C9 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
Cirde 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 and 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 CH4
Ethane C2H6
Propane C3H8
Butane C4H10
How is crude oil seperated
Fractional distillation
Give examples of the uses of the fractions derived from seperating crude oil
Petrol, kerosene, diesel oil, heavy fuel oil, liquified petroleum gas
It can also be used as feedstock such as solvents, lubricants, polymers, detergents.
How does size of the hydrocarbon effect: boiling point, viscosity and flammability
Short chain Lower BP 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 liquids drained off
(There is a temperature graduent in the column (hotter at the bottom and cooler at the top)) -CB
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 chains condense lower down, shortest chain stay as gases
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 for cracking
Catalytic cracking:
Vaporise hydrocarbons are passed over a hot powdered 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 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 starting materials for the production of many other chemicals
