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Chemistry CPG > Unit 3: Section 2: Alkanes and Halogenoalkanes > Flashcards

Unit 3: Section 2: Alkanes and Halogenoalkanes Flashcards

1
Q

What is petroleum

A

A mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation

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2
Q

What does saturated mean

A

When an alkane consists of single bonds exclusively

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3
Q

What is the purpose of fractional distillation

A

Separates liquids with different boiling points

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4
Q

What are the 6 fractions in a fractional distillation (in order)

A

Natural gases
Petrol
Naphtha
Kerosene
Diesel
Bitumen

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5
Q

What happens to the physical properties of the hydrocarbon if the carbon chain gets longer

A

Becomes:
- more viscous
- harder to ignite
- less volatile

And has higher boiling points

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6
Q

What does volatile mean

A

How easily a substance will evaporate

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7
Q

What does viscous mean

A

How easy it is to poor a liquid

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8
Q

Why does the physical properties change as the carbon chain of an alkane increases

A

Larger carbon chains have stronger van der Waal’s forces between molecules due to the size of the molecule

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9
Q

Describe the supply and demand of long chain hydrocarbons

A

In high supply and low demand

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10
Q

What are the two methods to converting long chain hydrocarbons into short chain hydrocarbons

A

Catalytic cracking
Thermal cracking

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11
Q

What are the conditions of thermal cracking

A

900 degrees celcius
70 atm
No catalyst

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12
Q

What are the products of thermal cracking

A

Alkenes

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13
Q

What are the conditions of catalytic cracking

A

450 degrees celcius
1-2 atm
Zeolite catalyst

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14
Q

What are the products of catalytic cracking

A

Motor fuels (aromatics, cyclic alkanes, branched alkanes)

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15
Q

What are zeolites made of

A

Aliminum dioxide
Silicon dioxide

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16
Q

What is the use of natural gases

A

Liquified petroleum gas, camping gas

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17
Q

What is the use of Naphtha

A

Processed to make petrochemicals

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18
Q

What are the uses for kerosene

A

Jet fuel, petro chemicals, central heating fuel

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19
Q

What are the uses for diesel

A

Fuel, central heating fuel

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20
Q

What is the use for mineral oil

A

Lubricating oil

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21
Q

What is the use of bitumen

A

Roofing, road surfacing

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22
Q

What products will you get if you burn alkanes with plenty of oxygen

A

Carbon dioxide
Water

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23
Q

What is complete combustion

A

When you oxidise something and you get carbon dioxide and water

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24
Q

What is incomplete combustion

A

Not enough oxygen for complete combustion
So you get carbon (soot) and carbon monoxide instead of or as well as carbon dioxide

