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A level Chemistry > Unit 2.5 - Hydrocarbons > Flashcards

Unit 2.5 - Hydrocarbons Flashcards

1
Q

Give 2 examples of types of hydrocarbons and explain why they are hydrocarbons

A

Alkanes and alkenes
Contain hydrogen and carbon only

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2
Q

What type of hydrocarbons are alkanes and alkenes?

A

Aliphatic hydrocarbons

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3
Q

Aliphatic hydrocarbons

A

Straight chain

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4
Q

What do alkanes and alkenes contain that makes them aliphatic (straight chain) hydrocarbons?

A

Carbon chains with C-C bonds

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5
Q

Which is saturated - alkanes or alkenes? Why?

A

Alkanes are saturated (only form single covalent bonds, C-C and C-H)

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6
Q

Are alkanes or alkenes unsaturated and why?

A

Alkenes are unsaturated
Have 1 C=C bond

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7
Q

What’s the main source of alkanes?

A

Crude oil and natural gas

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8
Q

What are alkanes primarily used as?

A

Fuels

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9
Q

What’s another word for crude oil?

A

Petroleum

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10
Q

What IS crude oil?

A

A complex mixture of saturated hydrocarbons, mainly alkanes

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11
Q

Describe how crude oil is formed

A

Formed from the remains of marine animals that lived many years ago…
Over time, they died
Sank to the bottom of the sea
Got covered in mud
The remain were compressed over time until they turned into a liquid
Collected in porous rocks like sandstone

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12
Q

How do we extract crude oil?

A

We require powerful oil rigs

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13
Q

What is the purpose of fractional distillation?

A

The first step in the separation of the different hydrocarbons in petroleum

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14
Q

What does fractional distillation separate substances according to?

A

According to their different boiling points

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15
Q

What’s the first step of fractional distillation?

A

Heated petroleum passed into a distillation column

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16
Q

Describe the hydrocarbons that collect at the top of the chamber during fractional distilllation

A

Low melting points
Short chain
More volatile (easily evaporated at normal temperatures)

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17
Q

Which hydrocarbons following fractional distillation are most in demand? Why?

A

The ones that collect at the top of the column (short chain)
Low melting point and more volatile

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18
Q

Place, in order, the different hydrocarbons that wold be extracted from crude oil upon fractional distillation

A

Gases
Gasoline
Naphtha
Kerosine
Gas oil
Residue

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19
Q

Example of a gas extracted from crude oil

A

Methane

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20
Q

What is gasoline?

A

Petrol

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21
Q

What is naphtha?

A

Chemical feedstock

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22
Q

Give 2 uses of kerosine

A

Jet fuel
Heating fuel

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23
Q

What is gas oil used as?

A

Diesel

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24
Q

Give 3 examples of residue from the fractional distillation of crude oil

A

Lubricating oil
Waxes
Bitumen

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25
Q

What is most of the product of the fractional distillation of crude oil?

A

Residue

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26
Q

Fractions

A

Mixtures of hydrocarbons of similar chain length and thus similar boiling points

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27
Q

Wha temperatures do fractions boil in the range of?

A

40 to 500 degrees Celsius

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28
Q

2 advantages of petrolium/crude oil

A

An important chemical feedstock to the chemical industry
(Many chemicals come from it and are used to prepare other organic compounds)
Relied on for the economy (used in cars and central heating systems)

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29
Q

2 disadvantages of crude oil/petroleum

A

Releases greenhouse gases
Is non-renewable

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30
Q

What type of bonds are the C-C and C-H bonds in alkanes?

A

Non-polar covalent bonds

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31
Q

What type of molecules are alkanes?

A

Non-polar

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32
Q

What type of forces are between alkane molecules?

A

Weak Van der Waal forces

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33
Q

Describe the melting and boiling points of alkanes

A

Low

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34
Q

What are alkanes soluble in? Why?

