fractional distillation and cracking Flashcards
what is crude oil
fossil fuel made from remains of ancient biomass
what are the first 4 alkenes
methane
ethane
propane
butane
formula to work out alkene
Cn H2n+2
hydrocarbon
compound only with hydrogen and carbon
what is the use of petrol
fuel for cars
what is the use of naphtha
used to manufacture chemicals
what is the use of bitumen
used for laying roads
what is the use of kerosene
fuel for aircrafts
what is the use for diesel
fuel for cars, vans and lorries
what is fractional distillation
separate components with different condensing temperatures in a mixture
where does fractional distillation take place
fractionating column
what is cracking
breaking down large molecules in to smaller more useful ones
where does cracking take place
oil refinery in steel vessels
how does cracking work
heavy fractional of distilled crude oil is heated to vaporise hydrocarbons
what happens to the vapour in cracking
passed over a hit catalyst
mixed with steam and heated ti a very high temp
what is cracking an example of
thermal decomposition
why is cracking so important
to meet demands for fuels
how can large hydrocarbon molecules be cracked in an oil refinery
hydrocarbon vapours passed over a hot catalyst
unsaturated hydrocarbon
hydrocarbon containing at least 1 C=C double bond
type of bonding in hydrocarbons
covalent
what properties would you expect from a hydrocarbon
low boiling point due to covalent bond (molecules)
How many bonds does each hydrogen atom need to make?
1
How many bonds does each carbon atom need to make?
4
why are hydrocarbons good fuels?
with OXYGEN exothermically producing CO2 and steam
why are hydrocarbons better fuels that wood /coal?
don’t make ash
so there is no need to clean out the combustion chamber
what problems are associated with using hydrocarbons as fuel?
CO2 is a greenhouse gas
climate change
how many joules of energy does 1 mole go petrol release
(assuming complete combustion)
6770kJ
define a FUEL
substance that releases energy when burnt
properties of alkanes
saturated
no double bonds
properties of short chain hydrocarbons
low BP and MP
very flammable
low viscosity
word equation for complete combustion
Fuel +oxygen - >carbon dioxide + water
when are alkenes formed
when we crack large alkanes
uses of alkenes
used to make polymers and plastic
do we use alkenes for fuel
no
test for alkenes
bromine water
positive test becomes colourless
negative test stays orange
how to draw alkenes
1 double bond between the carbons