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25
Why do you not want carbon monoxide as a product
It's poisonous
26
Why is carbon monoxide posionous
Bind to the same sites on haemoglobin molecules as oxygen molecules do so the body doesn't get enough oxygen
27
What is the general formula for nitrogen oxides
NOx
28
Where and why is nitrogen monoxide produced
In a car engine High pressure and temperature causes the nitrogen and oxygen atoms from the air to react together
29
What is the equation for the formation of nitrogen monoxide
N2(g) + O2(g) -> 2NO(g)
30
What is the equation for the formation of nitrogen dioxide
2NO(g) + O2(g) -> 2NO2(g)
31
What happens to the molecules that don't get burnt in a car engine
Come out as unburnt hydrocarbons Then react with nitrogen oxides in the presence of sunlight to form ground level ozone (O3)
32
What is wrong with ground level ozone
Irritates people's eyes Aggravates respiratory problems Causes lung damage
33
How does sulfur dioxide form
Fossil fuels contain sulfur When they are burnt the sulfur reacts to form sulfur dioxide gas (SO2)
34
What happens if sulfuric acid gets in the atmoshphere
Dissolves in moisture Converted into sulfuric acid
35
What is the problem with acid rain
Destroys trees and vegetation Corrodes buildings and statues Kills fish in lakes
36
Why does burning fossil fuels contribute to global warming
Produces greenhouse gases When they are in the atmosphere they are good at absorbing infrared energy Emit some energy back towards the Earth Increase concentration of greenhouse gases cause the Earth's temperature to increase
37
What do curly arrows show
The movement of a pair of electrons
38
What are the three types of curly arrows
Bond making arrow Bond breaking arrow Bond transfer arrow
39
What is a bond making arrow
When a pair of electrons are attracted to a positive atom
40
What is a bond breaking arrow
An atom is about to have or does have too many bonds so it will break one
41
What is a bond transfer arrow
Happens when a pair of electrons in a bond need to break the bond but cannot do so and form stable products
42
What happens when a halogen reacts with alkanes in photochemical reactions
They form halogenoalkanes
43
What are photochemical reactions
Reactions started by UV light
44
What is a free radical
A free radical is any chemical with an unpaired electron They're very reactive
45
Explain how halogen free radicals can be generated
Mixing halogen with UV light Light gives energy to break the bond - therefore UV light is a condition of the reaction
46
How is CO2 formed
Complete combustion of fuels containing C
47
How is CO formed
Incomplete combustion of fuels containing C
48
How is C (soot) formed
Incomplete combustion of fuels containing C
49
How is H2O formed
Combustion of fuels containing H
50
How is SO2 formed
Combustion of S containing compounds in fuel
51
How is NOx (NO, NO2) formed
Reaction N2 in the air with O2 in the air at very high temperatures (in engines & furnaces)
52
How are unburned hydrocarbons formed
Some of the fuel may not actually burn
53
What are the problems caused by CO2 and what are ways to reduce it
Greenhouse gas Burn less fossil fuels
54
What are the problems caused by CO and what are ways to reduce it
Toxic Ensure a good supply of oxygen when burning fuels
55
What are the problems caused by C (soot) and what are ways to reduce it
Blackens buildings, can cause respiratory problems, global dimming Ensure a good supply of oxygen when burning fuels
56
What are the problems caused by H2O and what are ways to reduce it
Greenhouse gas Burn less fossil fuels
57
What are the problems caused by SO2 and what are ways to reduce it
Acid rain and respiratory problems Remove S from fuel before burning, flue gas desulfurisation
58
What are the problems caused by NOx (NO, NO2) and what are ways to reduce it
Acid rain Use catalytic converters in cars
59
What are the problems caused by unburned hydrocarbons and what are ways to reduce it
Wastes fuel Ensure engines are well-tuned and there is a good supply of oxygen
60
What is the structure of a catalytic converter and how does it lower costs
Has a ceramic light weight honeycomb coated structure with a thin layer of catalytic platinum, to give a large surface area This boosts efficiency and lowers costs of the catalytic converter by reducing the amount of catalyst needed
61
What is the purpose of catalytic converters
Remove CO, NOx and unburned hydrocarbons from the exhaust gases, turning them into CO2, N2 and H2O
61
What is the equation of the conversion that happens in catalytic converters
2CO + 2NO -> 2CO2 + N2
62
What is the equation for when sulfur impurities react with oxygen
S + O2 -> SO2
63
How is acid rain formed
Sulfur impurities when burned can release SO2 SO2 and NO2 will dissolve in clouds and can produce acid rain
64
How is SO2 removed from emmisions
By flue gas desulfirisation The gas is passed through calcium oxide solution which reacts with SO2 and creates an aqueous salt
65
What is the equation for flue gas desulfurisation
SO2 + CaO -> CaSO3
66
What is the equation for when NO2 dissolves in clouds
4NO2(g) + O2(g) +H2O(l) -> 4HNO3(aq)
67
How does CO2 absorb infrared radiation
C=O double bond absorbs infrared radiation IR radiation emitted by the earth and the radiation does not escape
68
How does H2O absorb infrared radiation
O-H single bonds absorb infrared radiation IR radiation emitted by the earth and the radiation does not escape
69
How does CH4 absorb infrared radiation
C-H single bonds absorb infrared radiation IR radiation emitted by the earth and the radiation does not escape
70
What is initiation
When 2 free radicals are formed from 0 free radicals
71
What does intitation require
Requires UV light to break bonds
72
Explain the process of propagation
Has two steps: - When halogen radical reacts with the alkane it will gain a H as they're the element easiest to collide with; this breaks the C-H bond and the C will become the radical - This radical then reacts with more halogen, reforming the halogen in the process
73
What are the equations for the two steps in propogation
Step 1: X (free radical) + Alkane (free radical) -> +HX Step 2: Alkane (free radical) + Halogen -> X (free radical) + Halogenoalkane
74
What is termination
When 2 free radicals collide they will react together and no longer become radicals
75
What is the equation for termination
2FR -> 0FR

Chemistry CPG (10 decks)

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