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
What is used in flue gas desulfurisation?
- CaO - CaCO3
26
What is needed for production of halogenoalkanes?
- UV light
27
What are 3 stages of chlorination of alkanes?
- Initiation - Propagation - Termination
28
What happens in initiation?
- Halogen broken down
29
Initiation equation
- Cl2 ---> 2Cl* (UV needed)
30
What happens in propagation?
- H is replaced by Cl* radical reformed as catalyst
31
Propagation equations
- Cl* + CH4 ---> CH3* + HCl - CH3* + Cl2 ---> CH3Cl + Cl*
32
What happens in termination?
- 2 radicals join to end reaction + form stable product
33
Termination equations
- *CH3 + *CH3 ---> C2H6 - *Cl + *Cl ---> Cl2 - *Cl + *CH3 ---> CH3Cl
34
Are alkane bonds polar?
- No, similar electronegativities
35
Alkanes soluble in water?
- No, H bonds in water stronger than alkanes VDWs
36
How reactive alkane?
- Very unreactive
37
What reactions happen w alkanes?
- Combustion - Reaction w/ halogens
38
Fractions
- Gases - Petrol - Kerosene - Diesel - Lubricating oil - Fuel oil - Bitumen
39
How does fractional distillation work?
- Crude oil vapourised + entered into fractionating column. - Hot bottom, cooler top. - HCs have diff boiling points ∴ condense at diff points of fractionating column.
40
What is fracking + how is it done?
- Natural gas in shale rock. - Drill into shale + force water + sand into rock to fracture it. - Collect gas.
41
During fracking what is added to break up shale + prevent corrosion?
- HCl + methanol.
42
What are 2 pros of fracking?
- Gas supply for years. - Reduced imported gas.
43
What are 4 cons of fracking?
- Traffic to local area. - Lots of water used. - Pollution of water supplies. - Can cause small earthquakes.
44
What are the products of cracking alkanes?
- Shorter chain alkane. - Alkene.
45
What is the benefit of cracking a long alkane to produce a short alkane?
- More economically valuable as used as fuel.
46
What is the benefit of cracking a long alkane to produce an alkene?
- More reactive. - Starting point for many products.
47
What are the conditions of thermal cracking?
- 1000℃. - 70 atm.
48
What are the main products of thermal cracking?
- Alkenes.
49
Conditions of catalytic cracking?
- 450℃. - Zeolite catalyst (honeycomb structure). - Just above 1 atm.
50
3 products of catalytic cracking?
- Cycloalkanes. - Aromatic HCs. - Branched alkanes.
51
What is a fuel?
- Something which releases heat energy when combusted.
52
What are the products of incomplete combustion in the case of alkanes?
- Carbon monoxide. - Carbon. - Water.
53
What is the environmental impact of CO?
- Poisonous/ toxic.
54
What is the environmental impact of C?
- Global dimming. - Asthma. - Cancer.
55
Which type of HCs are most likely to undergo incomplete combustion?
- Longer chain HCs.
56
What is the environmental impact of nitrogen oxides?
- Forms nitric acid --> acid rain. - Photochemical smog.
57
What is the environmental impact of Sulphur dioxide/ sulphur impurities?
- Sulphuric acid --> acid rain.
58
What is the environmental impact of unburnt HCs?
- Photochemical smog.
59
What is the environmental impact of CO2?
- Greenhouse gas --> global warming.
60
What is the environmental impact of water vapour?
- Greenhous gas --> global warming.
61
What are flue gases?
- Gases given out by power stations.
62
What are catalytic converters made up of?
- Ceramic honeycomb. - Coated in Platinum, palladium + rhodium.
63
What are greenhouse gases?
- Gases which trap infrared radiation + make earth act like greenhouse.
64
What is greenhouse effect?
- Short UV waves enter, reflected as long infrared waves. - Greenhouse gases trap infrared, atmosphere heats up.
65
Carbon neutral activities?
- Activities that produce no net CO2 emissions.
66
How are halogenoalkanes formed from alkanes?
- Free radical substitution reactions.
66
What are 3 stages of free radical substitution?
- Initiation, propagation + termination.
67
What happens in initiation?
- Breaking halogen bond to form free radicals.
68
What happens in propagation?
- Products are formed but free radical remains.
69
What happens in termination?
- Free radicals removed, Stable products formed.
70
What is needed for formation of free radical chlorine atom?
- UV light.
71
What is the function of the ozone layer?
- Protects earth from harmful exposure to too many UV rays.
72
How do CFCs break down ozone layer?
- Free radical substitution.
73
Flue gas desulfurization with CaO equation
- CaO(s) + 2H2O(g) + SO2(g) + 1/2O2(g) —> CaSO4.2H2O(s).
74
Flue gas desulfurization with CaCO3 equation
- CaCO3 + 1/2O2(g) + SO2(g) —> CaSO4(s) + CO2(g).