C7 Flashcards
What are hydrocarbons?
Any compound formed from hydrogen and carbon atoms only.
List the first four alkanes.
Methane
Ethane
Propane
Butane
What is the general formula for alkanes?
CnH2n+2
What are alkanes?
Saturated compounds
No double bonds
What happens as you go down the list of alkanes?
More volatile
More flammable
Increased b.p.
What is the equation for complete combustion?
hydrocarbon + oxygen —-> carbon dioxide + water
How is crude oil formed?
Formed from dead plants and animals then buried in layers of rock and mud
High pressure and temperature forms crude oil
What is the process of fractional distillation?
Feed oil into chamber and heat it until turned into gas
Pass it into a fractionating column that is very hot at the bottom but cooler at the top
Gas will travel up the column until is reaches a fraction that has a lower temp than its boiling point and condenses into a liquid
Why do long chained hydrocarbons condense early on?
They have the highest boiling point
How does the size of long chained hydrocarbons affect its properties?
High boiling points
Low flammability
Low cleanliness of flame (smoky)
High viscosity
How does the size of short chained hydrocarbons affect its properties?
Low boiling points
High flammability
High cleanliness of flame (less smoky)
Low viscosity
What is cracking?
Breaking down longer chains into shorter ones
A thermal decomposition reaction
What is catalytic cracking?
Heat long chained hydrocarbons and vaporise them
Place hydrocarbon vapour over catalyst
As they come into contact they split apart
What is steam cracking?
Mix hydrocarbon vapour with steam
Heat them with very high temperature
Causing them to split
What is the general equation of cracking?
Long chain alkane —-> shorter alkane + alkene