A

Non-polar solvents such as other hydrocarbons
(They’re non polar, and like dissolves with like)

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35
Q

What are alkanes insoluble in? Why?

A

Polar solvents like water
(Alkanes are non polar and like dissolves with like)

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36
Q

Are alkanes chemically reactive or unreactive? Why?

A

Unreactive
Strength of the C-C and C-H bonds

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37
Q

Which processes do alkanes undergo?

A
  1. Combustion
  2. Cracking - homolytic fission of the C-C bond
  3. Photo chlorination - radical attack
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38
Q

What is a combustion reaction?

A

Reaction with oxygen

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39
Q

Draw a diagram of the apparatus that you would use for the identification of the products of the combustion of a hydrocarbon

A

(See notes)

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40
Q

What are 2 things you’d use to identify the products of the combustion of a hydrocarbon?

A

Cobalt chloride paper
Limewater

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41
Q

What does cobalt chloride paper do?

A

Test for the presence of water

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42
Q

What would a positive test of a cobalt chloride paper show and what would this represent?

A

Blue to pink
Water is present

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43
Q

What would a positive test in limewater be and what would this represent?

A

Turns cloudy
CO2 is present

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44
Q

What colour flame do alkanes burn with?

A

Yellow

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45
Q

Do alkanes burn with a lot or a small amount of smoke?

A

Little or no smoke

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46
Q

What are most fossil fuels that are burnt to provide energy?

A

Alkanes

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47
Q

Give some examples of fossil fuels burnt to provide energy that are alkanes

A

Natural gas (methane)
L.P.G (propane and butane)
Petrol
Diesel
Power station oil
Marine fuel

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48
Q

What has the combustion of alkanes contributed to?

A

The greenhouse effect
Acid rain
Photochemical smog

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49
Q

How has the combustion of alkane contributed to acid rain?

A

Combusting impurities in the fuels

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50
Q

Why are alternative fuels being sought from alkanes?

A

They contribute to things like the greenhouse effect, acid rain and photochemical smog

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51
Q

When would an alkane undergo incomplete combustion?

A

In a lack of oxygen

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52
Q

What does the incomplete combustion of an alkane produce?

A

Carbon monoxide (CO)

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53
Q

What’s the problem with carbon monoxide?

A

Highly toxic

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54
Q

Why is carbon monoxide toxic?

A

Binds to haemoglobin, effecting gas exchange

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55
Q

Why is it important to keep stoves in good condition?

A

So that they have enough oxygen so that incomplete combustion doesn’t occur and form carbon monoxide

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56
Q

Products of incomplete combustion

A

Carbon monoxide (CO)
Water (often present as steam - use state symbol ‘g’)

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57
Q

In what form is the water produced from combustion?

A

Often as steam
(Use state symbol ‘g’)

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58
Q

What is cracking?

A

The process where large, less useful hydrocarbon molecules are broken down into smaller, more useful molecules

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59
Q

What will the useful molecules of cracking be?

A

A mixture of saturated and unsaturated hydrocarbons

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60
Q

Why are smaller molecules from cracking more useful than larger ones?

A

They burn easier

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61
Q

Why do smaller molecules burn easier? What does this make them?

A

Lower boiling temperature = evaporate better, and it’s the vapour of a fuel that burns
= better fuels

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62
Q

What is an alternative thing that can occur during cracking?

A

Straight chain alkanes are converted into branched alkanes

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63
Q

What is one of the main fractions cracked?

A

Naphtha

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64
Q

What conditions are required for cracking?

A

Very high temperatures and pressure

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65
Q

How is naphtha cracked?

A

Feedstock is heated to around 800 degrees Celsius (very high temperature and pressure)
Steam is added to dilute the feedstock

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66
Q

What are some fractions obtained from naphtha?

A

Methane
Ethene
Propene
Petrol
Other alkenes

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67
Q

What does cracking always form?

A

A smaller chain hydrocarbon and an alkene

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68
Q

What does cracking involve the formation of?

