C7 - Organic Chemsitry Flashcards
What are hydrocarbons
Only contain hydrogen and carbon atoms
What are Alkanes
Alkanes have all C-C single bonds Saturated compounds - each carbon atom forms 4 single covalent bonds They’re the simplest hydrocarbon. Have a general formula of CnH2n+2 Alkanes are a homologous series
What’s a homologous series
Group of organic compounds that react in a similar way
Give example of Alkanes
Methane CH4
Ethane C2H8
Propane C3H8
Butane C4H8
How do hydrocarbon properties change as chain gets longer
Shorter carbon chain - more runny hydrocarbons - less viscous
More volatile - lower boiling points and more flammable
What is complete combustion
Plenty of oxygen - releases lots of energy
Hydrocarbon + oxygen -> carbon dioxide + water (+energy)
Both carbon and hydrocarbon oxidised
Why are hydrocarbons used as fuels
Used as fuels as they release lots of energy
What is fractional distillation used for
To separate hydrocarbon fractions
Name the fractions of crude oil and their uses
Gas - cookers Petrol - car fuel Kerosene - airplane fuels Diesel oil - truck Heavy fuel oil - heating oil, lubricating oil Bitumen - layering roads
What is crude oil
A mixture of hydrocarbons
Describe process of fractional distillation of crude oil
Oil heated until most turns to gas
Gas enters fractionating column
Temperature gradient in column (hot at bottom, cool at top)
Longer hydrocarbons have higher boiling points
Condensed into liquids and drain out of column earlier on (near bottom)
Shorter hydrocarbons have lower boiling points - condensed towards top
You end up with crude oil mixture separated into different fractions
What is the petrochemical industry
Use hydrocarbons from crude oil as feed stock to make new compounds for use in things like polymers, solvent, lubricants
What are products from crude oil
All organic compounds (compounds with carbon atoms)
Range of products as carbon atoms can bond together to form homologous series - both Alkanes and Alkanes
What is cracking
Splitting up long chain hydrocarbons
Why is cracking used
Shirt chain - flammable - good fuel
Long chain - thick liquid which isn’t useful
So long chain turned into smaller ones so they’re useful as fuels
What does cracking produce
Alkanes and Alkenes
What are alkenes
More reactive - used as starting material when making other compounds that can be used to make polymers
Possess one or more double C-C bond
General formula of CnC2n
How can bromine water test for alkenes
Bromine water into Alkanes - stay bright orange
Bromine water into alkene - colourless compound
What are the different methods of cracking
Thermal decomposition reaction - breaking molecules down through heating
1. Heat long chain molecules to vaporise them
2. Vapour passed over hot powered Aluminium oxide catalyst
3. Long chain molecules split apart on surface of specks of catalyst - ‘catalyst cracking’
Steam cracking - heat and vaporise - mix with steam and heat to high temperature
Properties of homologous series
Same general formula
Increasing chain length - higher boiling points
First three alkenes formula
Ethene - C2H4
Propene- C3H6
Butene - C4H8
