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Chemistry > Topic 5 - Crude Oil > Flashcards

Topic 5 - Crude Oil Flashcards

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1
Q

what is a hydrocarbon?

A
  • molecule that contains ONLY hydrogen and carbon atoms
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2
Q

what is a homologous series?

A

a series of compounds which
- have the same general formula,
- share similar chemical properties,
- neighbouring compounds differ by CH2 units

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3
Q

what are 3 properties of homologous series that change as you go up or down?

A
  • boiling point
    -viscosity
  • ease of ignition
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4
Q

boiling point

A

the LARGER the hydrocarbon, the HIGHER the boiling point
they have more intermolecular forces which require more energy to break

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5
Q

viscosity

A

the LARGER the hydrocarbon, the HIGHER it’s viscosity

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6
Q

ease of ignition

A

the LARGER the hydrocarbon, the HARDER it is to ignite

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7
Q

alkanes

A
  • saturated hydrocarbons
  • each carbon atom bonds to 4 atoms, only covalent bonds
  • formula : CnH2n + 2
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8
Q

alkenes

A
  • unsaturated hydrocarbons
  • they have a double C=C bond, not all carbon atoms form 4 bonds
  • formula : CnH2n
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9
Q

what is crude oil?

A
  • complex mixture of many different hydrocarbons with differing lengths
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10
Q

how is crude oil formed?

A
  • at high temp and pressure
  • from fossilised remains of plants and animals millions of years ago
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11
Q

what is crude oil used for?

A
  • finite resource
  • main source of useful substances and feedstock of petrochemical industry
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12
Q

what are fractions of crude oil?

A

simpler, more useful mixtures than crude oil that contain groups of hydrocarbons of similar lengths

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13
Q

what process is used to separate crude oil into fractions?

A

fractional distillation

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14
Q

fractional distillation

A
  • crude oil is pumped into a fractionating column
  • this has a temp gradient which is hottest at bottom and coldest at top
  • crude oil is heated so most of it evaporates
  • gas rises up the column and gradually condenses at different temperatures
  • explain why similar length condense at same time
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15
Q

order of crude oil fractions from highest to lowest
( R , P , K , D , F , B )

A
  • refinery gas
  • petrol
  • kerosene
  • diesel
  • fuel oil
  • bitumen
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16
Q

refinery gas

A

used for domestic heating appliances and cooking

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17
Q

petrol

A

fuel in cars

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18
Q

kerosene

A

fuel in aircraft

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19
Q

diesel oil

A

fuel in larger vehicles

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20
Q

fuel oil

A

fuel in power stations

21
Q

bitumen

A

used to surface roads
used for roofs of buildings

22
Q

combustion of hydrocarbon

A

hydrocarbon + oxygen -> CO2 + H20

23
Q

when does incomplete combustion of hydrocarbon happen

A

when hydrocarbons are combusted in insufficient oxygen supply

24
Q

what harmful products can incomplete combustion cause?

A
  • soot ( carbon )
  • carbon monoxide
  • sulfur dioxide
  • nitrogen oxides
25
Q

carbon monoxide dangers

A
  • colourless, odourless and toxic gas
  • binds to haemoglobin in blood in RBCs that normally carries O2
  • less oxygen is transported around the body
  • lead to fainting or even death
26
Q

soot dangers

A
  • tiny particles of carbon that deposit as black dust ( soot )
  • makes buildings look dirty
  • reduces air quality and contributes to global dimming : blocks sunlight
  • causes respiratory problems
27
Q

sulfur dioxide

A
  • when fossil fuels are burned, sulphur dioxide can be formed due to sulphur impurities
  • mixes with water in clouds to form sulphuric acid ‘ clouds ‘ which precipitate as acid rain
  • this corrodes metal structures and kills plants and harms ecosystem,
28
Q

nitrogen oxide

A
  • when fuels are burned it releases a lot of energy in the form of heat
  • at the high temp reached in combustion engine, N2 can react with O2 to form nitrogen oxides
  • can cause petrochemical smog and cause acid rain
  • which causes headaches and tiredness
29
Q

advantages of hydrogen as a fuel

A
  • only waste product is water which causes no pollution
  • it is produced from a renewable resource
30
Q

disadvantages of hydrogen as a fuel

A
  • special, expensive engine required to use hydrogen as a fuel
  • hydrogen very flammable so hard to store safely
31
Q

what is cracking?

A

breaking down larger, saturated hydrocarbons into smaller hydrocarbons (some are unsaturated alkenes )

32
Q

why do we use cracking?

A
  • short chain hydrocarbons are more useful because they are more flammable, so ignite more easily
  • this makes them more useful as fuels
33
Q

two conditions needed for cracking?

A
  • catalysts
  • high temperatures ( 400 - 700 )
34
Q

which gases formed the early atmosphere?

A
  • gases released from intense volcanic activity
35
Q

what gases were in the early atmosphere?

A
  • mostly carbon dioxide
  • small amounts of other gases
    ( nitrogen, water vapour and methane )
  • little or no oxygen
36
Q

composition of today’s atmosphere

A

Nitrogen: About 78%
Oxygen: About 21%
Carbon dioxide: About 0.042%

37
Q

how did the amount of carbon dioxide decrease:

A
  • absorption of oceans
  • absorption by plants and algae
38
Q

formation of oceans

A
  • as the Earth cooled down
  • water vapour condensed forming the oceans
39
Q

absorption of CO2 by oceans

A
  • when the oceans formed, CO2 from atmosphere dissolved into them
  • dissolved CO2 formed carbonate precipitates
40
Q

absorption of CO2 by oceans ( p2 )

A
  • when marine animals evolved , their skeletons contained carbonates from oceans
  • when they died, they formed sedimentary rocks such as limestone
  • locked CO2 away
41
Q

absorption by plants and algae

A

algae and green plants absorbed CO2 in the atmosphere and used it in photosynthesis to make glucose

42
Q

increasing amount of oxygen

A
  • algae and green plants produced oxygen by photosynthesis
  • oxygen created the ozone layer (O3) that blocked harmful rays from Sun
  • allowing more complex organisms to evolve
43
Q

test for oxygen

A
  • put a glowing splint near a test tube containing gas
  • if it is oxygen, the splint will relight
44
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48
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Chemistry (13 decks)

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