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Yr 12 Chemistry > Production of materials > Flashcards

Production of materials Flashcards

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1
Q

What is catalytic cracking?

What are the conditions for this?

A

used to industrally produce ethylene

  • breaking long chain hydrocarbons into smaller molecules.(into ethene)
  • moderate temperatures (500 degrees approx.)
  • the use of the catalyst zeolite (increases SA)
  • the absence of air
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2
Q

What is an example of catalytic cracking?

A

C10H22 –(zeolite)–> C8H18 + CH2CH2
decane –> octane + ethylene
***One product is always an alkane, the other is an alkene.
The products of cracking are then separated by fractional distillation

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3
Q

What property of hydrocarbons allow separation to occur?

A

Different boiling points

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4
Q

What are the first 8 hydrocarbons of alkane & alkene series?

A

meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-,

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5
Q

what is petroleum made up of?

A

fossil fuels, natural gas & crude oil -> mixtures of different hydrocarbons (from gases:Methane to liquids-octane)

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6
Q

What is thermal/steam cracking?

What are the conditions for this?

A
  • breaks down hydrocarbons into smaller molecules (ethene)

- long chain HC’s passed through metal pipes (pyrolysis coils) with steam (700-1000degrees)

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7
Q

Alkanes react with oxygen to form?

A

H20 +CO2 (heat is required)
Combustion reaction: methane +O2
Substition reaction: Heptane & O2

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8
Q

Why does the separation of hydrocarbons occur?

A

because the demand for short chain molecules is greater than the supply so molecules are broken up.

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9
Q

Alkanes also react with what in the presence of light?

A

Halogens

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10
Q

Why are alkenes so much more reactive than alkanes?

A

The presence of the double bond

REDO ANSWER!!

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11
Q

What is the laboratory test for alkenes/alkanes?

A

Drops of bromine water added to cyclohexane and cyclohexene

turns clear :alkene

no colour change:remains(brown) alkane, exposed under uv light it will slowly react

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12
Q

Due to the double bond in alkenes they easily react in:

_______________ Reactions

A

Addition reactions.

The bond opens up and another atom joins the molecule

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13
Q

As the size of a molecule Increases:

A

So to do dispersion forces

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14
Q

Alkenes are unsaturated/saturated ?

A

Alkenes have a double bond and therefore are unsaturated

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15
Q

Akanes are:

A

Saturated due to their single bond

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16
Q

What is polymerisation?

A

The joining together of monomers to form a polymer chain

NO NEW PRODUCT!!

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17
Q

What happens in the polymerisation of ethylene?

A

–> polyethylene. It is an addition polymerisation (forms without the loss of atoms ) due to double bond

CH2=CH2=CH2=CH2
                  ⬇️
-CH2-CH2-CH2-CH2-CH2-CH2-
                    ⬇️
         -(-CH2-CH2-)-
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18
Q

What are the 2 main types of polyethylene produced?

A

Low Density Polyethylene

High Density Polyethylene

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19
Q

cellulose has basic carbon chain structures need for petrochemicals discuss the potential of cellulose as a raw material to build petrochemicals:

A

ADV:

  • is renewable
  • made from structures that would otherwise be disregarded & hard to dispose

DISADV:

  • It is an expensive process
  • energy for the process would mostly come from oil, making it less renewable & unsustainable
  • ethical issue of growing crops for plastic, while people starve
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20
Q

What happens in the deyhdration of ethanol?

A

Used to make alkenes from alkanols
-involves removing water molecules from a substance.
ethanol is dehydrated by heating it with CONCENTRATED sulfuric acid (as it has to break strong covalent bond)

C2H5(g) –> C2H4(g) + H2O(g)

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21
Q

What happens in the hydration of ethlyene?

A

It is used to make alkanols from alkenes
- involves adding water molecule across the double bond of ethylene.
ethylene(g) is hydrated with water molecules when heated when heated with DILUTE sulfuric acid to form ethanol (the reactive double bond of ethylene means it is a weaker dilute catalyst)

C2H4(g) + H20(g) –>C2H5OH(g)

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22
Q

Why is ethanol polar & non polar?

A

polar: the (OH) group, meaning H bondin occur, attraction polar & ionic molecules

non polar: the ethyl (C2H5) group is non-polar, attracting non-polar molecules

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23
Q

Is ethanol both polar and non-polar?

if so what products is it used in because of this?

A

it is both polar & non polar, therefore can dissolves the substances water can’t dissolve .eg. grease
it is used in cosmetics (perfume, antiseptics, cleaning agents

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24
Q

what are the conditions under which the fermentation of sugars is promoted?