A

Free radicals

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69
Q

Why does cracking involve the formation of free radicals?

A

The C-C bond is broken at the high temperatures used

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70
Q

What has happened to the C-C bond in a hydrocarbon when it’s been broken at the high temperatures of cracking?

A

The homolysis of the C-C bod

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71
Q

When does the homolysis of the C-C bond in a hydrocarbon occur?

A

When the C-C bond is broken at the high temperatures used

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72
Q

What are the 2 ways that covalent bonds in organic compounds can break?

A

Homolytic bond fission
Heterolytic bond fission

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73
Q

What are homolytic and heterolytic bond fission examples of?

A

Ways that the covalent bonds in organic compounds can break

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74
Q

Homolytic bond fission

A

The covalent bonds break in such a way that each atom forming the bond retains one electron

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75
Q

What is the species formed from homolytic bond fission and why?

A

A free radical (has an unpaired electron)

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76
Q

Describe free radicals

A

Very reactive

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77
Q

Describe and give examples of reactions involving free radicals

A

Very rapid
E.g - photo chlorination of methane and cracking

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78
Q

Heterolytic bond fission

A

The covalent bonds break in such a way that one atom takes both electrons in the bond

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79
Q

What’s the most common type of bond fission?

A

Heterolytic bond fission

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80
Q

How are reactions involving heterolytic bond fission different to those involving homolytic bond fission?

A

Much slower

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81
Q

What does heterolytic bond fission form?

A

An electrophile and a nucleophile

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82
Q

Fission

A

The breaking of a chemical bond

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83
Q

What type of property is boiling point?

A

Physical

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84
Q

What physical property of molecules is used to separate them during fractional distillation?

A

Boiling points

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85
Q

What does methane react with and how?

A

Chlorine, vigorously

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86
Q

Under which conditions does methane react vigorously with chlorine

A

In sunlight (UV light)

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87
Q

Under which conditions would methane not react with chlorine? Why?

A

In the dark
The photo chlorination of methane required UV light

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88
Q

What’s the name for methane reacting with chlorine?

A

Photo chlorination of methane

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89
Q

What type of reaction is the photo chlorination of methane?

A

Free radical substitution

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90
Q

Write the reaction to form chloromethane

A

CH4 + Cl2 —> CH3Cl + HCl

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91
Q

Write the reaction to form dichloromethane

A

CH3Cl + Cl2 —> CH2Cl2 + HCl

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92
Q

What can also be formed in the photo chlorination of methane as well as chloromethane and dichloromethane and how?

A

Trichloroethane and tetrachloromethane
The products of the reaction before can react with further chlorine molecules

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93
Q

Why is the photo chlorination of methane a free radical substitution reaction?

A

Hydrogen atoms in the alkanes are substituted for chlorine atoms

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94
Q

What are the three steps to a free radical substitution reaction?

A

Initiation
Propagation
Termination

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95
Q

What happens during the initiation stage for free radical substation during the photo chlorination of methane?

A

Chlorine molecules in UV light undergo homolytic fissio
Forms free radicals

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96
Q

How much energy is required for the formation of free radicals during the initiation stage of free radical substation for the photo chlorination of methane?

A

A considerable amount - equivalent to the bond enthalpy of chlorine molecules

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97
Q

What type of reaction is initiation during free radical substitution?

A

Endothermic

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98
Q

Write the equation for the initiation stage of the free radical substitution reaction during the photo chlorination of methane

A

Cl2 —> 2Cl•

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99
Q

What happens during the propagation stage for free radical substation during the photo chlorination of methane?

A

Involves the formation of products
Chlorine radicals reform in the course of the reaction and are able to react with more methane molecules

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100
Q

Describe the propagation stage (2 separate things) of free radical substitution. Why is this?

A

Very fast due to the presence of free radicals
Self-sustaining due to chlorine radicals reforming in the course of the reaction that are able to react with more methane molecules

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101
Q

Why is the propagation stage of the photo chlorination of methane self-sustaining?

