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36 Cards in this Set
- Front
- Back
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What is thermal cracking? |
A mixture of long chained hydrocarbons and steam is passed through very hot metal tubes to heat it in order to break the long chains into small alkenes. |
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What is catalytic cracking? |
The heavy crude oil is heated at a lower temp. in the absence of air in the presence of a finely powdered clay zeolite catalyst. |
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Why does ethene have a high reactivity and is readily transformed into many useful products? |
Because of the high reactivity of the double bonds, it can be used as a starting material for other types of organic substances. |
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What are some products derived from ethene? |
Polyethene (plastic film, crates) Ethanol (solvent, drink, fuel) polystyrene (plastic packaging, insulation) |
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Name some properties of ethene |
-Colourless -Gas at room temp -Non-polar -Flammable -Insoluble in water
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What are polymers? |
Long chained molecules composed of repeating sub units called monomers |
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What are the two types of polymerisation reactions? |
Addition and condensation |
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What is an addition polymer? |
Occurs when unsaturated monomers from single, larger molecules. Monomers add to the growing polymer so that all molecules present in the monomer are present in the polymer (no loss of atoms). Require a catalyst or initiator to start the reaction. |
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What was the first hand investigation you used to compare the reactivities of appropriate alkenes with corresponding alkanes? |
-We tested hexane and hexene with bromine water -Only hexene reacted, it immediately changed from a yellow brown colour to colurless -It is the double bond of the alkenes that allows this reaction |
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Describe initiation |
The first step of the polymerisation of ethene. The ethene molecules are activated by the use of an initiator such as peroxide, which opens the double bond of the ethene allowing reaction. The initator dissociates into two free radical segments. The free radical attacks the C=C double bond, transferring the free radical to the end of the chain |
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Describe propagation |
The second step of the polymerisation of ethene. This is where the monomers combine and link together to form a chain. The free radical transfers from monomer to monomer, brekaing the double bonds, allowing them to join together. |
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Describe termination |
Occurs when sufficient monomers have been linked together. Two free radical ethene chains can combine to form a stable covalent bond. The polymerisation process is stopped. |
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What is the systematic name of the polymer of vinyl chloride? |
Polychlorethene |
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What is the common name of the polymer of vinyl chloride? |
Polyvinyl chloride |
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What is the monomer structure of vinyl chloride? |
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What is the systematic name of the polymer of styrene? |
Polyethenylbenzene |
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What is the common name of the polymer of styrene? |
Polystyrene |
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What is the monomer structure of styrene? |
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What are the properties of polyvinylchloride? |
-Thermoplastic -Rigid -Stiff and low flexibility -Water resistant -Low melting point |
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What are the uses of polyvinylchloride? |
-Guttering/pipes -Squeeze bottles -Electrical wire coating -Building materials -Credit cards |
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What are the properties of polystyrene? |
-Rigid -Stiff and low flexibility -Thermoplastic -Light weight -Brittle, hard -Can be turned into plastic foam |
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What are the uses of polystyrene? |
-CD cases -Insulation -Toys -Thermal cups -Utensils |
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Discuss the need for alternative sources of compounds presently obtained from the petrochemical industryh |
-Although there are many petrochemicals, there is a need for alternatives due to the fact they are non-renewable/sustainable and they are pollutants -Our reliance on them has grown because they are easy and cheap -However it has been estimated that petrochemicals will run out within 50-80 years
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Explain what is meant by a condensation polymer |
A compound formed when difunctional monomer molecules join together, forming a polymer and releasing a small molecule such as water by elimination. |
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Describe the reaction involved when a condensation polymer is formed |
-No initiator is necessary in these reactions -When monomers join together, outer parts of the molecules combine to form the eliminated substance, while the rest joins to become a polymer -Condensation polymers do not contain all the atoms originally present |
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What is the structure of cellulose? |
-Consists of glucose monomer -Two glucose monomers react through two hydroxyl groups (OH). An H-OH molecule is condensed out -Bulky CH2OH groups on alternating sides -The hydroxy groups form hydrogen bonds -This bonding resulting in long, strong cellulose fibres |
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How do you get ethene from cellulose? |
-Enzymatic breakdown is the first step, breaking down the cellulose to glucose -The glucose can then be fermented to form ethanol -The ethanol is then dehydrated to ethene |
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Discuss the potential of cellulose as a raw material |
- Currently there is no simple way to break cellulose down into glucose. However, many bacteria and fungi possess cellulase, an enzyme that can break down cellulose into glucose -Biomass fuels cost more than fossil fuels due to the complicated conversion process and its advantages are negated when the energy needed to plant, tend and convert biomass is derived from fossil fuels -Land must also be cleared to make room for the fast-growing crops, creating deforestation. |
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What biopolymer did you make a case study of? What is its monomer? |
Biopolymer: Polyhydroxy butyrate (PHB) Monomer: Hydroxy butanoic acid |
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How is PHB produced? |
-Using a bacteria such as Alcaligenes Eutophus, which is fed a nutrient rich diet until large colonies form. At this point, glucose is restricted from their diet, and as a response the bacteria will secrete PHB as an energy store -The bacteria are harvested and the polymer separated out. The PHB is then milled to a powder or pellet that can be used in moulds |
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What is the development and impact of PHB? |
-The costs of production of biopolymers such as PHB are still too high to be economically viable -Despite this, applications of PHB within the medical industry have been successful; as the non toxic, biodegradable nature of PHB removes the need for follow up surgeries to remove medical sutures as they decompose over time -Due to increasing petroleum prices and descreasing PHB production costs, it may be possible for PHB to encounter greater usage |
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Evaluate PHBs uses based on its properties |
-Biodegradable: Large environmental advantage, as it is able to decompose into carbon dioxide and water -Physically similar to polypropylene: Can be used as a substitute -Durable, flexible, easily moulded: Wide range of uses as a plastic eg containers -Compatible with blood and tissues of mammals: Used as a surgical implant as seam threads for the healing of wounds |
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Describe the dehydration of ethanol to ethylene and identify the need for a catalyst in this process and the catalyst used |
-Ethanol can be converted into ethene through the dehydration of ethanol -This process uses concentrated sulfuric acid as a catalyst -When heated with the acid as a catalyst, an ethanol molecule loses an OH group and an H atom on the adjacent carbon to give an ethene -The catalyst is used to lower the activation energy, as the reaction is exothermic the temp cannot be too high of the yield of ethene is reduced -The catalyst also absorbs water formed to prevent the reaction from reversing |
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Describe the addition of water to ethylene resulting in the production of ethanol and identify a need for a catalyst in this process and the catalyst used |
-The water molecule breaks the double bond of the ethene and adds into the molecule -Dilute sulfuric acid is used as a catalyst |
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Describe and account for the many uses of ethanol as a solvent for polar and non polar substances |
-Ethanol is a polar molecule due to the (OH) group -The oxygen is more electronegative than the carbon or hydrogen, forming a dipole -It also has non polar C-H intramolecular bonds, meaning it is also non polar |
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What are some uses of ethanol as a solvent? |
-Food colourings and flavourings -A solvent in medicines eg cough mixtures -Varnishes and plastics -Cosmetics eg. deodorants and perfumes -Methylated spirits |
