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Chemistry A-Level > **3.3.2 Alkanes** > Flashcards

**3.3.2 Alkanes** Flashcards

1
Q

Alkane

A
  • Saturated hydrocarbon containing C-H bonds only
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2
Q

Crude oil

A
  • Mixture of diff hydrocarbons
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3
Q

Steps in fractional distillation

A
  • Vapourised + fed to column
  • Rise, cool + condense
  • Products siphoned off
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4
Q

Short carbon chains

A
  • Lower bp, rise higher, collected at top
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5
Q

Long carbon chains

A
  • Higher bp, collected at bottom.
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6
Q

How are hydrocarbons broken down further?

A
  • Cracking
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7
Q

2 types of cracking

A
  • Thermal
  • Catalytic
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8
Q

Why cracking?

A
  • Forms smaller more useful molecules
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9
Q

Thermal cracking produces:

A
  • Alkanes + alkenes
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10
Q

Thermal cracking requires

A
  • 1000℃ + 70atm
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11
Q

Catalytic cracking produces:

A
  • Aromatic compounds w/ c rings
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12
Q

Catalytic cracking requires

A
  • 450℃ + atmospheric pressure
  • ZEOLITE CATALYST
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13
Q

Needed for complete combustion

A
  • Oxygen
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14
Q

Products of complete combustion

A
  • CO2 + H2O
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15
Q

Incomplete combustion

A
  • Not enough oxygen
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16
Q

Products of incomplete combustion

A
  • CO + H2O + C(soot)
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17
Q

Catalytic converter used for

A
  • Remove toxic gases by converting to more stable products
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18
Q

What gases are removed w/ catalytic converter?

A
  • Nitrogenous oxides (NOx)
  • CO
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19
Q

What catalyst is in catalytic converter

A
  • Rhodium
  • Platinum
  • Palladium
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20
Q

What are the products of catalytic converters?

A
  • N2, H2O, CO2
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21
Q

Carbon particulates

A
  • Small fragments of unburned hcarbons
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22
Q

Problems of carbon particulates

A
  • Respiratory problems
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23
Q

Sulfur impurities problems

A
  • Acid rain / acidification of water
  • H2SO4
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24
Q

How can sulfur impurities be removed?

A
  • Flue gas desulfurisation
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25
Q

What is used in flue gas desulfurisation?

A
  • CaO
  • CaCO3
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26
Q

What is needed for production of halogenoalkanes?

A
  • UV light
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27
Q

What are 3 stages of chlorination of alkanes?

A
  • Initiation
  • Propagation
  • Termination
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28
Q

What happens in initiation?

A
  • Halogen broken down
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29
Q

Initiation equation

A
  • Cl2 —> 2Cl* (UV needed)
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30
Q

What happens in propagation?

A
  • H is replaced by Cl* radical reformed as catalyst
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31
Q

Propagation equations

A
  • Cl* + CH4 —> CH3* + HCl
  • CH3* + Cl2 —> CH3Cl + Cl*
32
Q

What happens in termination?

A
  • 2 radicals join to end reaction + form stable product
33
Q

Termination equations

A
  • *CH3 + *CH3 —> C2H6
  • *Cl + *Cl —> Cl2
  • *Cl + *CH3 —> CH3Cl
34
Q

Are alkane bonds polar?

A
  • No, similar electronegativities
35
Q

Alkanes soluble in water?

A
  • No, H bonds in water stronger than alkanes VDWs
36
Q

How reactive alkane?

A
  • Very unreactive
37
Q

What reactions happen w alkanes?

A
  • Combustion
  • Reaction w/ halogens
38
Q

Fractions

A
  • Gases
  • Petrol
  • Kerosene
  • Diesel
  • Lubricating oil
  • Fuel oil
  • Bitumen
39
Q

How does fractional distillation work?

A
  • Crude oil vapourised + entered into fractionating column.
  • Hot bottom, cooler top.
  • HCs have diff boiling points ∴ condense at diff points of fractionating column.
40
Q

What is fracking + how is it done?

