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Chemistry > 6.2 > Flashcards

6.2 Flashcards

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1
Q

what are the 3 main processes of converting crude oil to fuels

A

fractional distillation
cracking
reforming

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2
Q

whats the order of the fractions of crude oil

A

gas
petrol
naptha
kerosene
disel
fuel oil
bitchumen

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3
Q

what is fractional distillation

A

the process used to separate a liquid mixture into fractions by boiling and condensing

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4
Q

what is cracking

A

the breakdown of molecules into shorter ones by heating with a catalyst

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5
Q

define reforming

A

the conversion of straight chain hydrocarbons into branched chain and cyclic hydrocarbons

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6
Q

why do some hydrocarbons need reformed

A

straight chain hydrocarbons burn less efficiently then branched

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7
Q

how is reforming done

A

heating with a catalyst e.g. platinum

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8
Q

what is complete combustion & what are the products

A

all of the atoms in the fuel are fully oxidized produces water & CO2

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9
Q

what is incomplete combustion & when can it occur

A

some of the atoms in the fuel are not fully oxidized
occurs when there’s insufficient oxygen present or when combustion is very rapid

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10
Q

what can be formed in incomplete combustion

A

carbon monoxide
solid carbon

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11
Q

how is carbon monoxide deadly

A

binds to hemoglobin
prevents transport of oxygen
colourless & odorless gas

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12
Q

how does the release of sulfur during combustion of alkanes contribute to acid rain

A

react in atmosphere to form sulfur trioxide
dissolve in water in the atmosphere
fall as acid rain damaging the environment

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13
Q

how does nitrogen form acid rain during combustion

A

nitrogen molecules in the air react with the oxygen molecules to produce nitrogen oxides which dissolve in the atmosphere to produce acid rain

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14
Q

what metals are used in catalytic converters

A

platinum
rhodium
palladium

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15
Q

why are the metals spread thinly over a honeycomb mesh in catalytic converters

A

to increase surface area and reduce cost

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16
Q

which harmful molecule produced in combustion is not stopped by the catalytic converter

A

sulfur compounds
they must be removed from the fuel

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17
Q

why do we need alternative fuels

A

pollution
depletion of natural resources
global warming & climate change

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18
Q

define biofuel

A

fuels obtained from living matter that has died recently

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19
Q

define renewable

A

energy sources use sources that can be continuously replaced

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20
Q

define non-renewable

A

energy sources are not being replenished except over geological timescales

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21
Q

what is biodiesel

A

fuel made from vegetable oils obtained from plants

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22
Q

what is bioalcohol

A

fuels made from plant matter often using enzymes or bacteria

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23
Q

compare biofuels & natural gases

A

biofuel:
land required to grow crops
low yield
transportation costs
almost carbon neutral
natural gas:
no land required
underground source
high yield
drilling, transport & processing costs
not carbon neutral

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24
Q

what is a substitution reaction

A

an atom or group is replaced by another atom or group

25
Q

what is homolytic fission

A

breaking of a covalent bond where each of the bonding electrons leaves with one species forming a radical

26
Q

what is a radical

A

a species that contains an unpaired electron

27
Q

what is the mechanism for the chlorination of methane

A

initiation
Cl2 -> Cl’ + Cl’
propagation
Cl’ + CH4 -> HCl + CH3’
CH3 + Cl2 -> CH3Cl + Cl’

28
Q

what is the final step in the chlorination of methane

A

termination
Cl’ + Cl’ -> Cl2
Cl’ + CH3’ -> CH3Cl
CH3’ + CH3’ -> C2H6

29
Q

what is initiation

A

first step in forming radicals as a result of bonds breaking caused by uv radiation

30
Q

what is propagation

A

two steps that when repeated start converting materials into the products of a reaction

31
Q

what is termination

A

formation of a molecule from two radicals

32
Q

what are sigma bonds

A

covalent bonds formed when electron orbitals overlap axially

33
Q

what are pi bonds

A

covalent bonds formed when electron orbitals overlap sideways

34
Q

which are stronger sigma or pi bonds and why

A

sigma bond is stronger as electrons are more tightly held between the two carbon atoms and involves end on end overlap so there is a larger area of overlap

35
Q

what is a test for a C=C bond

A

add bromine
goes from orange/brown to colourless

36
Q

what is an addition reaction

A

a reaction in which two molecules combine to form one

37
Q

define hydrogenation

A

addition of hydrogen

38
Q

what is hydration

A

addition of water

39
Q

what are usually the conditions for hydration reactions

A

heated with catalyst of phosphoric acid

40
Q

what is a diol

A

compound containing two OH groups

41
Q

what does [O] mean in an equation

A

represents the oxygen supplied by oxidizing agent

42
Q

how can alkanes and alkenes be distinguished using potassium manganate (VII)

A

alkanes - no reaction
alkenes - solution goes from purple to colourless

43
Q

what do curly arrows show

A

movement of electron pairs

44
Q

define electrophile

A

species that is attracted to a region of high electron density

45
Q

what is electrophilic addition

A

reaction where two molecules form one and the attacking molecule is an electrophile

46
Q

define heterolytic fission

A

breaking of a covalent bond so that both bonding electrons are taken by one atom

47
Q

what is a carbocation

A

positive ion in which the charge is shown on a carbon atom

48
Q

describe step 2 of the mechanism of addition reactions

A

two oppositely charged ions attract each other and react to form a new covalent bond

49
Q

what is an unsymmetrical alkene

A

atoms on eitherside of the C=C bond are not the same

50
Q

what is an unsymmetrical attacking molecule

A

one in which the atoms are different

51
Q

what makes a carbocation secondary

A

it is attached to two other carbons

52
Q

why are secondary carbocations more stable than primary carbocations

A

the positive charge can be spread over more atoms

53
Q

what is an electron releasing group

A

one that pushes electrons towards the atom it is joined to

54
Q

are carbocations more or less stable when there are more electron-releasing alkyl groups

A

more stable

55
Q

is the most stable product formed the major or minor product

A

major

56
Q

what are the general conditions for addition polymerization

A

high temperature
high pressure

57
Q

define monomer

A

small molecules that combine together to form a polymer

58
Q

why are polymers (plastics) so popular

A

-large scale production
-lots of variety
-light
-unreactive
-cheap

59
Q

what are the three main ways of disposing of polymers (plastics)

A

-recycling
-incineration
-chemical feedstock

Chemistry (46 decks)

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