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
what is different about the combustion of alkenes as opposed to alkanes
alkenes undergo incomplete comnustion
what does combustion of alkenes create
water
carbon dioxide
unburnt carbon particles
what do you see with the incomplete combustion of alkenes
they burn in air with a smoky flame
what is hydrogenation
when alkenes react with hydrogen
(with a catalyst)
to produce an alkane
what conditions are needed for hydrogenation
( alkene reacting with hydrogen to form an alkene)
150 degrees
nickel catalyst
how is an alkane created when an alkene reacts with hydrogen
by the addition of atoms across c=c double bond
which splits to form a c-c single bond
what is the hydration of an alkene
think about water, getting drunk…
when an alkene is
reacted with steam
to produce an alcohol
(needs high pressure and a catalyst)
what conditions are needed for the hydration of alkenes
300 degrees
70 atm
phosphoric acid catalyst
what is unique about the hydration of alkenes reaction
it is reversible
to increase yield of ethanol unreacted ethene and steam can be passed back through the catylyst
what halogens do alkenes react with
chlorine
bromine
iodine
what are the conditions for the reaction of alkenes and halogens
no special conditions
word equation for reaction of alkene and halogen
alkene + halogen =
di halogen alkane
where the halogen is one of the following : (iodo, bromo, chloro)
why does the reaction of halogens and alkenes form a dihalogenalkane
the halogen atoms add across the double bond
double c=c bond breaks
so no longer an alkene
halogens are diatomic hence (di)
important thing to remember about halogens
All of the halogens exist as diatomic molecules
a pair of atoms chemically bonded
first 4 alkenes
ethene
propene
buene
pentene
functional group of alcohols
O-H
what are alcohols used as
fuels
solvents eg
( perfume, mouthwash)
what can ethanol be used in
alcoholic drinks
structural formula for methanol
( a simplified version that scientists use)
CH3OH
structural formula for ethanol
CH3CH2OH
structural formula for propanol
CH3CH2CH2OH
structural formula for butanol
CH3CH2CH2CH2OH
2 ways to make ethanol
hydration of ethene
fermentation of sugar
advantage of hydration of ethene to make ethanol
high yeild
disadvantage of hydration of ethene to make ethanol
needs a lot of energy
ethene comes from finite crude oil
describe process of fermentation of sugar to make ethanol
mix sugar solution with yeast
yeast converts sugar solution to a solution of ethanol (aq)
what conditions are needed for the fermentation of sugar to produce ethanol
30 degrees
anaerobic conditions
(without o2)
adavantages of using fermentation of sugar to produce ethanol
low temp -not much energy
sugar from plants - renewable
disadvantages of using fermentation of sugar to produce ethanol
ethanol produced is dissolved in water (aq)
must then be distilled to get pure ethanol
this distillation requires energy
are alcohols soluble in water
yes
what type of solutions do alcohols form
alcohols form neutral solutions
what happens to solubility of alcohols as the carbon chain increases
as the number of carbon atoms increases, the solubility decreases.
word equation for reaction between alcohol and sodium
alcohol + sodium = alkoxide + hydrogen
complete the following reaction for ethanol and sodium
ethanol + sodium =
sodium ethoxide + hydrogen
what happens when an alcohol reacts with sodium
hydrogen in released
alkoxide is formed
what happens when alkoxides are added to water
if alkoxides are added to water they form strongly alkaline solutions
what happens when alcohols react with an oxidising agent
they produce a carboxylic acid and water
word equation for ethanol and oxidising agent
ethanol= ethanoic acid and water
word equation for combustion of alcohols
alcohol + oxygen = carbon dioxide + water
what happens when alcohol undergoes combustion
energy is released
balance the following combustion equation of ethanol
C(2)H(5)OH + O(2) =
CO(2) + H(2)O
first balance carbons
2 on reactants
1 on products
- so put large 2 infront of CO(2)
now balance hydrogen atoms
6 on reactants
2 on products
- so put large 3 infront of H(2)O
now there are 6 hydrogens on products
lastly balance Oxygen
3 on reactants- C(2)H(5)OH & O(2)
7 on products - 2CO(2) & 3H(2)O
- so as you need 4 more oxygens in reactants put large 2 infront of O(2)
so….
C(2)H(5)OH + 2O(2) =
2CO(2) + 3H(2)O
balance C4H9OH + O2 = CO2 + H2O
C4H9OH + 6O2 = 4CO2 + 5H2O
what are the 4 reactions of alcohols that you need to learn
sodium
burn in air
added to water
oxidising agent
functional group of carboxylic acid
OH-C=O
structural / displayed formula for methanoic acid
HCOOH
structural / displayed formula for ethanoic acid
CH3COOH
structural / displayed formula for propanoic acid
CH3CH2COOH
structural / displayed formula for butanoic acid
CH3CH2CH2COOH
what happens when carboxylic acids are added in water
they are partially ionised to form weakly acidic solutions
they lose a hydrogen
in water what are carboxylic acids
weak acids
what is formed when ethanoic acid is dissolved in water
a negative eth(anoate) ion
a positive hydrogen ion
why are carboxylic acids weak acids
they only partially ionise in aqueous solution
what does it mean when you say carboxylic acids only partially ionise
the carboxylic acid molecules dont all release their hydrogen ions
compare ph of carboxylic acids (weak) and strong acids
carboxylic acids have a higher ph than strong acids
eg hydrochloric acid
word equation for carboxylic acid + metal carbonate
carboxylic acid + metal carbonate = salt + water +carbon dioxide
complete word equation for propanoic acid +potassium carbonate
propanoic acid +potassium carbonate =
potassium propanoate + water + carbon dioxide
what is formed from reacting carboxylic acid and alcohol
an ester + water
what are esters used in/ why
foods/ perfumes
have a nice smell
name an ester and how its made
ethanoic acid+ ethanol= ethyl ethanoate
what catalyst is needed to produce ethyl ethanoate
sulfuric acid catalyst
is the reaction between a carboxylic acid and alcohol reversible
yes
how are carboxylic acids made
by reacting an alcohol and an oxidising agent
the reaction of a carboxylic acid dissolved in water is reversible. what does this mean
the ethanoate ion and H+ ion can recombine to a carboxylic acid.
what is a monomer
the identical molecules that are added to create a polymer
what is an addition polymer
a polymer made up of alkene monomers
what is a repeating unit
the short hand way of showing the structure of a polymer is called
how are polymers made
by adding together thousands of small identical molecules
what are the two types of polymers
addition
condensation
do additon polymers have the double c=c bond like its seperate monomers
no
how are polymers named
poly,
followed by the name of the
monomer
the short hand way of showing the structure of a polymer is called
the repeating unit
how do you work out the repeating unit of a polymer
take any two carbon atoms that are next to eachother
draw these with the hydrogens attatched
put in brackets with a small n on the right
what should you remember about the atoms in a polymer and its monomer
all the atoms in the monomer end up in the polymer
what is the polymer for chloroethene called
poly(chloroethene)
how are esters formed
carboxylic acid + alcohol
(sulfuric acid catalyst)
= ester
what is meant by a condensation polymer