A
  • Natural gas in shale rock.
  • Drill into shale + force water + sand into rock to fracture it.
  • Collect gas.
41
Q

During fracking what is added to break up shale + prevent corrosion?

A
  • HCl + methanol.
42
Q

What are 2 pros of fracking?

A
  • Gas supply for years.
  • Reduced imported gas.
43
Q

What are 4 cons of fracking?

A
  • Traffic to local area.
  • Lots of water used.
  • Pollution of water supplies.
  • Can cause small earthquakes.
44
Q

What are the products of cracking alkanes?

A
  • Shorter chain alkane.
  • Alkene.
45
Q

What is the benefit of cracking a long alkane to produce a short alkane?

A
  • More economically valuable as used as fuel.
46
Q

What is the benefit of cracking a long alkane to produce an alkene?

A
  • More reactive.
  • Starting point for many products.
47
Q

What are the conditions of thermal cracking?

A
  • 1000℃.
  • 70 atm.
48
Q

What are the main products of thermal cracking?

A
  • Alkenes.
49
Q

Conditions of catalytic cracking?

A
  • 450℃.
  • Zeolite catalyst (honeycomb structure).
  • Just above 1 atm.
50
Q

3 products of catalytic cracking?

A
  • Cycloalkanes.
  • Aromatic HCs.
  • Branched alkanes.
51
Q

What is a fuel?

A
  • Something which releases heat energy when combusted.
52
Q

What are the products of incomplete combustion in the case of alkanes?

A
  • Carbon monoxide.
  • Carbon.
  • Water.
53
Q

What is the environmental impact of CO?

A
  • Poisonous/ toxic.
54
Q

What is the environmental impact of C?

A
  • Global dimming.
  • Asthma.
  • Cancer.
55
Q

Which type of HCs are most likely to undergo incomplete combustion?

A
  • Longer chain HCs.
56
Q

What is the environmental impact of nitrogen oxides?

A
  • Forms nitric acid –> acid rain.
  • Photochemical smog.
57
Q

What is the environmental impact of Sulphur dioxide/ sulphur impurities?

A
  • Sulphuric acid –> acid rain.
58
Q

What is the environmental impact of unburnt HCs?

A
  • Photochemical smog.
59
Q

What is the environmental impact of CO2?

A
  • Greenhouse gas –> global warming.
60
Q

What is the environmental impact of water vapour?

A
  • Greenhous gas –> global warming.
61
Q

What are flue gases?

A
  • Gases given out by power stations.
62
Q

What are catalytic converters made up of?

A
  • Ceramic honeycomb.
  • Coated in Platinum, palladium + rhodium.
63
Q

What are greenhouse gases?

A
  • Gases which trap infrared radiation + make earth act like greenhouse.
64
Q

What is greenhouse effect?

A
  • Short UV waves enter, reflected as long infrared waves.
  • Greenhouse gases trap infrared, atmosphere heats up.
65
Q

Carbon neutral activities?

A
  • Activities that produce no net CO2 emissions.
66
Q

How are halogenoalkanes formed from alkanes?

A
  • Free radical substitution reactions.
66
Q

What are 3 stages of free radical substitution?

A
  • Initiation, propagation + termination.
67
Q

What happens in initiation?

A
  • Breaking halogen bond to form free radicals.
68
Q

What happens in propagation?

A
  • Products are formed but free radical remains.
69
Q

What happens in termination?

A
  • Free radicals removed, Stable products formed.
70
Q

What is needed for formation of free radical chlorine atom?

A
  • UV light.
71
Q

What is the function of the ozone layer?

A
  • Protects earth from harmful exposure to too many UV rays.
72
Q

How do CFCs break down ozone layer?

A
  • Free radical substitution.
73
Q

Flue gas desulfurization with CaO equation

A
  • CaO(s) + 2H2O(g) + SO2(g) + 1/2O2(g) —> CaSO4.2H2O(s).
74
Q

Flue gas desulfurization with CaCO3 equation

A
  • CaCO3 + 1/2O2(g) + SO2(g) —> CaSO4(s) + CO2(g).

Chemistry A-Level (12 decks)

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