A

Chlorine radicals reform in the course of the reaction and so are able to react with more methane molecules

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102
Q

What type of reaction is the propagation stage of free radical substitution?

A

Chain reaction

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103
Q

What does the fact that the propagation stage of free radical substitution is a chain reaction mean for it?

A

One chlorine radical can react with many thousand methane molecules in a fraction of a second

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104
Q

Write the equations for the formation of chloromethane

A

CH4 + Cl• —> CH3 • + HCl
CH3 • + Cl —> CH2Cl2 + Cl •

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105
Q

Write the equations for the formation of dichloromethane

A

CH3Cl + Cl • —> CH2Cl • + HCl
CH2Cl • + Cl2 —> CH2Cl2 + Cl •

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106
Q

What happens during the termination stage for free radical substation during the photo chlorination of methane?

A

All remaining free radicals combine and are destructed

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107
Q

Where do the remaining free radicals usually combine at the termination stage of free radical substitution?

A

On the walls of the reaction vessel

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108
Q

What does the termination stage of free radical substitution produce?

A

Stable products that are organic molecules

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109
Q

Show free radicals combining to form ethane

A

CH3 • + CH3 • —> CH3CH3

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110
Q

What do we need to be able to apply to multiple alkanes?

A

The reaction mechanism s for their photo chlorination reactions

111
Q

What type of bonds do alkanes have?

A

C-C bonds and a single C=C bond

112
Q

How many C=C bonds to alkenes have?

A

1

113
Q

What word describes alkenes?

A

Unsaturated

114
Q

What is the position of the double bond in alkenes initiated with?

A

A number

115
Q

What does the number in the name of an alkene initiate?

A

The position of a double bond

116
Q

Which alkenes does the numbering of the position of the double bond not apply for?

A

Ethene
Propene

117
Q

Draw and label the structure of Ethene

A

(See notes)

118
Q

What shape is an Ethene molecule?

A

Trigonal planar

119
Q

What size bond angles does Ethene have?

A

120 degrees

120
Q

What are the 2 types of bond that the double bond in Ethene contains?

A

Sigma bond
Pi bond

121
Q

What’s a sigma bond?

A

A covalent bond formed by the direct overlap of orbitals (s and p)

122
Q

What’s a pi bond?

A

Formed by the sideways overlap of 2 Px orbitals, with the electrons above and below the plane of the 2 carbon atoms

123
Q

What can the pi bond be thought of as?

A

A negative charge cloud above and below the plane of the molecule

124
Q

Which bond is weakest - the pi bond or the sigma bond?

A

Pi bond

125
Q

Which bond is most reactive - the pi bond or the sigma bond?

A

The pi bond

126
Q

What’s the region of negative charge in a molecule of Ethene?

A

The pi bond

127
Q

Which part of an Ethene molecule attracts electrophils and why?

A

The pi bond as this is the region of negative charge

128
Q

What does the pi bond of Ethene attract? Why?

A

Electrophils, as electrophils are positively charges and the pi bond is the region of negative charge

129
Q

What do alkenes react through?

A

Electrophillic addition

130
Q

Which part of an Ethene molecule takes part in reactions?

A

The pi electrons

131
Q

Which part of Ethene seeks electrophiles and why?

A

The pi electrons as they’re negatively charged

132
Q

What do pi bonds seek?

A

Electrophiles

133
Q

How are alkenes prepared from halogenoalkanes?

A

Using elimination reactions

134
Q

How can Ethene be prepared from bromoethane?

A

By the elimination of HBr

135
Q

How is Ethene prepared from bromoethane by the elimination of HBr?

A

Bromoethane is refluxed with sodium hydroxide in ethanol

136
Q

What are the most important reactions that Ethene undergoes?

A

Addition reactions

137
Q

Which bond is broken during the addition reactions of Ethene?

