C14 - Organic chemistry Flashcards
What is a hydrocarbon
an organic compound made up of purely hydrogen and carbon
what are the properties of short and long chained hydrocarbons
short chained: lower melting point, lower viscosity, more flammable
Long chained: Higher melting point, higher viscosity, less flammable
Fractional distillation separates
crude oil into simpler, more useful mixtures.
Naphtha (in between gasoline and kerosene) used for
making chemicals.
Lubricating oil (in between fuel oil and bitumen) used for
lubricants, waxes and polishes.
Petrol use
fuel for cars
refinery gas use
domestic heating and cooking
kerosene use
fuel for aircrafts
Diesel oil use
cars and trains
fuel oil use
fuel for ships and power stations
Bitumen use
surfacing roads and roofs
How does fractional distillation separate crude oils
it is heated in a furnace and passed into the bottom of a fractionating column. It gives off mixtures of vapors that rise up the column and different fractions condense at different heights in which the liquids are collected at trays.
The homologous series is a series of
compounds with the same general formula and similar chemical properties
The physical properties that can change in a homologous series
As chains get longer boiling points increase
Each new chain adds on another CH2
why does the boiling point of hydrocarbons increase as chains get longer
because there are more and more intermolecular forces between the molecules (although weak still add up)
what is the alkane molecular structure
carbon atoms are bonded to 4 other atoms (hydrogen or carbon)
alkanes are called saturated hydrocarbons because
they only contain single bonds with other atoms
Uses of alkanes
They are unreactive
they can burn well making them a good source for fuel
General formula for alkane
CnH(2n+2) (For example: if hydrocarbon has 7 carbons than the formula is C7H16
Alkanes will react with chlorine in the presence of a
UV light which activates the chlorine to react
The reaction between alkane and chlorine is called
substitution reaction as one hydrogen atom in the hydrocarbon is replaced with one chlorine atom
the products of a alkane chlorine reaction are
chloroalkane + hydrogen chloride
What are the 4 smallest hydrocarbons in ascending order
methane, ethane, propane, butane
In an abundant supply of air alkanes burn to form
CO2 + water and is called complete combustion of alkanes in which a blue flame will be present
word and symbol equation for the complete combustion of alkanes
methane + oxygen ==> carbon dioxide + water
CH4(g) + 2O2(g) ==> CO2(g) + 2H2O(l)
When oxygen supply is limited incomplete combustion occurs in which the presence of a
yellow flame to show that
word and symbol equation for the incomplete combustion of alkanes
methane + oxygen ==> carbon + water
CH4(g) + O2(g) ==> C(g) + 2H2O(l)
Incomplete combustion of hydrocarbon can be dangerous because it can produce
carbon monoxide which is poisonous
Heavy Fractions of Crude Oil do not make good fuels as they
have low volatility, do not ignite easily and have high boiling points
What is the process of cracking
breaking down long chains of hydrocarbons into smaller more useful molecules. It is an example of thermal decomposition
What are the products of cracking
an alkane and an alkene
What are the requirements to perform cracking
a higher temperature of around 600 - 700 C
a catalyst of silica or alumina
Alkenes are another
homologous series which have similar chemical and physical properties that change gradually from one member to the next
Alkenes are a functional group C=C meaning
they have a carbon-carbon double bond
Properties and uses of alkenes
More reactive than alkanes
General molecular formula of CnH2n
They are unsaturated hydrocarbons because they contain a double bond between 2 C atoms
Uses: Making polymers such as polythene
Burn in oxygen to form CO2 and H2O and CO if oxygen is limited
Alkenes are involved in
addition reactions
Hydrogen can be added to an alkene to make an
alkane
What are the requirements for an addition reaction between hydrogen and an alkene
A nickel catalyst
150 C temperature
H2
Word and symbol equation for addition reaction between hydrogen and an alkene
Ethene + hydrogen ==> ethane
C2H4 + H2 ==> C2H6
What test could you use to distinguish alkenes from alkanes or saturated hydrocarbon from unsaturated hydrocarbon
Add bromine water to hydrocarbon. Alkanes will not react with it in which there will be no color change but an alkene will react with bromine turning the color from orange to colorless.
What is the word equation for an addition reaction between bromine and alkene
Ethene + Bromine ==> 1,2 -dibromoethane
C2H4 + Br2 ==> C2H4Br2
Ethene can also react with steam to form
ethanol
What are the requirements for a reaction between steam and ethene
Phosphoric acid catalyst
300 C and 70 atm
H20
What is the word equation for an addition reaction between steam and ethene
ethene + steam ==> ethanol
C2H4 + H2O ==> C2H5OH
what is an isomer
isomer is same molecular formula but different structural formula
Alcohol properties and characteristics
functional group of alcohols is a hydroxyl group OH
They can be dehydrated to form alkenes
Ethanoic and butanoic acids react the same with metals meaning alcohols react similar ways
General formula (CnH2n + 1 OH)
Reactions of a ethanol with air forms
CO2 + H2O
ethanol + oxygen ==>
C2H5OH + 3O2 ==>
carbon dioxide + water
2CO2 + 3H2O
Uses of ethanol
Solvent - such as in disinfectants and perfumes
Fuel - such as cars
Alcoholic drinks - such as wine, beer and spirits
Ethanol can be made via
fermentation or addition of steam
In fermentation the reactant involved is
sugar and yeast. The sugar can be from barley in beer making and grapes from wine making.
Why is yeast used in fermentation
yeast contains an enzyme which acts as a catalyst breaking down the sugars in a much faster rate.
What are the requirements for fermentation
Temperature of around 25 - 30 C some say 37 C
What is the formula for sugar (glucose)
C6H12O6
What is the word and symbol equation for fermentation
sugar ==> ethanol + carbon dioxide
C6H12O6 ==> 2C2H5OH + 2CO2
What are the advantages and disadvantages of making ethanol from fermentation and from addition of steam
Fermentation: Plant sugars and renewable however creates waste products of CO2
Addition of steam: Fast and efficient however ethene is cracked from crude oil which is non-renewable and also requires a lot of energy.
What is a polymer
a long chained molecule formed from small units called monomers
Manufactured polymers are called
synthetic polymers
Common synthetic polymers include
plastics such as polythene and fabrics using clothing from polyester or polyamide.
What are the two types of synthetic polymers
addition and condensation polymers
polymers are held by
strong covalent bonds but weak intermolecular forces
Polymers melt easily because
there are weak intermolecular forces which can be broken down easily
Alkenes are monomers used
in addition polymerization because they can open up their double bonded carbon atoms and attach to other molecules forming chains of monomers
when ethene monomers undergo addition polymerization the product is
poly (ethene)
Condensation polymers are polymers made up of
2 different monomers reacting together
When the two monomers react in condensation polymers they expel a
small molecule which is water
Nylon is a
common synthetic condensation polymer
Nylon is made from a molecule with
carboxylic acid (COOH) and another molecule (NH2) and they react to form an amide link
Show ethene in a symbol equation for addition polymerization
nCH2 = CH2 ==> [CH2CH2]n
the n represents the repeating unit
the double bond “=” breaks and is replaced with “[]”
what is the difference between additional and condensation polymerization
additional polymerization results in the addition of many of the same monomers whilst condensation involves two different types of monomers which when reacted expel a molecule of water.
