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Year 12 Chemistry > 1. Production of Materials > Flashcards

1. Production of Materials Flashcards

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1
Q

1.1 What is the industrial source of ethylene?

A

Catalytic cracking - splitting of large hydrocarbon molecules into smaller molecules in the presence of a catalyst

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2
Q

1.1 What are the products of catalytic cracking?

A 
An alkane (with a shorter chain than the original)
An alkene
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3
Q

1.1 Example of catalytic cracking

A

C10H22 -> C8H18 + C2H4 (in the presence of heat and a zeolite catalyst)

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4
Q

1.1 What are the uses of catalytically cracked hydrocarbons?

A

Shorter alkanes can be bended with petrol to increase supply

Alkenes (e.g. ethylene) are useful building blocks for a variety of chemicals

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5
Q

1.2 What property of ethylene makes it readily transformed into many useful products?

A

Alkenes are highly reactive where electrons are more densely held (near the double bond)
To achieve a more even spread of electrons, the double bond must break and form single bonds (and new products)

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6
Q

1.3 What is an example of ethylene serving as a monomer?

A

Ethylene is oxidised with a catalyst, then hydrolysed to form ethylene glycol. This is used as a solvent and to make anti-freeze.
C2H4O + H2O -> HO-CH2-CH2-OH(l)

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7
Q

1.4 What type of polymer is polyethylene?

A

Addition polymer
Polymers are substances made of very long molecules which are made up of smaller units called monomers, covalently bonded together
An addition polymer (such as polyethylene) forms when small molecules add together to form longer molecules, with no other product

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8
Q

1.5 What are the steps in the production of polyethylene?

A
  1. Initiation - a chemical called an initiator starts the reaction by opening the double bond of an ethylene monomer. This forms an ethylene free radical - very reactive molecule
  2. Propagation - the monomer joins, forming a chain
  3. Termination - when free radical ethylene chains combine, a complete molecule is formed and the process stops
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9
Q

1.5 What are the different types of polyethylene?

A

LDPE (low density polyethylene) - Produced under high temperatures and pressures (300ºC). Produces significant chain branching - molecules cannot pack together
HDPE (high density polyethylene) - Produced under low pressures and temperatures (60ºC). Molecules unbranched and pack closely together, creating a more crystalline substance.

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10
Q

1.6 What are two commercially significant monomers?

A 
Vinyl chloride (chloroethene)
Stereo (ethenyl benzene)
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11
Q

1.7 What are the properties and uses of vinyl chloride’s polymer?

A

Polyvinylchloride (PVC)
Rigid, electrical insulator, moderately resistant to chemical attack, impervious to oils and most organic materials
Uses: Water pipes, credit cards, kitchen utensils, electrical insulation, packaging fatty foods, bottles to hold oils and organic materials

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12
Q

1.7 What are the properties and uses of styrene’s polymer?

A

Polystyrene
(expanded polystyrene): low density, lightweight, heat insulator, absorbs shock - floatation devices, styrofoam cups, fast food containers
(crystal polystyrene): hard, clear plastic - rigid items - car batter cases, tool handles, audio cassettes and CD cases

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13
Q

1.8 What is the test for comparing reactivities of alkanes and alkenes?

A

Bromine water test
addition reaction - changes colour from orange to clear when reacted with alkene - double bond breaks and Br atoms are added
Done under fume hood to avoid toxic fumes

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14
Q

2.1 Give three reasons why alternative sources are needed in the petrochemical industry

A
  1. petroleum, natural gas and coal are finite resources - price will increase as stores deplete
  2. 95% used for fuel, 5% for plastics, only small percentage recycled
  3. plastics from fossil fuels are not biodegradable and when burnt as fuel release CO2 and toxic fumes
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15
Q

2.2 What is a condensation polymer?

A

A polymer that forms by the elimination of a small molecule (often water) when pairs of monomer molecules join together. (usually 2 different monomers)

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16
Q

2.3 What groups do common types of condensation polymers from from?

A

monomers containing a carboxylic acid group (-COOH) and either an alcohol (-OH) of amine group (-NH2)

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17
Q

2.3 How many atoms do each of the groups give when forming a condensation polymer?

A

NH2 gives 1H
COOH only gives 1H when combining with -OH, but gives OH when combining with NH2
(all of these combinations create a water molecule)

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18
Q

2.4 Describe the structure of cellulose

A

Flat, straight and right molecule made of repeating glucose units
Hydroxyl groups on the rings are available to hydrogen bond cellulose molecules together side by side -> strong fibres, insoluble

