Unit 7- Organic Chemistry Flashcards
What is a hydrocarbon
Any compound that is formed from carbon and hydrogen atoms only
What is crude oil
-finite resource found in rocks
-it is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
-it is a mixture of a very large number of compounds
-Most of the compounds in crude oil are hydrocarbons called alkanes
General formula for alkanes are
Cn H2n+2
What is an alkane
-all have C-C single bond and contain H-H single bonds
-they are a homologous series
-saturated compounds (linked by single bonds)
-the first four are methane , ethane, propane and butane
What is a homologous series
A group of organic compounds that react in the same way
How does properties of hydrocarbons vary with size of their carbon chain
-the shorter the carbon chain the less viscous
-the shorter the carbon chain the more volatile (lower boiling point)
-shorter the carbon chain the more flammable
Word equation for complete combustion
Hydrocarbons + oxygen —> carbon dioxide + water + (energy )
What occurs during complete combustion
-releases a lot of energy
-the carbon and hydrogen in the fuels are oxidised (gain of oxygen)
What does crude oil produce
petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases
What is produced by the petrochemical industry
solvents, lubricants, polymers, detergents
What is fractional distillation
-many hydrocarbons in crude oil can be separated into fractions, each of which contains molecules with a similar number of carbon atoms
-The fractions can be processed to produce fuels and feedstock for the petrochemical industry
Process of fractional distillation
-oil is heated until most of it has turned into a gas
- the gas enters a fractionating column
-in the column there is a temperature gradient (hot at the bottom and gets cooler as you go up)
-the longer hydrocarbons have higher boiling points so they condense back into liquids and drain out of the column near the bottom
-the shorter hydrocarbon have lower boiling points they condense and drain out near the top of the column
-you end up with crude oil separated out into different fractions that all contain similar no of carbon atoms so similar boiling points
What is cracking
-Hydrocarbons are broken down (cracked) to produce smaller more useful molecules
-it can be done by various methods including catalytic cracking and steam cracking
Uses for crude oil in modern life
For modern transport =Petrol,diesel oil! kerosene! liquefied petroleum
Petrochemical industry =solvents , lubricants, polymers
Process of cracking (both of them)
It is a Thermal decomposition reaction.
Catalytic cracking :
-heat long chain hydrocarbons to vaporise them
-then the vapour can be passed over a hot powdered aluminium oxide catalyst
-the long chain molecules split apart on the surface of the speak of the catalyst
Or steam cracking :
-if you vaporise them, mix them with steam and then heat them to a very high temperatures
Why are alkanes often used as fuels in
As they release energy when burnt
General formula for alkenes
Cn H2n
What is a alkene
-all have C=C (carbon double bond)
-carbon double bond means that alkenes have two fewer hydrogens this makes them unsaturated
-more reactive than alkanes
What are the first 4 alkanes
-methane (CH4)
-Ethane(C2H6)
-butane (C3H8)
-propane (C4H10)
What are the first four alkenes
-Ethene (C2H4)
-propene (C3H6)
-butene (C4H8)
-pentane (C5H10)
Incomplete combustion of alkenes word equation
-burn with a smoky flame
Alkene + oxygen —> carbon + carbon monoxide + carbon dioxide + water (+energy)
What is the addition of hydrogen known as
Hydrogenation