Organic chemistry Flashcards
Define crude oil
The remains of an ancient biomass consisting mainly of plankton that was burried in mud
What are most of the compounds in crude oil called?
Hydrocarbons
Define hydrocarbons
Molecules made up of hydrogyn and carbon atoms only
What are most of the hydrocarbons in crude oil called?
Alkanes
What is the general formula for alkanes
C n H 2n+2
What are the first four members of the alkanes called?
Methane, ethane, propane and brutane
My exquisite popcorn burnt
What type of bond do alkanes have between the carbon atoms?
Single covalent bond
State the formulas for all 4 alkanes
Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10
What is fractional distillation used for in terms of crude oil?
The hydrocarbons in crude oil may be seperated into fractions, each of which contains molecules with a similar number of carbon atoms
Give examples of the fuels produced from fractions
Petrol
Diesel oil
Kerosene
Heavy fuel oil
Liquefied petroleum gases
Give examples of the useful materials in the petrochemical industry produced from fractions
Solvents
Lubricants
Polymers
Detergents
Define viscosity
The thickness of a liquid
How does the boiling point of hydrocarbons change with increasing molecular size?
The larger the size, the higher the boiling point
How does the viscosity of hydrocarbons change with increasing molecular size?
The larger the size, the higher the viscosity
How does the flammability of hydrocarbons change with increasing molecular size?
The larger the size, the less the flammability
What does the complete combustion of a hydrocarbon produce?
Carbon dioxide and water
Why are hydrocarbons cracked?
To produce smaller, more useful molecules
E.g. to make fuels as longer chains aren’t flammable
Describe the conditions used for catalytic cracking
Uses high temperature
Uses a catalyst to speed up the reaction
Describe the conditions used for steam cracking
Uses high temperature
Uses steam
Define alkene
A hydrocarbon which is a product of cracking
Compare alkanes with alkenes
Alkanes have a single covalent bond between 2 carbon atoms whereas alkenes of a double covalent bond
Alkenes are more reactive than alkanes
Describe the test for alkenes
Alkenes react with bromine water and turn colourless to indicate the presence of alkenes
Explain the usefulness of cracking
There is a high demand for fuels with small molecules and so some
of the products of cracking are useful as fuels
What are alkenes used to do?
Chemicals called polymers
Used as the starting material for other useful chemicals
Explain how fractional distillation works in terms of evaporation and condensation
The oil is heated in the fractionating column and the oil evaporates
and condenses at a number of different temperatures
The many hydrocarbons in crude oil can be separated into fractions
each of which contains molecules with a similar number of carbon
atoms
The fractionating column works continuously, heated crude oil is
piped in at the bottom. The vaporised oil evaporates and rises up the
column and the various fractions are constantly tapped off at the
different levels where they condense
Alkanes have _________ bonds
single