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19
Q

2.5 Why is cellulose suitable to build petrochemicals?

A

because it contains the basic carbon-chain structures

it is the most abundant organic compound on earth - 100bn tonnes produced by plants each year

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20
Q

2.5 What are the benefits of using cellulose as a raw material?

A
  • can only be broken down by certain bacteria, protozoa and fungi
  • resilient to hydrolysis by acids
  • when hydrolysed, produces glucose which can be fermented into ethanol - renewable biomass is converted to evan which normally comes from non-renewable petroleum
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21
Q

2.6 What does PHB stand for?

A

polyhydroxybutyrate

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22
Q

2.6 What are the properties of PHB?

A

insoluble in water, permeable to oxygen, resistant to UV light, biocompatible, high melting point, high tensile strength, biodegradable

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23
Q

2.6 What are some applications of PHB?

A
  • Medical - biodegradability and biocompatibility - dissolving casing, disposable instruments
  • US Navy - cups can be thrown into water
  • Japan - disposable razors - flush down toilets
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24
Q

2.6 What are some limitations of PHB?

A

brittle, higher cost than fossil fuel plastics, more readily available only in developed countries

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25
3.1 Describe the dehydration of ethanol to ethene
Reaction carried out at 350º Catalyst: alumia/porous ceramic catalysts. CONCENTRATED sulphuric acid Sulphuric acid severs the -OH group from the molecule. It is also a dehydrating agent which increases ethene's yield. C2H5OH -> C2H4 + H2O
26
3.2 Describes the hydration of ethylene into ethanol
Reaction carried out at 300ºC Catalyst: dilute sulphuric acid or phosphoric acid C2H4 +H2O -> C2H5OH
27
3.3 Why is ethanol a solvent for polar and non-polar substances
The ethanol molecule has two ends - the polar hydroxyl group (-OH), and the non-polar chain (CH3CH2)
28
3.3 What are some uses for ethanol as a solvent?
Dissolving medicine and food colourings the do not dissolve in water. Water is then added to dilute.
29
3.3 Why is ethanol important as an industrial solvent?
least toxic of all all alcohols, second most important solvent after water. Almost all consumer products listed as containing alcohol have ethanol as a main component.
30
3.4 What is the equation for the combustion of ethanol?
C2H5OH + 3O2 -> 2CO2 + 3H2O
31
3.4 Why does the ethanol molecule almost always combust completely and why is this beneficial?
Because it contains and oxygen atom | This is beneficial because it hardly produces any of the pollution formed from burning other fuels
32
3.4 Why is ethanol considered a renewable resource?
Because it is made from plant material and the products of its combustion are the reactants needed by plants for photosynthesis.
33
3.5 What are some advantages of using ethanol as an alternative fuel?
- Renewable resource - reduce reliability on non-renewable oil. - Ethanol from sugarcane is using a by-product that would make sugarcane production more sustainable - Produces less greenhouse gases than other fuels - can be used up to 10% in petrol without engine modifications
34
3.5 What are some disadvantages of using ethanol as an alternative fuel?
- large areas of land have to be cleared -> soil erosion, deforestation, salinity - if energy for production is derived from fuel combustion, there is no reduction of greenhouse emissions anyway - disposal of smelly waste from fermentation creates environmental issues - ethanol of >10-15% requires expensive engine modifications, as the water content of fermented ethanol causes corrosion
35
3.5 What are some examples of the uses of ethanol as a fuel?
- 1970's - Brazilian government subsidised production of sugarcane -> today approx 25% of vehicles in Brazil use pure ethanol fuel - Australia and the USA produce a limited amount of petrol-ethanol mix - Australian media portrays negative impact on car engines - The use of biofuels enjoys political support worldwide, although this is not translated into action
36
3.6 What conditions are needed to promote the fermentation of sugars?
- Enzymes such as yeast increase the rate of the reaction - Water - the reaction will only take place if the reactants are in a solution - Temp around 37ºC for the fermenting yeast to grow - Low oxygen (anaerobic) - When deprived of oxygen, yeast will respire the sugars anaerobically to obtain energy
37
3.6 At what concentration of ethanol does the yeast die out during fermentation?
14-15%
38
3.7 What are the equations to describe the fermentation process?
- Sucrose reacts with water to form glucose and fructose C12H22O11 + H2O -> C5H12O6 + C6H12O6 - Fermentation then occurs glucose/fructose -> ethanol + carbon dioxide C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)
