Organic chemistry (spec) Flashcards
what is crude oil
a finite recourse found in rocks
crude oil is the remains of….
3 points
an ancient biomass
mainly plankton
that was buried in the mud
crude oil is a mixture of what
crude oil is a mixture of hydrocarbon molecules
what are hydrocarbons
molecules made up of hydrogen and carbon atoms ONLY
general formula of alkanes
Cn H2n+2
first 5 alkanes
methane
ethane
propane
butane
pentane
functional group of alkanes
there is none
why are alkanes said to be saturated
the carbon atoms are all fully bonded to hydrogen atoms
what are most of the hydrocarbons in crude oil called
alkanes
what can crude oil be used to produce
x4
plastic
petrol
pharmaceuticals
cosmetics
what does viscosity mean
the thickness of a fluid
what happens to visosity as the size of the hydrocarbon increases
the larger the hydrocarbon, the higher the viscosity
( flow slowly)
what does flammability tell us
how easily a hydrocarbon combusts
what happens to flammability as the size of hydrocarbon increseases
the larger the hydrocarbon, the lower the flammability
what can you say about flammability of long chain hydrocarbons
long chain hydrocarbons are very difficult to burn
what hydrocarbon is used in a bunsen burner. what does this show
methane is used in a bunsen burner
show short chain hydrocarbons are very flammable
what is boiling point
the temperature at which a liquid turns into a gas
at room temp, what is the state of the first four alkanes.
what does this show
gas
shows that short chain hydrocarbons have low boiling points
what are the boiling points of the first 4 alkanes (general)
lower than room temp
what happens to bp as the size of the hydrocarbon molecule increases
boiling point increases as size of hydrocarbon increases
what does the flammability, boiling point, and viscosity of hydrocarbons influence
boiling point, viscosity and flammability
influence how hydrocarbons are used as fuels.
when do hydrocarbon fuels release energy
hydrocarbon fuels release energy when COMBUSTED (burned)
during combustion of hydrocarbons,
what happens to the hydrogen and carbon atoms
the hydrogen and carbon atoms react with o2
THEY ARE OXIDISED
word equation for complete combustion of alkanes
hydrocarbon + oxygen = carbon dioxide + water
balance the following equation (complete combustion of methane)
CH4 + O2 = CO2 + H2O
first balance carbons
(already balanced)
then balance Hydrogen
4 in reactants
2 in products
- times products Hydrogen by 2
put large 2 infront of H2O
now balance Oxygen
2 in reactants
4 in products (because u added 2 infront of H2O)
put large 2 infront of reactants O2
=
CH4 + 2 O2 = CO2 + 2 H2O
fir the hydrocarbons in crude oil to be useful, what must we do first
separate them using fractional distillation
what happens through fractional distillation (brief)
2 points
crude oil is separated into fractions
fractions contain hydrocarbons with similar carbon number
process of fractional distillation
7 points
. crude oil is vaporised ( turned into gas by heating)
. the hydrocarbon gases enter the column
. column is hotter at bottom, cooler at top
. hydrocarbon gases rise up column
. as hydrocarbon gases rise up column, they cool down
. when hydrocarbons reach their boiling point in the column they condense (to liquid)
. hydrocarbon fractions then removed
where are the long chain hydrocarbons removed in the fractional column
explain why
at the bottom of the column
think of it like this :
long chain hydrocarbons have super high b.p
even at the bottom of the column, it’s not hot enough to keep these hydrocarbons as gases.
therefore they condense and can be collected
what happens to very short chain hydrocarbons in the fractional column
explain why
they are removed from the top of the column, still as gases
think of it like this:
.short chain hydrocarbons have really low boiling points
.all throughout the column, the temperature is hot enough to keep these as gases.
.and so they cannot condense and are taken out from the top still in gas form
name 5 products of fractional distillation that are used as fuels
ppk dh !
petrol,
diesel,
kerosene,
heavy fuel oil and
liquefied petroleum gases
what does feedstock mean
a chemical used to make other chemicals
the fractions can be processed to make feedstock
Feedstocks are used by the petrochemical industry to make things like:
solvents
lubricants
detergents
polymers
2 key features of alkanes
. their general formula CnH2n+2
. only single covalent bonds between atoms
why do long chain hydrocarbons NOT make good fuels
they are not very flammable
what is cracking used for.
Hydrocarbons broken down (cracked) to produce smaller,
more useful molecules
what is created from cracking a long chain alkane
smaller
alkanes and alkenes
2 ways to carry out cracking
catalytic cracking
steam cracking
summarise process of catalytic cracking
vaporise the hydrocarbons through high temp
then pass them over a hot catalyst ( to speed up reaction)
summarise process of steam cracking
mix the hydrocarbons with steam at a very high temperature
why are alkenes useful, what can they be used for
to produce polymers
as a starting material for other chemicals
functional group of alkenes
one c=c double bond
whats more reactive, alkene or alkane
alkene
how to test for alkene
3 steps
.add the molecule to orange .bromine water
shake
. urns colourless if alkene was added
balance the following equation
( cracking of a long chain hydrocarbon )
C25 + H52 = C20 + H42 + C…H….
C25 + H52 = C20 + H42 + C5H10
general formula of alkenes
CnH2n
what does the displayed formula show us
all the atoms and the ecovalent bonds eg
h h
l l
c=c
l l
h h
why are alkenes unsaturated
they have 2 less hydrogen atoms
than an alkene with the same carbon number
what does functional group mean
the part of a molecule that determines how it reacts
how do you know if molecules belong to the same homologous series
they will have the same functional group