C9 Crude Oil And Fuels Flashcards
What is crude oil
Crude oil is a finite resource found in rocks. Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
What is the composition of crude oil
Crude oil is a mixture of a very large number of compounds. Most of the compounds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only.
What is a hydrocarbon
A chemical compound made up of hydrogen ans carbon atoms only
What is the general formula for alkanes
C(n) H(2n+2)
What are the first 4 members of the alkanes
Methane: C H4
Ethane: C2 H6
Propane: C3 H8
Butane: C4 H10
How is crude oil seperated
Fractional distillation
Give examples of the uses of fractions dierived from seperating crude oil
Petrol, kerosene, diesel oil, heavy fuel oil, liquified petroleum gas
How does the size of the hydrocarbon effect: boiling point, viscosity and flammability
Short chain: Lower boiling point Low viscosity Higher flammability Long chain: Higher boiling point High viscosity Lower flammability ( burns with smokier flame )
How does fractional distillation work
Crude oil is heated until most has turned to gas
Gases enter fractionating column and liquid drains off
The gases rise and as they rise the temperature cools
Once the gases reach a fraction cool enough, they condense and are drained off
The longer chain condense lower down, shortest chains stay as gases
What is the general formula for the complete combustion of hydrocarbons
Hydrocarbon + oxygen = carbon dioxide + water
What is cracking?
Longer, less useful hydrocarbons can be split up to form shorter hydrocarbons which are more useful for fuel, it also produces alkenes
What are the methods of cracking?
Catalytic cracking:
Vaporised hydrocarbons are passed over a hot powered aluminium oxide catalyst. The longer chains are split apart on the surface of the catalyst
Steam cracking:
Vaporised hydrocarbons are mixed with steam and heated to a high temperature to crack them
Shat are the products of cracking
Shorter alkanes
Alkenes
What is the test for an alkene
They react with bromine water and turn it from yellow to colourless
Why do we crack hydrocarbons
There is a high demand for fuels with small molecules and 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.
