Organic Chemistry Flashcards
what is crude oil
a finite resource found in rocks.
- mixture of hydrocarbons
what are hydrocarbons
molecules that contain hydrogen and carbon atoms only.
what is crude oil made of
Formed over millions of years from the remains of tiny sea creatures called plankton, which were buried in the mud
formula for alkanes
CnH2n+2
what are the first four alkanes
- methane
- ethane
- propane
- butane
what are some of crude oil uses
- fuels such as petrol, diesel, kerosene, heavy fuel oi
solvents
lubricants
detergents
liquified petroleum gas
what is a homologous series
a family of organic compounds which have the same functional group and similar chemical properties
properties of alkanes
- have the same general formula
- show a gradual variation in physical properties, such as their boiling points
- have similar chemical properties
what are saturated hydrocarbons
hydrocarbons which have single carbon to carbon bonds, like alkanes
what technique is used to separate crude oil
fractional distillation
why is fractional distillation used
because different hydrocarbons have different boiling points
how does the distillation of crude oil work
- heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top
- vapours from the oil rise through the column
- vapours condense when they become cool enough
- liquids are led out of the column at different heights
properties of smaller hydrocarbons
- weak intermolecular forces
- low boiling points
- they don’t condense, but leave the column as gases
- flammable
- low viscosity
what is fractional distillation used for
to separate different hydrocarbons
properties of larger hydrocarbons
- stronger intermolecular forces
- high boiling point
- they leave the column as hot liquid bitumen
- less flammable
what are useful mixtures called
fractions
what does each fraction of crude oil contain
hydrocarbons with a similar number of carbon atoms
hydrocarbons can undergo incomplete or complete combustion, what does this depend on?
the amount of oxygen available
properties of complete combustion
- carbon dioxide and water are produced
- the maximum amount of energy is given out
combustion equation
hydrocarbon + oxygen → carbon dioxide + water
properties of incomplete combustion
- poor supply of oxygen
- water still produced
- carbon monoxide and carbon dioxide produced
- less energy given out
what is cracking
a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules,
properties of cracking
- the original starting hydrocarbons are alkanes
- the products of cracking include alkanes and alkenes, members of a different homologous series
equation for alkenes
CnH2n
properties of catalytic cracking
- temperature at approximately 550 degrees
- catalyst of zeolite
properties of steam cracking
- high temperatures over 800 degrees
- no catalyst
- steam
why is cracking important
- it helps match the supply of fractions with the demand of them
- It produces alkenes, which are useful as feedstock for the petrochemical industry
why do we use cracking
- There is a high demand for fuels with small molecules and so some
of the products of cracking are useful as fuels. - Alkenes are used to produce polymers and as starting materials for
the production of many other chemicals. - very often, fractional distillation of crude oil produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want.
-Smaller hydrocarbons are more useful as fuels than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand.
properties of alkenes
- saturated (double cc bonds)
- more reactive than alkanes
- can form polymers
- will react with bromine water and turn it from orange/brown to colourless
Examples of things made from crude oil
Plastic, petrol, pharmaceuticals, cosmetic
Where do you find crude oil?
Rock
what is viscosity
tells us the thickness of a fluid - fluids with a high viscosity flow slowly
What does flammability tell us
How easily a hydrocarbon combusts
what do the properties of hydrocarbons depend on
the size of the molecule
examples of things that run on hydrocarbon fuels
should
planes
cars
what happens during combustion
- energy is released
- hydrogen and carbon atoms are oxidised
stages of fractional distillation
- often takes place in large columns which are found in oil refineries
1. crude oil is heated to a very high temperature, causing the crude oil to boil (all of the hydrocarbons evaporate and turn into a gas)
- the crude oil vapour is now fed to the fractional distillation column
- the column is hotter at the bottom and cooler at the top
- hydrocarbons condense when they reach their boiling point, and the liquid fractions are then removed
- the remaining hydrocarbons continue to move up the column, and these condense when they reach their boiling point
where are long chain hydrocarbons removed
from the bottom of the column as they have v high boiling points
where are shorter chain hydrocarbons removed
the top of the column as gases, they do not condense
what is a feedstock
a chemical that’s used to make other chemicals
examples of feedstocks made using fractions
solvents
lubricants
detergents
polymers
why don’t long chain hydrocarbons make good fuels
cos theyre not very flammable