A

Pi bond

138
Q

What happens after the pi bond has broken in Ethene in its addition reactions?

A

Atoms or groups add onto the 2 carbon atoms in the double bond

139
Q

Why is only one product available in the addition reactions of Ethene?

A

Its symmetry

140
Q

How come Ethene is symmetrical?

A

It’s only made up of 2 atoms

141
Q

List all of the addition reactions of Ethene

A

Catalytic hydrogenation (reduction)
Addition of bromine
Decolorisation of potassium manganate (VII)
Addition of hydrogen bromide
Addition of water

142
Q

What is catalytic hydrogenation also known as and why?

A

Reduction
Gain of hydrogen

143
Q

Write the equation for the catalytic hydrogenation of Ethene

A

CH2=CH2 + H2 —> CH3CH3

144
Q

What does hydrogenation involve the addition of?

A

Hydrogen

145
Q

What turns into what during hydrogenation?

A

Alkene into an alkane

146
Q

What brings about the conversion of Ethene to ethane during its catalytic hydrogenation?

A

A nickel catalyst

147
Q

At what termparture is Ethene converted into ethane during catalytic hydrogenation?

A

About 150 degrees Celsius

148
Q

Which reaction does the production of margarine use and why?

A

Catalytic hydrogenation
Unsaturated oils are hardened by the conversion into saturated products

149
Q

The production of what uses the process of catalytic hydrogenation?

A

Margarine

150
Q

What type of reaction do alkenes undergo with halogens such as chlorine and bromine?

A

Electrophilic addition

151
Q

What do alkenes undergo electrophilic addition reactions with?

A

Halogens such as chlorine and bromine

152
Q

Under which conditions do alkenes undergo electrophilic addition reactions with halogens such as chlorine and bromine?

A

Room temperature

153
Q

What type of bromine is used when reacting with alkenes?

A

Aqueous bromine water

154
Q

What happens to bromine water when reacted with an alkene?

A

It’s decolorised
Turns from orange to colourless

155
Q

What’s the colour change that makes bromine water become decolourised in an alkene?

A

Orange to colourless

156
Q

Which 2 reactions are used to test for the presence of a C=C double bond?

A

Decolorisation of bromine water
Decolorisation of potassium manganate (VII)

157
Q

What do both the decolorisation of bromine water and potassium manganate test for?

A

The presence of the C=C double bond

158
Q

Write the equation for bromine water reacting with Ethene

A

CH2=CH2 + Br2 —> CH2BrCH2Br

159
Q

Where is bromine added to Ethene when it reacts?

A

Across the 2 carbon atoms in the double bond

160
Q

What’s the decolorisation that occurs with an alkene and potassium manganate (VII) in the presence of a C=C double bond?

A

Purple —> colourless

161
Q

At what temperature does an addition of hydrogen bromide to an alkene occur at?

A

Room temperature

162
Q

What’s used as a reagent in the addition of hydrogen bromide to an alkene?

A

Hydrobromic acid

163
Q

Write the equation for hydrogen bromide reacting with Ethene

A

CH2=CH2 + HBr —> CH3CH2Br

164
Q

How is ethanol produced industrially?

A

By the direct addition of water (as steam) to Ethene

165
Q

What is produced by doing water (steam) to Ethene?

A

Ethanol

166
Q

In what form i water added to Ethene to reduce ethanol?

A

Steam

167
Q

Write the equation for water being added to ethene to produce ethanol

A

CH2=CH2 + H2O —> CH3CH2OH

168
Q

What are the conditions for the addition of water to ethene?

A

Phosphoric acid catalyst/concentrated sulphuric acid
300 degrees
60 atm pressure

169
Q

Catalyst for the addition of water to ethene

A

Phosphoric acid
OR
Concentrated sulfuric acid

170
Q

Temperature for the reaction of addition of water to ethene

A

300 degrees

171
Q

Pressure for the addition of water to ethene reaction

A

60 atm

172
Q

How is Propene different to ethene?

