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LC Chemistry > Hydrocarbons and Fuels > Flashcards

Hydrocarbons and Fuels Flashcards

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1
Q

saturated hydrocarbons

A

compounds where there are only C-C single bonds between the C atoms in the molecule

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2
Q

unsaturated hydrocarbons

A

compounds where there is one or more double or triple C-C bond in the molecule

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3
Q

homologous series

A

a series of compounds with similar chemical properties
have graduations in physical properties
same general formula for its members
each member has a similar method of preparation
each member differs from the previous member by a CH2 unit

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4
Q

what is a homologous series another name for

A

a family of organic compounds

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5
Q

what is the system used to name compounds

A

the IUPAC system

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6
Q

what is the prefix for 1 C

A

meth

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7
Q

what is the prefix for 2 C

A

eth

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8
Q

what is the prefix for 3 C

A

prop

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9
Q

what is the prefix for 4 C

A

but

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10
Q

what is the prefix for 5 C

A

pent

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11
Q

what is the prefix for 6 C

A

hex

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12
Q

what is the prefix for 7 C

A

hept

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13
Q

what is the prefix for 8 C

A

oct

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14
Q

what is the prefix for 9 C

A

non

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15
Q

what is the prefix for 10 C

A

dec

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16
Q

are alkanes unsaturated or saturated

A

saturated

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17
Q

what do alkanes end in

A

ane

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18
Q

what is the general formula of an alkane

A

CnH2n+2

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19
Q

what is a chloroalkane

A

an alkane where 1 or more H atoms have been replaced by chlorine atoms

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20
Q

are chloroalkanes soluable in water

A

no - non polar

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21
Q

do chloro alkanes have a higher or lower boiling point than alkanes

A

higher
atoms with a larger electron density have stronger van der waals
more energy is needed to over come this force of attraction

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22
Q

structural isomers

A

compounds with the same molecular formula but different structural formula

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23
Q

what are the 2 side groups

A

methyl and ethyl

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24
Q

when are you able to have an ethyl side group?

A

when there are 7 or more C in the central chain
has to be more than 3 carbons from the end

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25
Q

what is a methyl side group

A

CH3

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26
Q

what state are chloroalkanes at room temp

A

liquid

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27
Q

what is an ethyl side group

A

C2H5

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28
Q

where can you put a side group?

A

methyl- cant be on either end
ethyl has to be atleast 3 carbons away from either end

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29
Q

how do you name a compound with a side group

A

state what number carbon the side group is on. (do this for every side group on the compound
state side group. side groups are listed alphabetically
if there is more than one side group but di or tri
and then name the carbon chain and whether it is an alkane, alkene or alkyne

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30
Q

do saturated hydrocarbons react with H2?

A

they do not partake in addition reactions with h2

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31
Q

how do you number the carbons

A

start numbering from the side where the side group is present with the lowest number

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32
Q

does boiling point increase or decrease with chain length

A

increases

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33
Q

why does boiling point increase with longer chain length

A

longer chain molecules have a larger electron density
this gives rise to stronger van der waals between hydrocarbon molecules as temporary dipoles form more easily
more energy is needed to over come these interactions
thus bp is higher

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34
Q

are alkenes saturated or unsaturated

A

unsaturated due to the double bond

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35
Q

what do alkenes end in

A

ene

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36
Q

general formula of alkenes

A

CnH2n

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37
Q

how to name an alkene

A

you must reference where the double bond is.
number your carbons, whichever side the double bond is closer to one is the position of the double bond. name it inbetween the but and ene so it would be but-1-ene

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38
Q

what shape are carbons in alkanes

A

tetrahedral

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39
Q

what shape are carbons in alkenes

A

trrigonal planar

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40
Q

what shape are carbons in alkynes

A

linear

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41
Q

what type of reaction is involved in the preparation of ethene

A

elimination (dehydration)

