Organic Chemistry Flashcards
What is a hydrocarbon
Any compound formed from carbon and hydrogen atoms only
What are alkanes
- formula CnH2n+2
- in homologous series
- saturated compounds
What’s the homologous series
A group of organic compounds that react in a similar way
What is a saturated compound
Means that each carbon forms 4 single covalent bonds
What are the 4 first alkanes
- methane CH4
- ethane C2H6
- propane C3H8
- butane C4H10
How does length of carbon affect the properties of hydrocarbons
- shorter carbon chain: more runny, less viscous(gloopy)
- shorter carbon chain: more volatile (lower boiling point)
- shorter carbon chain: more flammable
Word equation for complete combustion of a hydrocarbon
Hydrocarbon + oxygen — carbon dioxide + water + (energy)
Important things that happens during combustion of hydrocarbon
- both carbon and hydrogen atoms are oxidised
- hydrocarbons are used as fuels due to the amount of energy realised wen they combust completely
What is crude oil
- fossil fuel
- can be used to make loads of useful things such as fuels
How is crude oil formed
- formed from remains of plants and animals, mainly plankton that died millions of years ago and were buried in mud
- over millions of years with high temperature and pressure, the remains turn to crude oil
- it can be drilled up from the rocks where its found
How does fractional distillation of crude oil work
- Oil is heated until most of it has turned into gas. The gases enter a fractionating column
- In the column theres a temperature gradient (hot at bottom and gets cooler as you go up)
- The longer hydrocarbons have high boiling points, they condense back into liquids and drain out of the column early on when they’re near the bottom.
- The shorter hydrocarbons have lower boiling points. They condense and drain out much later on, near to the top of the column where its cooler
- You end up with crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that al contain a similar number of carbon atoms, so have similar boiling points
Order of different fuels produce from crude oil in a fractionating column
From bottom to top (hot to cold)
- bitumen
- heavy fuel oil
- diesel oil
- kerosene
- petrol
- LPG
What is LPG used for
- liquified petroleum gas
- contains mainly propane and butane
What is petrol used for
Cars
What is kerosene used for
Planes
What is diesel used for
Lorries
What is heavy fuel oil used for
- heating oil
- fuel oil
- lubricating oil
Important uses of crude oil in modern life
- provides fuel for most modern transport
- petrochemical industry uses crude oil as feedstock to make new compounds for use in things like polymers, solvents, lubricants and detergents
What is an organic compound
Compounds containing carbon atoms
Why do we get such a large variety in products from organic compounds
- carbon atoms can bond together to form different group called homologous series
- these groups contain similar compounds with many properties in common
Bromine water test for alkenes
- If it’s added to an alkene the bromine reacts with the alkene to make a colourless compound - so the bromine water is decolourised
What is cracking
- splitting of long-chain hydrocarbons into smaller more useful alkane or alkene molecules
What are alkenes
- a lot more reactive than alkanes
- used a a starting material when making other compounds and can be used to make polymers
- CnH2n
Catalytic cracking
- Heat long-chain hydrocarbons to vaporise them
- Then the vapour is passed over a hot powdered aluminium oxide catalyst
- The long-chain molecules split apart on the surface of the specks of catalyst