A

Asymmetrical

173
Q

Reagent, conditions and observations for the addition of bromine to Propene - what is the significance of these?

A

Bromine water
Room temperature
Decolorised bromine water (orange to colourless)
All the same as bromine with ethene

174
Q

How many products form with the addition of bromine to Propene?

A

1 (same as ethene)

175
Q

What is the addition of bromine to Propene an example of and why?

A

Electrophillic addition
Bromine acts as an electrophile

176
Q

Equation for the reaction of Propene with bromine

A

CH3CH=CH2 + Br2 —> CH3CHBrCH2Br

177
Q

What is the reaction of Propene with hydrogen bromide an example of?

A

Electrophillic addition

178
Q

What does the fact that Propene is asymmetrical mean for it in a particular circumstance?

A

2 organic products can be formed in the addition reaction between Propene and hydrogen bromide

179
Q

How many products would form in the reaction of an alkene with hydrogen bromide if it were symmetrical?

A

1

180
Q

Conditions for the reaction of hydrogen bromide with Propene

A

Room temperature (same as with ethene)

181
Q

Whats’t the reagent for the reaction between Propene and hydrogenbromide?

A

Aqueous solution of hydrogen bromide

182
Q

2-bromopropane

A

CH3CHBrCH3

183
Q

1-bromopropane

A

CH3CH2CH2Br

184
Q

What’s the major product of the reaction of Propene with hydrogen bromide?

A

2-bromopropane

185
Q

What’s the minor product for the reaction between hydrogen bromide and Propene?

A

1-bromopropane

186
Q

What does it mean that 2-bromopropane is the major product of the reaction between Propene and hydrogen bromide?

A

Only a small amount of other product forms

187
Q

Write the equation for the first step for the electrophilic addition of hydrogen bromide to Propene

A

CH3CH=CH2 + H+ —> CH3CH+CH3

188
Q

What’s the equation for the second step of the Electrophillic addition of hydrogen bromide to Propene?

A

CH3CH+CH3 + Br- —> CH3CHBrCH3

189
Q

What does a Curley arrow represent?

A

The movement of a pair of electrons, from negative to positive

190
Q

In which direction does a pair of electrons always move to and from?

A

From negative to positive

191
Q

What’s the electrophile in the electrophilic addition of hydrogen bromide to Propene?

A

The hydrogen ion, H+

192
Q

What’s the source of electrons in the electrphillic addition of hydrogen bromide to Propene?

A

Pi bond

193
Q

Why is the pi bond the source of electrons in the Electrophillic addition of hydrogen bromide to Propene?

A

A region of high electron density

194
Q

Describe with the aid of diagrams the Electrophillic addition of hydrogen bromide to Propene

A

As the hydrogen ion approaches the C=C bond, the pi Bon begins to break
A new bond is formed between the carbon atom and the hydrogen
An intermediate is formed - a carbocation
The carbocation is a reactive species, and a bromide ion combines with it (has a lone pair of electrons) to give the final product

(See diagrams in notes)

195
Q

What’s the name of the intermediate formed in the Electrophilic addition of hydrogen bromide to Propene?

A

Carbocatalyst

196
Q

Why is 2-bromopropane the major product of the reaction between hydrogen bromide and Propene?

A

The carbocation formed is known as a secondary carbocation
(The other product, 1-bromopropane, is formed through a primary carbocation)
The secondary carbocation is more readily formed and is more stable

197
Q

2 products of the electrophillic addition of hydrogen bromide to Propene

A

2-bromopropane
1-bromopropane

198
Q

Secondary carbocation

A

The positive charge is on a carbon atom to which 2 carbons are attached to

199
Q

Which carbocation forms 1-bromopropane?

A

A primary carbocation
CH3CH2CH2+

200
Q

What’s different betweeen a secondary carbocation and a primary carbocation?