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42
Q

uses of ethene

A

ripening of fruit

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43
Q

what is ethene

A

a colourless gas that smells sweet

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44
Q

what is the test for unsaturation

A

add bromine water and shake
if the bromine water changed from red to colourless unsaturation is present

or
add acidified potassium permanganate
unsaturation is present if there is a colour change from purple to colourless

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45
Q

what type of reaction are the tests for unsaturation

A

adititon reactions

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46
Q

write the balanced equation for the bromine test for unsaturation

A

ethene + bromine —->1,2-dibromoethane

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47
Q

what does ethene burn as

A

a luminous yellow flame

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48
Q

what are alkynes

A

compound where there is a c-c triple bond

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49
Q

what doe an alkyne end in

A

yne

50
Q

general formula of an alkyne

A

CnH2n-2

51
Q

what is the only alkyne you need to know

A

ethyne

52
Q

what is ethyne used in

A

welding tourches

53
Q

what type of reaction is the preparation of ethyne

A

substitution reaction

54
Q

what is ethyne

A

a sweet smelling gas that is insoluable in water

55
Q

what does ethyne burn as

A

a smoky yellow flame

56
Q

aliphatic compound

A

an organic compound that consists of open chains of carbon atoms and closed chain compounds that resemble them in chemical properties

57
Q

aromatic compounds

A

compounds that contain a benzene ring or structure in their molecules

58
Q

is benzene polar or non polar

A

non polar

59
Q

properties of benzene

A

liquid at room temp
highly toxic
not soluable in water

60
Q

why is benzene unreactive?

A

the 3 pi e- thst form the double bonds are delocalised over all 6 C atoms providing extra stability

61
Q

why doesnt benzene cause bromine water to change colour even though it is unsaturated?

A

it is not reactive enough due to delocalisation of e-

62
Q

what is the bond length in benzene

A

all c-c bond lengths are the same due to delocalisation of e-
the bond lengths are somewhere between a double a single bond

63
Q

what dimension is benzen

A

planar 2D

64
Q

what are the bond angles in benzene

A

120 between c atoms

65
Q

how many sigma electrons are there in benzene

A

3 on each c atom

66
Q

how many pi e- are there in benzene

A

6

67
Q

what is delocalisation

A

electrons are not fixed on one atom

68
Q

octane number

A

measure of the ability of a fuel to resist knocking/ auto-ignition

69
Q

auto ignition/ knocking

A

when the petrol air mixture ignites prematurely in a combustion engine

70
Q

is it better to have a high or low octane number

A

high

71
Q

which fuel has an octane number of 100

A

2,2,4- trimethyl-pentane

72
Q

which fuel has an octane number of 0

A

heptane

73
Q

what is 2,2,4 trimethyl-pentane’s octane number

A

100

74
Q

what is heptanes octane number

A

0

75
Q

what does it mean if a fuel has an octane number of 90?

A

it is as efficient as a fuel with a mixture of 90% 2,2,4 trimethyl-pentane and 10% heptane

76
Q

what are the factors that effect octane number

A

length of the hydrocarbon chain
degree of branching
cyclic or straight chain

77
Q

is it better to have a short or long chain length in relation to octane number

A

the shorter the chain the higher the octane number is

78
Q

is it better to have a high or low degree of branching in relation to octane number

A

high

79
Q

is it better to have a cyclic or straight chain in relation to octane number

A

cyclic chain = higher octane number

80
Q

why is lead no longer added to petrol?

A

it is toxic
it poisons the catalyst in the catalytic converter

81
Q

why was lead historically added to fuel

A

to increase octane number

82
Q

what are the ways of increasing octane number

A

isomerisation
catalytic cracking
dehydrocyclisation
adding oxygenates to fuel

83
Q

what is isomerisation

A

adding branches to straight alkane chains

84
Q

what alkanes are commonly involved in isomerisation in an oil refinery

A

heptane and pentane

85
Q

how to identify isomerisation from a balanced equation

A

the starting material has the same molecular formula as the product
the chain is shorter and has a higher degree of branching in the product

86
Q

catalytic cracking

A

breaking up of long chain hydrocarbons into shorter, more in demand hydrocarbons using heat and a catalyst

