Organic chemistry Flashcards
What is an Alkane and state the general formula
saturated hydrocarbon with a single carbon bond
Cn H2n+2
What is a hydrocarbon?
Molecules made up of only hydrogen and carbon atoms
How is crude oil formed?
Dead sea animals that don’t decompose and turn into kerogen. kerogen is then turned into crude oil.
What are the properties of hydrocarbons?
- Boiling points and viscosity of hydrocarbons increase as the molecules get bigger (because the intermolecular forces become larger as the molecules become bigger)
- Volatility (how easily a liquid vaporises) and Flammability of the fuels decrease as the molecules get bigger
What is fractional distillation
The process where crude oil is refined
Describe the process of fractional distillation
Crude oil is heated
substances in crude oil evaporate into fractions
columns are hotter on the bottom and colder at the top
substances condense at their boiling point
What is complete combustion of alkanes?
When carbon and hydrogen become oxidised to become carbon dioxide and water, as the alkanes are burnt in excess oxygen
alkane + oxygen —> carbon dioxide + water
What is incomplete combustion?
When alkanes are burnt in a limited supply of oxygen, forming carbon monoxide
Alkane + oxygen —-> carbon monoxide + water
What are pollutants from burning fuels?
Carbon dioxide contributes to climate change
carbon monoxide - toxic gas
sodium dioxide - acid rain
soot - global dimming
What is an alkene and state the general formula
An unsaturated hydrocarbon with a double carbon bond
Cn H2n
Describe the test for alkenes
Bromine water is added to an orange solution. If the solution becomes colourless, then it is an alkene, and the new hydrocarbon is an alkane
What is cracking?
the breakdown of large hydrocarbons into smaller, more useful hydrocarbons
What are the conditions of cracking?
high temp + steam
or
high temp + catalyst
What are the uses of cracking products
There is a high demand for fuels with small molecules so some of the products of cracking are useful as fuels.
* Alkenes are used to produce polymers and as starting materials for the production of many other chemicals
How do polymers form?
When alkenes (double bond) open up to form long chains made from monomers.
requires a catalyst and pressure
What are the two types of polymers and their properties?
Low density -
made from high pressure and traces of oxygen. (have a branched structure)
high density -
catalyst = 50 degrees
polymer chains are straighter and can be more tightly packed.
What is a thermosoftening polymer and describe its structure.
a polymer that melts when heated but turns into a solid at room temperature. has weak intermolecular forces between polymer chains, making it easily melted, as the intermolecular forces are easily broken
What is a thermosetting polymer, and describe its structure
a polymer that doesn’t melt when heated. this is because the crosslinks between the polymer chains have strong covalent bonds, resulting in high temperatures needed to break the bonds