A

More readily formed
More stable

201
Q

Equation for the primary carbocation formed in the production of 1-bromopropane via the electrophillic addition of hydrogen bromide to Propene

A

CH3CH2CH2+

202
Q

Equation for the secondary carbocation formed in the production of 2-bromopropane via the electrophillic addition of hydrogen bromide to Propene

A

CH3CH+CH3

203
Q

Secondary symbol

A

2°

204
Q

Primary symbol

A

1°

205
Q

Who discovered the rule which correctly predicts the major product formed in the addition of hydrogen bromide to an asymmetrical alkene?

A

Vladimir Markovnikoff

206
Q

What did Vladimir Markovnikoff discover?

A

The rule which correctly predicts the major product formed in the addition of hydrogen bromide to an asymmetrical alkene

207
Q

State what Vladimir Markovnikoff discovered

A

When hydrogen bromide adds to a double bond of an asymmetrical alkene, the hydrogen joins to the carbon that has the most hydrogen atoms bonded to it

208
Q

How do polymers occur?

A

Naturally and synthetically

209
Q

Name some natural polymers

A

Proteins such as the skin, hair, starch and cellulose

210
Q

What are addition polymers formed from?

A

Alkenes

211
Q

What do the alkenes that undergo addition polymerisation form?

A

Addition polymers

212
Q

Which process must alkenes undergo to form addition polymers?

A

Addition polymerisation

213
Q

What happens during addition polymerisation?

A

Alkene molecule adds on to the end of another alkene molecule to form a chain of thousands of alkene molecules

214
Q

Starting molecule of a polymer

A

Monomer

215
Q

Describe monomers

A

Unsaturated

216
Q

End product of polymerisation

A

Polymer

217
Q

Describe polymers

A

Saturated

218
Q

What always has and what never has a double bond?

A

Always = monomers
Never = polymers

219
Q

What are addition polymers formed from?

A

1 monomer as a repeating unit

220
Q

What is required to start a polymerisation reaction?

A

Catalyst
High temperature
High pressure

221
Q

Substituted alkenes

A

Not just hydrogen attached to the carbon

222
Q

What are 4 important polymers to remember?

A

Polypropene
PTFE (Teflon)
PVC (polychloroethene)
Polystyrene

223
Q

What’s the polymer PTFE also known as?

A

Teflon

224
Q

What’s the polymer PVC also known as?

A

Polychloroethene

225
Q

What’s polychloroethene also known as?

A

PVC

226
Q

What’s the polymer Teflon also known as?

A

PTFE

227
Q

What are all of the important polymers for us to remember examples of?

A

Thermoplastics

228
Q

Polypropene polymer…
Monomer
Monomer equation
Repeat unit
Uses

A

Propen
CH3CH=CH2
(Notes)
Pipes, ropes

229
Q

PTFE/Teflon polymer…

Monomer
Monomer equation
Repeat unit
Uses

A

Tetrafluroethene
CF2=CF2
(Notes)
Non stick pans

230
Q

PVC/polychloroethene…

Monomer
Monomer equation
Repeat unit
Uses

A

Chloroethene
CHCl=CH2
(Notes)
Floor tiles, tubing, film windows, rain coats, vinyl records

231
Q

Polystyrene..

Monomer
Monomer equation
Repeat unit
Uses

A

Phylethene (styrene)
C6H5CH=CH2
(Notes)
Packaging, mouldings

232
Q

What’s the relationship between the repeating units and monomers of a polymer?

A

Equal number of them

233
Q

What the styrene monomer also known as?

A

Phenylethene

234
Q

Phenylethene monomer’s other name

A

Styrene

235
Q

How to we identify a repeating unit in a polymer?

A

Take any 2 Ar on atoms in the main chain and draw any atoms above and below
Add square brackets and a value for “n”

236
Q

How do we identify the monomer of a polymer?

A

Take any 2 carbon atoms, write the atoms above and below it
Add a double bond

237
Q

Conditions for the polymerisation of ethene

A

2000atm
250 degrees
Trace of oxygen (initiator)

238
Q

What does oxygen act as in the polymerisation of ethene?