87
Q

how to identify catalytic cracking

A

starting with one long molecule and ending up with 2 shorter ones
one of the products is unsaturated (has a double bond)

88
Q

benefits of catalytic cracking

A

makes shorter chain more in demand hydrocarbons available
alkenes produced are used as feedstock for petrochemical industry

89
Q

what is dehydrocyclisation

A

use of catalysts to form ring/cyclic compounds

90
Q

what is produced from dehydrocyclisation

A

hydrogen

91
Q

how to identify dehydrocyclisation

A

a straight chain molecule forms a cyclic molecule and hydrogen is produced

92
Q

what is an oxygenate

A

a compound that contains oxygen

93
Q

what are 3 examples of oxygenates added to fuel to increase octane number

A

methanol, ethanol, MTBE

94
Q

what does MTBE stand for

A

methyl-tertiary-butyl-ether

95
Q

what are the benefits of adding oxygenates to fuel

A

increases octane number
makes fuel burn more cleanly

96
Q

will a compound with a high or low octane no be more likely to autoignite

A

low

97
Q

give some uses of hydrogen

A

fuel
ammonia production
manufacturing of margarine

98
Q

why is H a good fuel?

A

it burns cleanly- no greenhouse gases are released during combustion as water is the only product

it has a high kilogram calorific value
it has a high octane number

99
Q

what are the 2 methods of producing H for industry

A

steam reformation of natural gas
electrolysis of water

100
Q

what is steam reformation of natural gas

A

methane is reacted with steam over a suitable catalyst

101
Q

what is the balanced equation for steam reformation of natural gas

A

CH4 + H2O —-> 3H2 + CO

102
Q

what is electrolysis of water?

A

passing electricity through water using platinum electrodes and water is split into hydrogen and oxygen gas

103
Q

write a balanced equation for electrolysis of water

A

H2O —> H2 + 1/2 O2

104
Q

why does elemental H not occur in nature on earth as a fuel source

A

its explosive

105
Q

what is crude oil

A

a fossil fuel composed of a mixture of hydrocarbons and is one of the most useful materials on earth

106
Q

what is crude oil used for

A

it is a feedstock for the plastics industry
pharmacuticals

107
Q

what is fractional distillation

A

it separates crude oil into a number of different more useful fractions according to their different boiling points (chain length)

108
Q

which hydrocarbons are at the top of the column

A

C1- 4
(smaller chain hydrocarbons)

109
Q

why are mercaptans added to fuels?

A

to give them a smell so that gas leaks can be detected

110
Q

what are mercaptans

A

sulphur compounds added to fuel to give them a smell so that gas leaks can be detected

111
Q

describe how fractional distillation separates the different fractions in crude oil

A

->different fractions separate according to their different boiling points

->crude oil is pumped in at the bottom. a furnace is used to heat the crude oil and most fractions are vaporised and enter the tower

-> there is a temperature gradient in the tower - hotter at the bottom and colder at the top. the vaporised fractions travel up through the tower the substance with the highest boiling point emerge at the bottom of the tower (longest chain)

->bubble caps have small holes to slow down the rate the vapor rises. fractions condense at their boiling point and are collected in the trays and removed through outlets

112
Q

draw a diagram of fractional distillation

A
113
Q

what is refinery gas used for

A

domestic heating/cooking

114
Q

what is petrol used for

A

fuel for cars

115
Q

what is naphtha used for

A

feedstock for petrochemicals

116
Q

what is kerosine used for

A

fuel for aircraft

117
Q

what is diesel oil used for

A

fuels for buses trucks or trains

118
Q

use of lubricating oil

A

waxes and polishes

119
Q

use of fuel oil

A

fuel for ships

120
Q

use of bitumen

A

tar for roads and roofing

121
Q

hydrocarbon

A

a compound that contains only carbon and hydrogen atoms

122
Q

alkenes

A

a hydrocarbon with atleast 1 double c-c bond

LC Chemistry (22 decks)

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