising plants, which produced glucose. This glucose can then be fermented in the presence of yeast to produce ethanol and carbon dioxide.
Ethanol is also a non-renewable resource as it is most currently sourced from from the creaking of hydrocarbon molecules in crude oil
Describe the conditions under which the fermentation of sugars occurs
In order to ferment sugars to obtain ethanol:
- A suitable grain containing a high conc is starch/sugars is ground with water
- yeast is added
- anaerobic environment
- kept between 30-60 degrees Celsius
Summarise the chemistry of the fermentation process
Enzymes convert starch and complex sugars to glucose/fructose. Other enzymes then convert glucose/fructose to ethanol and carbon dioxide. During the fermentation process, carbon dioxide is given off. This process produces up to 15% ethanol as beyond this point the alcohol begins to kill the enzymes. When fractionally distilled, can produce up to 95% ethanol.
Define the molar heat of combustion
The heat liberated when one mole of the substance undergoes complete combustion with oxygen.
Identify the steps in finding the molar heat of combustion
1. Heat liberated (MCAT)
2. Moles of fuel burnt
3. Heat of combustion (1/2)
Identify 3 advantages and disadvantages of ethanol as a potential fuel source
Advantages: renewable, liquid at room temperature (easily transportable), reduces greenhouse gas emissions.
Disadvantages: not economically viable (more expensive), releases lees energy per gram, additional costs.
identify the catalyst used in the hydration of ethylene
Dilute sulphuric acid
Identify the catalyst used in the dehydration of ethanol
Concentrated sulphuric acid
Summarise a first-hand investigation to carry out the fermentation of glucose to monitor mass change
Glucose, water and yeast were mixed together in a conical flask and then weighed on a weighing balance. Mixture was left for 3 days and remeasured. It was found that the mass had decreased as carbon dioxide was produced and released.
Summarise a first-hand investigation to carry out the combustion of fuels
A spirit burner containing a known fuel is measured and placed under a tripod with a beaker of water. The spirit burner is ignited and allowed to burn for 10 minutes. Flame is extinguished and spirit burner is re-weighed.
Heat of combustion is calculated.
Describe the displacements of metals in a redox reaction
Displacement reactions occur in which a metal converts the ion of another metal into an atom. It occurs in two seperate reactions (reduction and oxidation). It involves the transfer of electrons as the more reactive metals lose their valance electrons (making them an ion), which accepted by the lesser reactive metal (making it an atom). The metal then becomes and ion and goes into solution whilst the atom falls out of solution.
Describe the parameters when considered the oxidation number
1. for a monoatomic ion, the valency is the oxidation state
2. oxygen has an oxidation state of -2, except when in hydrogen peroxide
3. sum of the oxidation state of each atom in a polyatomic ion is equal to the overall oxidation state
4. the oxidation sate of a stable atom is 0
Describe galvanic cells in terms of oxidation and reduction reactions
Redox reactions are used to generate electricity, which is achieved by location the two reaction sites in different locations, with a wire allowing for the travel of lost electrons and a salt bridge.
On the oxidation site of the cell, metals lose electrons and fall into solution. On the reduction site of the cell, metal ions receive the lost electrons and fall out of solution.
Outline the function of the different elements of a galvanic cell
Each reactions site consists of a metal rod in a solution of the same metal. The anode electrode is the site of oxidation whilst the cathode electrode is the site is reduction. A wire connecting the two electrodes allows for the transfer of electrons. A salt bridge allows or electrical neutrality.
Electrons only travel in one direction, from oxidation to reduction.
metal rod where oxidation occurs in a galvanic cell (negatively charged)
metal rode where reduction occurs in a galvanic cell (positively charged)
a conductor which allows electrons to pass through in a galvanic cell
an aqueous or molten solution which conducts electricity
Briefly describe the conditions under which a galvanic cell is produced
- two electrodes of different metals
- two seperate electrolyte solutions, containing the metal that corresponds with the electrode
- electrodes in contact with electrolyte
- salt bridge
Recall the experiment in which the voltage of different galvanic cells was produced. Outline the results
It was found that the metals with the greatest difference in reactivities had the greatest voltage
Outline the chemistry, cost, impact on society and environmental impact of the dry cell
Chemistry: zinc casing (anode), carbon rod (cathode) and aqueous paste of ammonium chloride, manganese dioxide and powered carbon.
Cost: relatively cheap, used for devices requiring small currents.
Impact on society: first commercial battery used, allowing for devices to becomes portable.
Environmental impact: chemical can leak when battery goes flat.
Outline the chemistry, cost, impact on society and environmental impact of the button cell
Chemistry: zinc (anode), silver (cathode)
Cost: provide considerable amount of energy over a constant voltage for a long period of time. Expensive due to silver
Impact on society: small size allows for the production of smaller devices. Non-toxic so can be used inside the body.
Environmental impact: non-recyclable but does not contain by toxic material.
The spontaneous emission of radiation by certain elements
Identify the conditions in which make an isotope unstable
- The atomic number is greater than 83
- the ratio of protons and neutrons is outside the 'zone of stability'
- nucleus is too large
Identify the two ways in which transuranic elements are produced
1. Bombardment of a natural isotope with a neutron
2. Bombardment of a natural isotope with a positive particle (linear accelerator or cyclotron
Describe how a linear accelerator works
A linear accelerator functions by accelerating a positive nucleus (hydrogen ion) through a series of alternate positive and negatively charged tubes. This means that the particle is always being drawn forward and repelled from behind.
Describe how a cyclotron works
A cyclotron functions by accelerating positive particles (hydrogen ions) through positively and negatively charged fields, using a strong magnetic field which contrasts the particle to a spiral path.
Identify and describe the two different processes in which commercial radioisotopes can be produced
1. Nuclear reactor (neutron bombardment): target uncle is placed in a reactor core and bombarded by neutrons (e.g. cobalt-59)
2. Cyclotron (nuclei bombardment): target nuclei is bombarded with small positive particles (helium nucleus) (e.g. Flourine 14)
Identify and describe the four major instruments used to detect radiation
1. Photographic film: worn by lab workers, the darker the film the greater the exposure to radiation.
2. Cloud chamber: contains supersaturated vapour of water or alcohol, which is ionised to create different patterns.
3. Geiger-Muller Counter: radiation enters window of counter, has a gas molecule and ionises it, causes the free electron to ionise others in path - create electric impulse
4. Scintillation Counter: flash of light is emitted, collected and amplified when substance is irradiated by radiation
Identify a radioisotope used in medicine and industry. Include equation
Iodine-131 (treatment) I -> Xe + e + gamma
Iodine-123 (diagnosis) I -> I + gamma
Cobalt-60 (thickness gauge) Co -> Ni + e + gamma
Describe the use of a radioisotope in medicine and relate it to their properties
Iodine-131 is used for treatment (particularly in regards to thyroids) as the beta particles emitted ionise and destroy cells in the body, both unwanted and wanted.
Iodine-123 is used for diagnosis as the highly penetrating gamma rays can detect sites of cancer in the body (eg. PET scan or gamma camera)
Describe the use of a radioisotope in industry and relate it to their properties
Cobalt-60 is used as a thickness gauge in factories. It's low energy emission ensures that the film can absorb most of it and a long half life reduces the frequency of replacements.
Summaries recent discoveries of elements
Recent discoveries of elements have been focusses towards transuranic elements (elements with an atomic number >92) This have been achieved through the bombardment of positive particles in a linear accelerator or cyclotron.
These elements are artificially created and have a very short half life, only existing momentarily.