A

Initiator

239
Q

How does oxygen initiate the polymerisation of ethene?

A

Homolysis of the initiator results in the formation of radicals which react with ethene

240
Q

What happens to oxygen, the initiator of the polymerisation of Ethene?

A

Homolysis

241
Q

What does the homolysis of the initiator oxygen, result in for the polymerisation of ethene?

A

The formation of radicals which react with ethene

242
Q

What does the polymerisation of ethene involve?

A

Free radicals

243
Q

What does the fact that the polymerisation of ethene involves radicals mean for it?

A

The reaction is very rapid

244
Q

What happens during the course of the polymerisation of ethene?

A

Ethene molecules add to the end of the chain until a termination reaction occurs

245
Q

What dorms from the polymerisation of ethene?

A

Polymer chains of varying length
(Usually contain thousands of monomer units)

246
Q

What stops the polymerisation of ethene?

A

A termination reaction

247
Q

What are the 3 ways of classifying polymers?

A

Uses
Structure
Type of polymer

248
Q

3 uses of polymers

A

Plastics, fibres, elastomers

249
Q

2 structures of polymers

A

Thermoplastics
Thermosets

250
Q

Thermoplastics

A

Soften when heated and adopt a new structure when cooled

251
Q

Thermosets

A

Bonds between the polymer chains are more resistant to heat than thermoplastics

252
Q

2 examples of thermoset polymers

A

Bakelite
Melamin

253
Q

What’s the Bakelite thermoset in?

A

Light sockets

254
Q

2 types of polymer

A

Addition
Condensation

255
Q

What do the properties of a polymer depend on?

A

Structure
Method used to prepare
Whether other substances were added
Manufacturing technique

256
Q

What are the environmental problems of synthetic polymers?

A

Do not biodegrade
End up in landfill
End up in soil for centuries

257
Q

Why do a lot of polymers end up in landfill?

A

Poor tensile strength
Poor resistance to heat

258
Q

Why are polymers so widespread?

A

They’re cheap

259
Q

Which atoms does the sigma bond occur between?

A

C-C
and
C-H

260
Q

Which atoms does the pi bond occur between?

A

C-C

261
Q

Which type of bond do both alkanes and alkenes contain?

A

Sigma bonds

262
Q

If an alkene reacts with x in a 1:3 ratio, what does this mean?

A

There are 3 double bonds

263
Q

Which react most readily - alkanes or alkenes?

A

Alkenes

264
Q

Why do alkenes react more readily than alkanes?

A

Pi bond is weaker than the sigma bond and so is easily broken
The pi bond has a high electron density

265
Q

Bonds in alkanes and bonds in alkenes

A

Alkanes = only sigma bonds
Alkenes = pi bonds and sigma bonds

266
Q

Alkanes method of reacting with halogens

A

Radical substitution

267
Q

Alkenes method of reacting with halogens

A

Electrophillic addition

268
Q

What can the pi bond in an alkene be described to have?

A

High electron density

269
Q

What do we do if asked to draw 2 repeat units of a polymer?

A

Show what is repeated twice (see notes, it makes more sense)

270
Q

What feature of a molecule gives rise to E-Z isomerism?

A

Carbon to carbon double bond

271
Q

Where do we ALWAYS shows the movement of the line pair of electrons from when drawing reaction mechanisms?

A

From the lone pair of electrons

272
Q

What should you always show as the bare minimum when showing the termination stages of the free radical substitution reaction of alkanes?

A

The reaction between the free radicals that forms the originally desired product

273
Q

What must we not forget when drawing a product of addition polymerisation?

A

Square brackets

274
Q

What’s the difference between the products of homolytic bond fission and heterolytic bond fission?

A

Homolytic - forms free radicals
Heterolytic - forms an electrophile and a nucleophile

A level Chemistry (39 decks)

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