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Chemistry > Production of Materials > Flashcards

Production of Materials Flashcards

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1
Q

What is the industrial source of ethylene?

A

Ethylene comes from the cracking of some of the fractions from the refining of petroleum

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2
Q

Name the conditions and steps for the thermal cracking of a Naptha Fraction

A

CONDITIONS:
-750-950 degrees, high pressure
STEPS:
1. Initiation (free radicals form)
2. Propagation (radicals decompose to form smaller free radicals and alkenes)
3. Termination (free radicals meet with other free radicals to form hydrocarbons)

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3
Q

Name the catalyst and conditions necessary for catalytic cracking

A

Catalyst:
-zeolite (an aluminium silicate)
Conditions:
-lower temp. than thermal cracking (500 degrees)

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4
Q

What are the advantages of catalytic cracking over thermal cracking?

A
  • Lower activation energy

- Higher surface area for reaction to occur

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5
Q

Name each type of reaction the alkene can undergo to produce useful products

A
  • Hydration
  • Hydrogenation
  • Oxidation
  • Halogenation
  • Alkylation
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6
Q

Name at least three useful products that ethylene can be transformed into

A
  • Ethane
  • Ethanol
  • Ethylene glycol
  • PVC
  • Ethyl benzene
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7
Q

Define polymer

A

Polymer - a large molecule formed when many identical monomers combine

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8
Q

Define addition polymer

A

A polymer formed by addition reactions, where many monomers bond together via rearrangement of bonds without the loss of any atoms or molecules

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9
Q

Name the polymer produced by the Gas Phase Method and the relative conditions of the method

A
  • produces LDPE

- relatively high temperature and pressure

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10
Q

Name the polymer produced by the Ziegler Natta Method and the relative conditions of the method

A
  • produces HDPE

- relatively low temperature and pressure

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11
Q

Name one property and use of LDPE

A 
PROPERTIES:
-lower density than HDPE
-forces of attraction between polymer molecules are weakened
-material isn't as strong and has lower melting point than HDPE
USES:
-cling wrap
-wire and cable
-extrusion coating
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12
Q

Name one property and use of HDPE

A 
PROPERTIES:
-rigid
-translucent, white
-melting point higher than LDPE
-chemically stable
USES: bowls, buckets, freezer bags, petrol tanks
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13
Q

Name a property of PS and a use that the property provides?

A

Stiff and rigid > long lasting > useful for stools, cases

Transparent > can see products > CD cases

Insulator > keeps food warm > takeaway containers

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14
Q

Name a property of PVC and a use that this property provides

A

Unreactive/UV stable (with additive) > will not degrade > plumbing

Rigid and tough, strong IM bonding > withstands force > floor tiles

Infexlible because of chlorine holding chains > won’t move too far under force > plumbing

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15
Q

Discuss one need for alternative sources of the compunds presently obtained from the petrochemical industry

A
  • some analysts predict that oil supplies will be effectively fully depleted by the middle of the century
  • currently there is pressure to reduce energy use and to develop alternatives partly because of the greenhouse effect that the burning of fossil fuels has on the atomsphere and partly because as oil supplies diminish its cost will increase
  • some scientists argue that as oil prices increase it will become too expensive to use as fuel and a shift to alternative sources will result in the remaining oil becoming the exclusive domain of the petrochemical industry, lasting for many more decades
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16
Q

Define condensation polymer

A

Condensation polymer - a polymer that forms by the elimination of a small molecule (often water) when pairs of monomer molecules join together

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17
Q

Describe the structure of cellulose

A
  • the many polar hyodroxy groups that exist along cellulose chains form hydrogen bonds with those on adjacent chains
  • bonding causes the bundling of cellulose chains
  • results in great length and strength of cellulose fibres
  • reduced availability of hydroxy groups due to their involvement in hydrogen bonding makes cellulose insoluble and reasonably resistant to chemical attack

http://imgur.com/a/aVvZY

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18
Q

Describe the reaction involved when a condensation polymer (cellulose) is formed

A
  • cellulose is formed from β-glucose molecules
  • when two glucose monomers react, a hydroxyl group from each combine to condense a water molecule, leaving an oxygen atom linking the two monomers

http://imgur.com/a/pIixc

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19
Q

Discuss glucose’s potential as a raw material

A
  • cellulose contains many carbon, hydrogen and oxygen atoms
  • hence, it is a good source of the basic carbon chain structures that are required to produce compounds currently obtained from the non-renewable petrochemical industry
  • cellulose can be broken down to obtain ethylene, which is currently obtained from the petrochemical industry
  • process is currently not economically viable due to the many number of steps need for ethylene to be produced
20
Q

