Organic Chemistry Flashcards
What is a hydrocarbon? What is crude oil?
A compound containing hydrogen and carbon only. Crude oil is a mixture of hydrocarbons
What is a fraction in crude oil?
A part of the mixture with a similar boiling point
What are properties of hydrocarbons if they have longer chains?
- The higher the boiling point
- The higher the viscosity
- The lower the flammability
Why are short chain hydrocarbons more expensive than long chain hydrocarbons?
They are more useful as fuel since they are more flammable
Describe how crude oil is formed
- Millions of years ago when plants and animals which lived in the sea died and fell to the bottom
- Layers of sediment then formed on top of them and their shells and skeletons formed limestone
- The soft tissue was gradually changed by high temperatures and pressures into crude oil
How are hydrocarbons in crude oil separated?
Fractional distillation (physical process)
Describe how fractional distillation works
- The crude oil is heated until it turns into a gas
- Then as it enters the fractional column the gas rises
- However each different fraction has a different boiling point
- Therefore as the gas rises up in the fractioning column, which is gradually cooler, each fraction condenses back into a liquid at different points (where the temperature is lower than their boiling point), separating the crude oil into different fractions
What are the differences between the lab and industrial process of separating crude oil?
LAB -start with a liquid and vaporises one by one and uses -bunsen burner -uses mineral wool -one delivery tube IND: -vapours all (liquid bit bitumen is drained off at the bottom) and then condenses one by one at different temperatures -uses a furnace to heat -no mineral wool -separate tubes for each fraction
How are refinery gases uses (top)?
- Bottles gas
- Domestic heating
- Used in pottery and glass manufacture
How is gasoline (petrol) (second from top) used?
-Fuel for cars
How is kerosine (third from top) used?
- Fuel for jet aircraft
- Domestic heating oil
- ‘Paraffin’ for small heater and lamps
How is diesel oil (gas oil) (fourth from top) used?
- Fuel for buses, lorries, some cars
- Some is also cracked to make other organic chemicals and more petrol
How is fuel oil (fifth from top) used?
- Domestic central heating
- Fuel for big ships
How bitumen used (bottom)?
- Road surfacing
- Asphalt for roofs
What is the order of fractions?
Top to bottom
- Refinery gases
- Gasoline (petrol)
- (Naphtha used in chemical industry as starting material to make plastics, dyes, drugs, explosives, paints)
- Kerosine
- Diesel oil
- Fuel oil
- Bitumen
What are bubble caps in the fractioning column used for?
To stop the separated liquids from running back down the column and remixing
What is a fraction?
A mixture of hydrocarbons with similar boiling points
Why does boiling point increase/become more volatile the longer the chain?
As the chain is bigger, (there is a greater number of) intermolecular attractions (forces) increase and so more heat (energy is needed to overcome them) is needed to break these stronger attractions to produce the widely separated molecules in the gas
Why do the liquids become more viscous the longer the chain?
The more contact points so it is harder for them to slide over each other
Describe Alkanes
They are the simplest homologous series of organic compounds
What is a homologous series?
Compounds in a homologous series have similar chemical properties and show a trend in physical properties
How do you name isomers?
- Count longest side c chain
- Identify side chain
- Identify position of side chains
Describe isomers
They have the same molecular formula but different structural formula
Why do branch chains have lower boiling points than straight chains?
Because there are fewer points of contact with each other and so there are weaker intermolecular forces
Why are alkanes saturated?
Because they contain only single carbon carbon bonds
Why are alkenes unsaturated?
Because they contain a double carbon carbon bond
Why are alkanes unreactive and alkenes more reactive?
- They have a strong carbon-hydrogen bond
- Alkenes are more reactive because they have a double bond which is weaker and hence easier to break