39
3.8 What is the molar heat of combustion?
the heat liberated when one mole of a substance undergoes complete combustion with the final products being carbon dioxide gas and liquid water. It is exothermic, ∆Hc is always negative
40
3.8 What is the general equation for a molar heat of combustion? Hint: words
alkanol + oxygen -> carbon dioxide + water
41
3.8 What do you need to know to calculate molar heat of combustion?
- Mass of alkanol before and after combustion - mass of water heated - temperature of water before and after the reaction
42
3.8 What are the formulae for ∆Hc?
``` ∆Hc = ∆H/moles (J/mol) ∆H(g) = ∆H/grams (J/gram) ```
43
4.1 The metal with the lowest standard potential is the most/least reactive (choose one)
Most
44
4.1 How are electrons transferred in a displacement reaction?
The more active metal ion loses one or more electrons and becomes a positive ion. The electrons are transferred into the ions of the less active metal, resulting in them forming metal atoms.
45
4.2 What types of ions and atoms are oxidised and reduced?
Atoms of metals and ions of non-metals get oxidised | Atoms on non-metas and ions of metals get reduced
46
4.2 What is the relationship between displacement and relative activity of metals?
If a metal is higher in the reactivity series, the atoms will react in a solution of a lower metal's ions, and the less active metal will be displaced in the solution
47
4.3 How do oxidation numbers and numbers of electrons change with oxidation and reduction?
- A species that undergoes oxidation loses electrons, the oxidation number increases - A species that undergoes reduction gains electrons, the oxidation number decreases
48
4.3 The oxidation number of an atom in elemental form is ____
Zero
49
4.3 The oxidation number of a simple ion is ____
the charge of the ion
50
4.3 The oxidation number of hydrogen is ____
+1 in compounds with non-metals, -1 in compounds with metals
51
4.3 The oxidation number of oxygen in a compound is ____
usually -2. exceptions 1. peroxide compounds (H2O2 and BaO2) where it has oxid. number of -1 2. compounds where oxygen is bonded to fluorine -> +2
52
4.3 In a neutral compound the sum of the oxidation numbers must be ___
Zero
53
4.3 In a polyatomic ion the sum of the oxidation numbers must ____
Equal the charge of the ion.
54
4.4 The metal at the anode ____ electrons
loses
55
4.4 The metal at the cathode ____ electrons
gains
56
4.4 Electrons flow through the ____, from the _____ to the _____
wire, anode, cathode
57
4.6 What are electrodes?
conductors of a cell which get connected to the external circuit
58
4.6 What is the anode?
negative terminal, wehre oxidation occurs. It is always the element that is the most reactive, with the lowest standard potential
59
4.6 What is the cathode?
negative terminal, where reduction occurs
60
4.6 What is an electrolyte?
a solution of metal ions, of the same ion as the electrode in the cell. It conducts an electric current and is decomposed by it
61
4.6 What is the salt bridge?
the ion path between half-cells which keeps electrical balance. the cell will not work without it.
62
4.7 What is standard electrode potential?
Eº = a measure of the strength of reduction reactions compared to hydrogen Eº(cell) = Eº(reduction) + Eº(oxidation) note: use the inverse of the Eº value for the species undergoing OXIDATION
63
5.1 What are isotopes?
atoms of one element that differ by having different numbers of neutrons in their nuclei.
64
5.1 What is a stable nucleus?
a nucleus that will not break down (decay) and emit radiation
65
5.1 What is a radioactive (unstable) nucleus?
a nucleus that will break down to form another nucleus and emit radiation
66
5.1 What is radiation?
a nuclear strong force that outweighs electrostatic repulsion - energy and particles given off by radioactive nuclei
67
5.1 When is a nucleus unstable?
1. when atomic number >83 (Bismuth is the stable element with the highest number of protons) -> loss of alpha particle (2 protons + 2 neutrons) 2. n/p ratio too hight (excess neutrons) -> neutron decays to form proton and beta particle 3. n/p ratio too low -> proton decays to form a neutron and a positron
68
5.2 What is a transuranic element?
an element with an atomic number above that of uranium (Z>93) e.g. neptunium, plutonium and americium, which are produced by neutron bombardment in a nuclear reactor.
69
5.2 What is an example of the production of a transuranic element?
U-238 is bombarded with neutrons and converted to U-239. This undergoes beta decay to produce neptunium and plutonium Pu-239 is then changed to americium through neutron bombardment (upgrade to pro and add image of equation)
70
5.2 How are transuranic elements with atomic numbers over 95 produced?
Using particle accelerators. Small charged nuclei are accelerated. The small particles with high kinetic energy then hit a target of large atoms (upgrade to pro and add image of equation)
