6.2 Flashcards
what are the 3 main processes of converting crude oil to fuels
fractional distillation
cracking
reforming
whats the order of the fractions of crude oil
gas
petrol
naptha
kerosene
disel
fuel oil
bitchumen
what is fractional distillation
the process used to separate a liquid mixture into fractions by boiling and condensing
what is cracking
the breakdown of molecules into shorter ones by heating with a catalyst
define reforming
the conversion of straight chain hydrocarbons into branched chain and cyclic hydrocarbons
why do some hydrocarbons need reformed
straight chain hydrocarbons burn less efficiently then branched
how is reforming done
heating with a catalyst e.g. platinum
what is complete combustion & what are the products
all of the atoms in the fuel are fully oxidized produces water & CO2
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
what can be formed in incomplete combustion
carbon monoxide
solid carbon
how is carbon monoxide deadly
binds to hemoglobin
prevents transport of oxygen
colourless & odorless gas
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
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
what metals are used in catalytic converters
platinum
rhodium
palladium
why are the metals spread thinly over a honeycomb mesh in catalytic converters
to increase surface area and reduce cost
which harmful molecule produced in combustion is not stopped by the catalytic converter
sulfur compounds
they must be removed from the fuel
why do we need alternative fuels
pollution
depletion of natural resources
global warming & climate change
define biofuel
fuels obtained from living matter that has died recently
define renewable
energy sources use sources that can be continuously replaced
define non-renewable
energy sources are not being replenished except over geological timescales
what is biodiesel
fuel made from vegetable oils obtained from plants
what is bioalcohol
fuels made from plant matter often using enzymes or bacteria
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
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
