Organic Chem Flashcards
What is a hydrocarbon
Any compound formed from only hydrogen and carbon atoms
What type of bonds do alkanes have
C-C single bond
What is the formula for alkanes
Cn H2n+2
What is a homologous series
A group of organic compounds that react in a similar way
What are saturated hydrocarbons
When each carbon atom form 4 single covalent bonds
(Alkanes)
List the order of alkanes from 1 carbon atom to 10 carbon atoms
Methane C1 H4
Ethane C2 H6
Propane C3 H8
Butane C4 H10
Pentane C5 H12
Hexane C6 H14
Heptane C7 H16
Octane C8 H18
Nonane C9 H20
Decane C10 H22
Properties of shorter chained hydrocarbons
(Less carbon atoms)
- less viscous (less dense)
- more volatile (can evaporate at lower temperatures)
- so low boiling points
- more flammable
Properties of long chained hydrocarbons
( more carbon atoms)
- viscous (denser)
- not very flammable
- not very volatile (needs higher temperatures to evaporate)
- so high boiling points
Describe the complete combustion of a hydrocarbon
Hydrocarbon + oxygen —> carbon dioxide + water (+ energy)
- both carbon and hydrogen from the hydrocarbon are oxidised
(Gains oxygen, loses electrons) - hydrocarbons are used as fuels due to the amount of energy the release when combusted fully
Balanced equation for the complete combustion of methane
1) CH4 + O2 —> CO2 + H2O
2) CH4 + O2 —> CO2 + 2H2O
3) CH4 + 2O2 —> CO2 + 2H2O
What is crude oil
A fossil fuel formed from the remains of plants and animals, mainly plankton that died millions of years ago and were buried in mud
- over millions of years, with high pressure and temperatures, the remains turned into crude oil
- it can then be drilled up from certain rocks
- a non renewable source (take so long to make, they’re being used up much faster)
- contains a mixture of different hydrocarbons, mostly alkanes
Describe fractional distillation of crude oil
The different compounds in crude oil are separated by fractional distillation
1) the oil is heated into a gas
2) the gas enters a fractionating column
3) in the column there is a temperature gradient ( hotter at the bottom and cooler at the top)
4) the longer the hydrocarbon the higher it’s boiling point so they condense into liquids and are drained out earlier on
5) the shorter hydrocarbons with lower boiling points condense back into a liquid later at the top and are drained out
6) each drained out fraction of the crude oil contains a mixture of hydrocarbons with similar numbers of carbon atoms and boiling points
What are some uses of hydrocarbons from crude oil
- provides fuel for modern transport ( diesel, kerosene, LPG)
- used as feedstock by the petrochemical industry to make polymers, solvents, lubricants and detergents
What is cracking and describe the 2 process
Cracking splits up a long chained hydrocarbon into 2 smaller ones ( an alkane and an alkene)
- short chained hydrocarbons are more flammable so are use better fuels and are high in demand
- cracking is thermal decomposition reaction ( breaking down molecules by heating)
There are 2 methods:
Catalytic cracking-
1) vaporise the hydrocarbon by heating it
2) pass the vapour over a hot powdered aluminum oxide catalyst
3) the long chain hydrocarbons splits into to shorter chained ones
Steam cracking-
1) vaporise the hydrocarbon by heating it
2) mix the vapour with steam and heat at a very high temperature
3) it will split into 2 shorter chained hydrocarbons
What type of bonds do alkenes have
C=C double bond, unsaturated