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Chemistry > 4(b) Crude oil > Flashcards

4(b) Crude oil Flashcards

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1
Q

crude oil?

A

as a mixture, it isn’t a very useful substance

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2
Q

fractions?

A

different hydrocarbons: each consists of groups of hydrocarbons of similar length

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3
Q

fractional distillation?

A

molecules in each fraction have similar properties and boiling points so they can be separated in a fractional column.

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4
Q

what does the boiling and melting point of each fraction depend on?

A

the number of carbon atoms in the chain
size + length determines which fraction it will be separated into
most fractions contain many alkanes –> compounds C with a single bond

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5
Q

fractional column temperature gradient?

A

very hot (bottom) and cool (top)

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6
Q

how does a fractioning column work?

A

crude oil enters the column
- crude oil heated so it will rise

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7
Q

what happens to the hydrocarbons that have a low boiling point, in a fractional column?

A
  • vapors of hydrocarbons with very high boiling points will immediately condense into liquid at the higher temps lower down tapped off at the bottom of the column
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8
Q

what happens to the hydrocarbons that have a high boiling point, in a fractional column?

A

vapours of hydrocarbons with low boiling points will rise

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9
Q

where are smaller and bigger hydrocarbons collected?

A
  • smaller is at the top (some as gases)
  • bigger at the lower sections
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10
Q

main properties of the main fractions of crude oil? (how to know the difference)

A
  • viscosity
  • colour
  • melting/ boiling point
  • volatility
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11
Q

viscosity?

A

ease of liquid flow (large viscosity - thick and flows less easily)

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12
Q

factors that affect the viscosity of crude oil?

A
  • if no of carbon atoms is high, the attraction between the hydrocarbon molecules also increases
  • results in the liquid becoming more viscous with increasing length of chain (flow less easy)
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13
Q

factors that affect the colour of crude oil?

A

as C chain length increases the color of the liquid gets darker as it gets thicker and more viscous

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14
Q

factors that affect the melting/boling point of crude oil?

A

as molecules get larger, intermolecular attractions become greater:
- more heat needed to separate the molecules
- increase molecular size. greater boiling point.

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15
Q

volatility?

A

tendency of a substance to vaporise

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16
Q

factors affecting volatility?

A

increase molecular size, hydrocarbon liquids become less volatile, due to the attraction between the molecules increasing with increasing molecular size

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17
Q

what are the different fractions?

A

refinery gases (1-4), gasoline (4-12), kerosene (12-16), diesel (14-18), fuel oil (19-25) and bitumen (more than 70)

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18
Q

uses of refinery gases?

A

domestic heating and cooking

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19
Q

uses of gasoline?

A

fuel for cars

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20
Q

uses of kerosene?

A

jet fuel

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21
Q

diesel uses?

A

diesel engines

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22
Q

heavy fuel oil uses?

A

ship and power stations

23
Q

bitumen uses?

A

surfacing roads and roofs

24
Q

how to remember to order of the fractions?

A

Red Grandmas plant Kangaroos Dung Happily Farting On Bugs

25
Q

what composes fossil fuels?

A

coal, oil, natural gas, oil shales and tar sands

26
Q

what does combustion of fossil fuels contribute too?

A

source of atmospheric polution

27
Q

How are fossil fuels obtained?

A

non-renewable fossil fuels are obtained from crude oil by fractional distilation

28
Q

what do all these fuels contain?

A

carbon, hydrogen and a small amount of sulfur

29
Q

products of combustion?

A
  • releases:
    • CO2
    • CO
    • oxides of Nitrogen and sulfur
30
Q

products of incomplete combustion?

A

in addition incomplete combustion of fuels gives rise to unburned hydrocarbon and carbon particles

31
Q

what is a fuel?

A

it is a substance which releases energy in an exothermic reaction

32
Q

products of combustion of fossil fuels

A

water and carbon dioxide

33
Q

when does incomplete combustion occur?

A

when there is insufficient O2 to burn

34
Q

products of incomplete combustion?

A

unburnt fuel (soot), CO and water

35
Q

what is CO?

A
  • toxic and odorless gas which can cause dizziness, loss of onerousness and eventually death
36
Q

what does CO do to the body?

A

it binds well to hemoglobin which therefore cannot bind oxygen and carbon dioxide for gas exchange

37
Q

how are nitrogen oxides (NO and NO2) formed?

A

when nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines (car engines) and blast furnaces.

38
Q

How are nitrogen oxides dangerous?

A

In the atmosphere, nitrogen oxides can combine with water to
produce nitric acid (HNO3)

39
Q

effects of nitric acid?

A

acid rain with similar effects as SO2 as well as producing photochemical smog and breathing difficulties in particular for people suffering from asthma

40
Q

catalyst converters use?

A

designed to reduce the polluting gases produced in car exhausts

41
Q

sources of sulfur dioxide?

A

combustion of fossil fuels - especially coal.
fossil fuels are often contaminated with small amounts of sulfur impurities so when combusted the fuels get oxidized to sulfur dioxide.

42
Q

effects of sulfur dioxide?

A
  • acid rain (dissolves in rainwater droplets to from sulfuric acid)
43
Q

affects of acid rain?

A
  • causes corrosion to metal buildings and statues made of carbonate rock
  • damage to aquatic animals
  • pollute crops and water supplies
  • irritates lungs, throats and eyes
44
Q

saturated molecules?

A

Contain single bonds only

45
Q

unsaturated molecules?

A

contain double bonds between carbon atoms (alkenes)

46
Q

cracking?

A

the process of converting long chain alkane molecules (further processing) into short chain molecules (more useful)

47
Q

2 methods of cracking?

A
  • catalyst cracking
  • steam cracking
48
Q

process of catalyst cracking?

A
  • heat the hydrocarbon molecules to around 600-700 degrees to vaporize them
  • the vapor passes over a hot powered catalyst of aluminum oxide
  • process break covalent bonds in the molecules as they come into contact with the surface of the catalyst (causing thermal decomposition reactions)
49
Q

in what way are hydrocarbons broken down using catalyst cracking?

A

in a random way which produces a mixture of smaller alkanes and alkenes

50
Q

supply?

A

how much of a particular fraction can be produced from refining the crude oil

51
Q

demand?

A

how much customers want to buy

52
Q

why is cracking necessary?

A

because generally the demand outstrips the supply and cracking converts surplus unwanted fractions into more useful ones

53
Q

is cracking endo or exo?

A

endothermic reaction

Chemistry (22 decks)

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