A
  • 20%glucose in (aq) solution
  • slightly acidic pH (prevent bacteria growth)
  • at 30-37C
  • yeast
  • in an anoxic environment

C6H12O6(aq) –> 2C2H5OH(l) + 2CO2(g)

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25
Q

Describe the structure of cellulose

A

a condensation polymer from the polymerisation of glucose

Long chain of alternating beta glucose monomers that are linked in strong covalent bonds & H bonds.
This means cellulose is:
linear, rigid, strong and chemically stable

Glucose units alternate (every second unit unit upside down)

26
Q

what are the advantages of using ethanol as an alternative fuel?

A
  • renewable resource (made from bio mass)
  • burns more cleanly than petroleum (less C & CO)
  • reduces green house gas emissions (plants grown absorb CO2)
  • would create jobs in fermentation process
  • is less toxic than petrol & diesel
27
Q

Disadvantages of using ethanol as an alternative fuel?

A
  • lower heat of combustion than petrol ( less energy produced)
  • large amounts of arable land is required to grow crops ( deforestation, erosion)
  • wouldn’t necessarily be carbon neutral as energy required for distillation & fermentation and transport typically would come from coal
  • engines would need to be modified to tolerate higher concentrations of ethanol
28
Q

what is LDPE?

and how is it produced?

A

Low Density PolyEthlyene

  • It is produced at around 300C
  • 1000-3000atmospheres
  • Uses peroxide as an initiator
29
Q

What is HDPE?

how is it produced?

A

High Density POlyEthylene

  • it is produced at around 60C
  • 10-80 atmospheres
  • using the catalyst: Ziegler-Natta
30
Q

What are the properties of LDPE

A

-it is a newer process than HDPE
-has short alkane branches off the side of the main poymer chain
-this means it is harder for the chains to get close to eachother, meaning it isn’t packed as tightly.
-has weaker dispersion forces
LDPE is therefore:
-more flexible, softer and lower density

31
Q

What are the uses of LDPE?

A

used in:

  • cling wrap
  • plastic bags
  • icecream container lids
32
Q

What are the properties of HDPE?

A
  • has no branched carbon chains, so the polymer can be close together, to create the dispersion forces stronger. This means that HDPE is:
  • a dense, crystaline and rigid polymer
33
Q

What are the uses of HDPE?

A
  • milk bottles
  • chopping boards
  • bins
34
Q

What is PVC ?

A

polyvinyl chloride is made from addition polymerisation reactions involving the monomer VINYL CHLORIDE,
its covalent cl atom means that dispersion forces are strengthened.

35
Q

What are the uses of PVC?

A
  • insulation around electrical cables
  • packaging
  • plumbing pipes
36
Q

What is polystyrene?

A

poly styrene is an addition polymer made from the monomer styrene. Styrene has a very stable benzene ring (C6H5)
-its intermolecular forcers are strong, however these are weakened by benzene ring

37
Q

What are the uses of polystyrene?

A
  • tape and film reels
  • toys
  • CD cases
  • thermal insulation
38
Q

the structure of a LDPE and HDPE

A

has an effect on its intermolecular forces, affecting its properties and uses

39
Q

Why is there research into biopolymers?

A
  • issues with plastics
    1. they are derived from non renewable petroleum
    2. Take centuries to break down in enviro,(accumulating in landfill and enviro, dangerously high levels
40
Q

What is the recent development and use of a named biopolymer?

A
  1. Common name: Biopol
    Systematic name: PHBV (co-polymer made up of 2 different alternating monomers: hyddroxybutyrate & hydroxyvalerate)
  2. Name of bacteria used?
    - Ralstonia Eutrophus
41
Q

What are advantages and disadvantages of

And what is its current use?

What is its potential future developments?

A

Advantages
-properties are similar to polyethylene :
(Strong, insoluble in water, high MP) but is more brittle
-biodegradable
-biocompatible (not rejected by immune system and absorbed safely into body

Disadvantages
-currently very expensive to produce compared to petrochemical plastics

42
Q

What is the production method of PHBV?

A

Production method

  1. Ralstonia eutrophus is cultured in a high glucose enviro (food source)
  2. Bacteria is placed under stress by making these conditions less favourable
  3. Biopolymer is then manufactured under these conditions and stored in the cell wall as granules , a waste product
  4. The bacteria is then dissolved and the polymer is extracted and processed
43
Q

And what is PHBV’s current use?

