6.2 Flashcards by bethany loughead

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

fractional distillation
cracking
reforming

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whats the order of the fractions of crude oil

gas
petrol
naptha
kerosene
disel
fuel oil
bitchumen

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what is fractional distillation

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

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what is cracking

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

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define reforming

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

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why do some hydrocarbons need reformed

straight chain hydrocarbons burn less efficiently then branched

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how is reforming done

heating with a catalyst e.g. platinum

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what is complete combustion & what are the products

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

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what is incomplete combustion & when can it occur

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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what can be formed in incomplete combustion

carbon monoxide
solid carbon

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how is carbon monoxide deadly

binds to hemoglobin
prevents transport of oxygen
colourless & odorless gas

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

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

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how does nitrogen form acid rain during combustion

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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what metals are used in catalytic converters

platinum
rhodium
palladium

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

to increase surface area and reduce cost

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

sulfur compounds
they must be removed from the fuel

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why do we need alternative fuels

pollution
depletion of natural resources
global warming & climate change

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define biofuel

fuels obtained from living matter that has died recently

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define renewable

energy sources use sources that can be continuously replaced

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define non-renewable

energy sources are not being replenished except over geological timescales

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what is biodiesel

fuel made from vegetable oils obtained from plants

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what is bioalcohol

fuels made from plant matter often using enzymes or bacteria

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compare biofuels & natural gases

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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what is a substitution reaction

an atom or group is replaced by another atom or group

what is homolytic fission

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

what is a radical

a species that contains an unpaired electron

what is the mechanism for the chlorination of methane

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

what is the final step in the chlorination of methane

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

what is initiation

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

what is propagation

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

what is termination

formation of a molecule from two radicals

what are sigma bonds

covalent bonds formed when electron orbitals overlap axially

what are pi bonds

covalent bonds formed when electron orbitals overlap sideways

which are stronger sigma or pi bonds and why

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

what is a test for a C=C bond

add bromine goes from orange/brown to colourless

what is an addition reaction

a reaction in which two molecules combine to form one

define hydrogenation

addition of hydrogen

what is hydration

addition of water

what are usually the conditions for hydration reactions

heated with catalyst of phosphoric acid

what is a diol

compound containing two OH groups

what does [O] mean in an equation

represents the oxygen supplied by oxidizing agent

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

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

what do curly arrows show

movement of electron pairs

define electrophile

species that is attracted to a region of high electron density

what is electrophilic addition

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

define heterolytic fission

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

what is a carbocation

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

describe step 2 of the mechanism of addition reactions

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

what is an unsymmetrical alkene

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

what is an unsymmetrical attacking molecule

one in which the atoms are different

what makes a carbocation secondary

it is attached to two other carbons

why are secondary carbocations more stable than primary carbocations

the positive charge can be spread over more atoms

what is an electron releasing group

one that pushes electrons towards the atom it is joined to

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

more stable

is the most stable product formed the major or minor product

major

what are the general conditions for addition polymerization

high temperature high pressure

define monomer

small molecules that combine together to form a polymer

why are polymers (plastics) so popular

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

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

-recycling -incineration -chemical feedstock