Organic Chemistry
combined science
- Created by: abbienoice
- Created on: 15-11-20 22:57
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- Organic Chemistry
- Hydrocarbons
- Alkanes
- simplest type of hydrocarbon
- formula = C2H(2n +2)
- the alkanes are a homologous series - group of organic compounds that react in a similar way
- saturated compounds - each carbon atom forms four single covalent bonds
- first four alkanes:
- methane: CH4
- Ethane: C2H6
- Propane: C3H8
- Butane: C4H10
- Hydrocarbon properties change as the chain gets longer
- the shorter the chain the more runny, volatile (lower boiling point), flammable and less viscous (gloopy) the hydrocarbon is
- the properties affect how they're used for fuels
- complete combustion
- occurs when theres plenty of oxygen
- hydrocarbon + oxygen = carbon dioxide + water (+energy)
- during combustion carbon and hydrogen from the hydrocarbon are oxidised
- hydrocarbons are used as fuel due to the amount of energy released when they completely combust
- short - chain hydrocarbons are flammable so make good fuels and are in high demand
- long-chain hydrocarbons are thick, gloopy liquids like tar which aren't useful
- Alkanes
- Fractional Distillation
- crude oil is made
- crude oil is a fossil fuel formed by the remains of plants and animals that dies millions of years ago and were buried in mud
- over millions of years with high temperature and pressure the remains turn into crude oil which can be drilled up from the rocks
- used to separate hydrocarbon fractions
- crude oil is a mixture of lots of different hydrocarbons
- the differnent compounds in crude oil are separated by fractional distillation
- how it works
- 1. the oil is heated until most of it has turned into gas. the gasses enter a fractionating column
- 2. in the column theres a temperature gradient - hot at the bottom and gets cooler as you go up
- 3. the longer hydrocarbons have high boiling points - they condense back into liquids and drain out of the column early on
- 4. the shorter hydrocarbons have lower boiling points - they condense and drain out much later on, near the top of the column
- 5. you end up with crude oil mixture separated out into different fractions - each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms so have similar boiling points
- 4. the shorter hydrocarbons have lower boiling points - they condense and drain out much later on, near the top of the column
- 3. the longer hydrocarbons have high boiling points - they condense back into liquids and drain out of the column early on
- 2. in the column theres a temperature gradient - hot at the bottom and gets cooler as you go up
- diagram*
- 1. the oil is heated until most of it has turned into gas. the gasses enter a fractionating column
- crude oil is made
- Uses and Cracking of Crude Oil
- methods of cracking
- cracking is a thermal decomposition reaction - breaking molecules down by heating them
- 1. heat long-chain hydrocarbons to vaporise them
- 2. then the vapour is passed over a hot powdered aluminum oxide catalyst
- 3. the long-chain molecules split apart on the surface of the specks of catalyst (catalytic cracking)
- 4. you can crack hydrocarbons if you vaporise them, mix them with steam and then heat them to a very high temperature - steam cracking
- 3. the long-chain molecules split apart on the surface of the specks of catalyst (catalytic cracking)
- 2. then the vapour is passed over a hot powdered aluminum oxide catalyst
- uses of crude oil
- oil provides the fuel for most modern transport - diesel oil, kerosene, heavy fuel oil and LGP all come from crude oil
- the petrochemical industry uses some of the hydrocarbons from crude oil as a feedstock to make new compounds for use in things like polymers, solvents, lubricants and detergents
- a lot of longer alkane molecules produced from fractional distillation are turned into smaller, more useful ones by the process of cracking
- as well as alkanes, cracking also produces another type of hydrocarbon, alkenes - more reactive and are used as a starting material when making other compounds/ polymers
- methods of cracking
- test for alkenes
- when orange bromine water is added to an alkane no reaction will happen and the colour will stay the same
- if bromine water is added to an alkene the bromine reacts with the alkene to make a colourless compound
- Hydrocarbons
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