A

Due to its properties

  • biodegradability: it is used in short term disposable products such as shampoo bottles and eating utensils
  • biocompatibility: medical applications, eg. Stitches (safely and slowly absorbed)

HOWEVER current use of PHBV is limited by high cost of production.
If production costs were cheaper, it would be used in a wider range of applications

44
Q

Potential future developments of PHBV?

A

-gene splicing to transfer the
co-polymer production capability into other bacteria like E.Coli
-scientists are more familiar with E.Coli, therefore easier and cheaper to work with, reducing production costs

  • decreasing crude oil reserves will increase the cost of petrochemical plastics, making PHBV more economically viable
  • potential used is motivated by money*
45
Q

Explain what is meant by a condensation polymer?

A
  • Condensation polymers are made from condensation reactions:
    1. Monomers combine through a reaction of their functional groups
    2. This results in the ejection of a small molecule (often water)

addition polymers produced by petrochemical industry**

-Condensation polymers can be both renewable and biodegradable

46
Q

What are the issues with petrochemical products?

A

Issues:
They are unsustainable in the long term
-polymers (plastics) and fuels are currently provided by petrochem industry
-they are critical in maintaining our standard of living

  1. petrochemicals are non renewable resource ( supply is gradually depleting)
  2. Supply is erratic due to political instability in many countries which produce petrochems
  3. Burning of these petrochemicals have significant consequences on the environment (release of greenhouse gases)
47
Q

What is an alternative resource in place of petrochemicals?

A

Cellulose

  • renewable
  • Is in large quantities (made from biomass)
  • made up of glucose monomers which have basic carbon chain structures
  • these can be converted into short chain alkenes (needed to produce petrochemicals)
48
Q

what is the process of conversion of cellulose to ethylene?

A
  1. cellulose goes to glucose (acid decomposition /bacterial digestion)
  2. glucose is fermented into ethanol
  3. Ethanol is dehydrated into ethylene’
49
Q

Evaluate cellulose as a replacement for petrochemicals?

A

Advantages:

  1. Abundant and easy to produce (biomass)
  2. Renewable resource
  3. contains basic carbon chain structures needed for petrochems
  4. Greenhouse gas emissions are reduced (CO2 absorbed in biomass production)
    - petroleum is non renewable & depleting resource
    - produces potential long term solution to depletion of fossil fuels

Disadvantages:

  1. conversion from cellulose to glucose is caro y slow
  2. energy input is required to farm & process biomass (reduces enviro benefit)
  3. Arable land for food production would be needed instead for polymer & fuel production

Summary: processing of cellulose would become more efficient with further research, petrochemicals will gradually become more expensive as sources deplete

50
Q

An homolgous series with a hydroxyl functional group means?

A

means that alkanols have the ability to form H bonds

, this ability to perform H bonds influences chemical & physical properties of alkanols (liquid at room temp)

51
Q

What do catalysts do?

A

They lower activation energy, reducing the energy needed for reaction

52
Q

Why is ethylene useful?

A
  • can undergo large no. reactions due to reactive double bond (acts as an area of high e- density)
  • which produces a large variety of products
53
Q

What are some useful products of ethylene?

A

ethanol -fuel and solvent
ethylene glycol -antifreeze
polyethylene -plastic

54
Q

What is the main source of ethylene?

A

petroleum (made up of hydrcoarbons of varying lengths

55
Q

What are fractions?

A

hydrocarbons of similar lenghts

56
Q

how does fractional distillation separate fractions of dif. lenths?

A

based on dif boiling points

57
Q

Why do you use cyclohexane and cyclohexene instead of other alkan/enes in the bromine prac?

A

they are both colourless and liquid at room temperature

58
Q

what are 2 ways to limit heatloss from apparatus when comparing heat of combustion of different liquid alkanols

A
  1. Ensure that the flame is close to the base of the water container
  2. The base of the water bath should be made of a material that readily conducts heat, to transfer as much heat from the flame to the water. Furthermore, to limit heat loss, the sides of the container should be made from an insulated material. eg. a copper base container with stainless steel sides.
59
Q

-what are the properties of PVC ?

A

hard, inflexible, brittle polymer

60
Q

what are the properties of polystyrene?

A

crystal polystyrene has high stiffness, good insulation properties

expanded polystyrene has good heat and sound insulation properties (produced by blowing gases through molten polystyrene and allowing it to cool)

61
Q

discuss the need for alternative sources of the compounds presently obtained from petrochemical industry

A
  • petrochemicals are critical in maintining the standard of modern living, yet come from crude oil which is a non-renewable, finite resource
  • for this reason an alternative, renewable/sustainable resource needs to be sourced.

Yr 12 Chemistry (11 decks)

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