Analyse the development and use of polyhydroxybutyrate (PHB)

A
  • PHB is a polyester that is manufactured by growing bacteria in a high glucose environment with the bacteria producing the biopolymer and storing it in there cell walls where it is then extracted
  • it is used for biodegradeable plastic products (e.g. shampoo bottles)
21
Q

Account for ethanol’s dual nature as a solvent

A
  • the presence of a polar and non-polar region in ethanol accounts for its dual nature as a solvent
    http: //imgur.com/a/T9CeZ
22
Q

Account for the usefulness of ethanol as a solvent

A

The polar OH end is able to dissolve polar solutres by forming hydrogen bonds, dipole-dipole interactions or ion-dipole interactions depedining on the solute (e.g. ethanol dissolving in water)

http://imgur.com/a/CWYw1

23
Q

Account for the usefulness of ethanol as a non-solvent

A

Ethanol can dissolve non-polar solutes such as iodine or hexane by forming dispersion forces between the solute molecules and the non-polar hydrocarbon end of ethanol

http://imgur.com/a/jSQWv

24
Q

Describe the hydration of ethylene to ethanol

A

http://imgur.com/a/jXbN6

25
Q

Describe the dehydration of ethanol

A

http://imgur.com/a/L6xX3

26
Q

List the conditions under which the fermentation of sugars is promoted

A
  • aqueous solution of glucose (10% w/v)
  • alchol tolerant yeast
  • nutrients for yeast (Pasteur’s salt)
  • temp. about 37 ˚
  • Anaerobic conditions (closed vessel, no air)
27
Q

Describe the fermentation process (of glucose)

A

http://imgur.com/a/ycP67

28
Q

Differentiate between and exothermic and endothermic reaction

A

Endothermic reaction = energy absorbed = bonds breaking

Exothermic reaction = energy released = bonds forming

29
Q

Name one advantage and one disadvantage of using ethanol as an alternative fuel

A

ADVANTAGES:

  • more likely to undergo complete combustion compared to a fossil fuel (such as octane), hence minimising toxic products produced as a result of incomplete combustion
  • produces less carbon dioxide
  • ethanol requires less oxygen for combustion to occur
  • ethanol is ‘clean’ and better for engines (its dual polar/non-polar nature allows it to dissolve deposits in the engine)

DISADVANTAGES:

  • produces a quarter of the energy of octane when burnt
  • land used for growing crops whose sugars undergo fermentation may be better used for food crops instead
  • process of processing ethanol into a fuel is not economically viable as it requires a large amount of energy
  • current cars would require engine modification
30
Q

Define ‘displacement reaction’

A

Displacement reaction - one in which a metal converts the ionised version of another atom to its neutral state (i.e. complete outer shell)

http://imgur.com/a/TxQFv

31
Q

Why are metal displacement reactions important

A

They can produce electricity through the transfer of elections. Reactive solid metals can transfer their valence electron(s) to cations of less reactive metals.

32
Q

Distinguish between and oxidant and a reductant

A

Reductant/reducing agent: donates its electrons

Oxidant/oxidising agent: accepts electrons

33
Q

What is the relationship between the displacement of metal ions in a solution by other metals and the relative activity of metals

A

The more reactive metal is the one which will displace the other metal from a solution from its ions.

34
Q

Describe galvanic cells in terms of oxidation/reduction reactions

A

A galvanic cell is an electrochemical cell that uses spontaneous chemical reactions to produce electricity. The chemical reactions are classified as redox reactions - since these reactions are simultaneous, the number of electrons being transferred must be the same.

35
Q

Outline the construction of a galvanic cell

A
  • a galvanic cell is constructed from to half cells (one half is the oxidation half cell; the other is the reduction half cell)
  • suitable electrodes are placed in each half cell (for example zinc and copper)
  • electrolyte is then added to ensure the electrodes are dipping into them (electrode - a substance with freely moving ions)
  • e.g. zinc nitrate for zinc electrode and copper (II) nitrate for copper electrode
  • since zinc is more reactive than copper, oxidation will occur at the zinc electrode (anode) while reduction will occur at the copper electrode (RED CAT, AN OX)
  • the salt bridge connects the 2 half cells so that ions are able to move between them
  • wire is used to connect the two electrodes and electrons are transferred from one electrode to the other via the wire
  • anions towards anode, cations towards cathode

http://imgur.com/a/nmruX

36
Q

What is an isotope?