71
5.3 Describe 2 methods of commercial production of radioisotopes
1. Bombarding target nucleus with charged particles (in particle accelerator) - ANSTO operates the National Medical Cyclotron for production of radioisotopes for medical use 2. By adding an extra neutron to the target nucleus to produce isotopes that are neutron-rich and therefore radioactive. Source of neutrons: nuclear fission reactor
72
5.3 What is HIFAR and how is it used?
High Flux Australian Reactor, operated by ANSTO at Lucas Heights. The sample is placed in the core of the reactor where it absorbs neutrons and is transformed into a radioactive isotope.
73
5.4 Identify 3 instruments used to detect radiation
``` radiation badge (photographic film) Geiger-Muller counter Scintillation counter ```
74
5.4 How does a radiation badge work?
first detection method: degree of darkening of film is a measure of radiation exposure - worn on lab coats when working with radioactive materials
75
5.4 How does a Gieger-Muller Counter work?
radiation enters a metal tube, causing ionisation of argon atoms, producing free electrons which produce a current which is converted into sound
76
5.4 How does a Scintillation counter work?
Zinc sulphide produces a flash of light when struck by radiation. Flashes are countered electronically to measure and display the amount of radiation.
77
5.5 What is a radioisotope used in industry and how is it used?
COBALT-60 - used in gamma radiology, gauging and commercial medical equipment sterilisation - emits gama rays that provide energy - high penetration ability - can be used to measure thickness of a wide range of metal objects
78
5.5 What is a radioisotope used in medicine and how is it used?
TECHNITIUM-99 - used for imaging e.g. brain, thyroid, lungs liver... and to detect infection - short half-life (6 hours) - long enough to examine, short enough to minimise does to patient when imaging - can be incorporated into biologically-active substances - emits gamma - single energy - not accompanied by beta emission - more precise alignment of detectors
79
5.6 Describe the recent discovery of element 114
Uuq - 1999 - Dubna, Russia - Half life 30 seconds, considerably longer than other heavy elements - created by colliding Ca-48 into Pu-244 target using a heavy ion accelerator - rapidly lost 4 neutrons, resulting isotope decayed by alpha emissions (upgrade to pro and add image of equation)
80
5.6 Describe the discovery of elements 118 and 116
1999 - LBNL team, California - Bombarding lead target with high-energy Krypton ions - Element 116 (Uuh) was identified as a decay product - 2000 - discovery of 116 by bombarding curium-248 with Ca-48 - 2000 - withdrew claims of 1999 discovery because they couldn't repeat the experiment
81
5.7 What are some advantages of the use of radioisotopes in medicine?
- they can prevent, diagnose and treat disease - Prevention: sterilisation of surgical equipment - Diagnosis: used for imaging - Treatment: small doses can be projected or injected, usually post-surgery. Eliminated the need for further invasive procedures
82
5.7 What are some advantages of the use of radioisotopes in industry?
- tracers, to detect leaks in pipes - eliminates need to excavate - mixed with sewage for analysis - very accurate measurement of material depth
83
5.7 What are some problems with the use of radioisotopes in medicine?
- technicians need to avoid being contaminated - diseases such as cancer can result from radiation exposure - technetium-99 capabilities limited due to its short half-life
84
5.7 What are some problems with the use of radioisotopes in industry?
- Cobalt-60 can become mixed with scrap metal and cause contamination if melted in a mill, causing millions of dollars of damage
85
What is an alpha particle?
2 protons and 2 neutrons (a helium nucleus)
86
What is a beta particle?
one electron
87
What is gamma radiation
energy
88
What are the alpha decay rules?
- mass number decreases by 4 - atomic number decreases by 2 - the element changes because the atomic number changes (upgrade to pro and add image of equation)
89
What are the beta decay rules?
- mass number does not change - atomic number increases by one (a neutron changes into one proton and one electron) - the proton remains and the electron is emitted - the element changes (upgrade to pro and add image of equation)
90
Complete the paragraph: After beta or alpha ____, the nucleus which is produced is in an _____ state. It may emit ____ frequency electromagnetic radiation in the form of ______ ____. The nucleus then returns to ____ state.
After beta or alpha DECAY, the nucleus which is produced is in an EXCITED state. It may emit HIGH frequency electromagnetic radiation in the form of GAMMA RAYS. The nucleus then returns to GROUND state.

Year 12 Chemistry (4 decks)

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