A

An isotope is an atom that has the same atomic number but a different mass number e.g. C-12, C-13, C-14

37
Q

What are the two main factors that affect the stability of an isotope?

A
  1. Mass of the nucleus

2. Ratio of neutrons to protons (neutron rich/neutron deficient)

38
Q

What is an alpha particle?

A

An alpha particle is a helium nucleus (2 protons, 2 neutrons)

39
Q

What type of nuclei tends to emit a beta particle?

A

A beta particle is an electrons

40
Q

What type of nuclei tends to emit a gamma ray?

A

A gamma ray is a form of electromagnetic energy

41
Q

How are transuranic elements (atomic no. >92) produced?

A
  • transuranic elements can be made by neutron bombardment in a nuclear reactor or particle bombardment in a particle accelerator
  • in particle bombardment, particles are accelerated to near the speed of light and as they move faster, collisions occur between particles, resulting in nuclear radiation and the formation of new substances
  • neutron deficient atoms are produced in a particle accelerator, acceleration is necessary to overcome the postie charge of the nucleus

http: //imgur.com/a/0Qi0y
- neutron rich atoms are produced in a nuclear reactor
http: //imgur.com/KSxLAvh

42
Q

Identify two methods of detecting radiation

A
  • the Geiger-Müller tube is best at detecting alpha and beta radiation as these are more ionising than gamma radiation
  • the tube is filled with an inert gas. There is a central anode with a positive charge and a cylindrical casing which is the cathode and negatively charged. A voltage is then applied.
  • as the ionising radiation enters the tube, it ionises the argon has to produce argon ions and elections. The electrons are attracted to the positive central anode while the gas ions move towards the positive cathode
  • the electrons are accelerated by providing a high voltage resulting in more inert gas ionising, leading to an avalanche of electrons at the anode creating an amplified electrical pulse, which is detected by a digital counter

-another method of detecting radiation is penetration power

43
Q

Describe the recent discovery of one element

A

Tennessee is the name given to the element with atomic number 117. It was produced in a cyclotron by bombarding Berkelium nuclei with calcium ions accelerated to speeds near the speed of light, it was discovered in 2010.

Oganesson was first synthesised in 2002 by bombarding target Californium 249 nuclei with accelerated Calcium 48 ions.

44
Q

Describe how a radioisotope is used in industry and the benefits and costs associated with its use

A
  • Strontium-90, as it is able to penetrate aluminium foil, and is therefore used in industry for thickness gauges
  • the Sr-90 beta source is placed behind the material, which will have its material tested and the amount of radiation that penetrates it is detected on the other side. If there has been wear and tear on the material and it has become thin, then high levels of radiation will be detected

ADVANTAGES:

  • strontium has a half life of 28.8 years, meaning that is can be used for many years without the need for replacement, which is one of the benefits of using it in industry
  • it also allows a quick and accurate way of determining thickness which helps quality assurance of materials

DISADVANTAGES:
-those handling Sr-90 need to take care to minimise their exposure to the beta radiation produced otherwise bone cancer or other cell abnormalities can result

http://imgur.com/a/xWXi3

45
Q

Describe how a radioisotope is used in medicine and the benefits and costs associated with its use

A
  • radioisotopes that produce gamma ways and have a short half life are desirable to minimise the patient’s exposure to radiation
  • Technetium-99m is suitable as a result, as it has a half life of just 6 hours
  • the gamma rays it produces can be detected by a camera as they pass through the body and after 2 days there are negligible amounts of radiation left in the patient
  • Tc-99m is combined with a tin compounds with a tin compound which binds to red blood cells, allowing for any disorders to be detected by abnormal blood flow

ADVANTAGES:

  • using Tc-99m include early detection of tumours an abnormalities so prompt action can be taken by health practitioners
  • gamma radiation it emits is non-ionising (unlike alpha and beta radiation), hence not affecting the structure of DNA and other chemicals in organisms resulting damage to tissues

DISADVANTAGES:

  • health tissue may be exposed to the radioisotope
  • handlers of Tc-99m need to take care by using protective syringes and disposing of them appropriately

http://imgur.com/a/I0p3E

Chemistry (1 decks)

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