6. Crude OIl and hydrocarbons Flashcards
How is crude oil formed?
Millions of years ago marine (sea) creatures died and fell to the bottom of the oceans.
Layers of other creatures and sediment built up on top.
The layers of died marine creatures were heated and compressed and eventually turned into oil and gas.
What is a definition of crude oil?
Mixture
of mostly hydrocarbons
What is the definition of a hydrocarbon?
A compound that contains hydrogen and carbon atoms only.
What is a homologous series?
A group of different compounds with similar structures or functional groups.
What is the general formula for the alkane homologous series?
CnH2n+2
What can be said about alkanes?
They only contain hydrogen and carbon.
All the bonds are single bonds
They are saturated compounds
They have the general formula CnH2n+2
What are the first for alkanes in the homologous series?
Methane - 1
Ethane - 2
Propane - 3
Butane - 4
What are the molecular, structural and empirical formulae of propane?
molecular - C3H8
structural - CH3Ch2CH3
empirical formulae - C3H8
What are the molecular, structural and empirical formulae of butane?
molecular - C4H10
structural - CH3CH2CH2CH3
empirical formulae - C2H5
What is the name of the process by which crude oil is separated?
Fractional distillation
How does fractional distillation work?
The crude oil is heated (to around 350 oC)
As the mixture rises up the fractionating column it cools.
The longer the carbon chain length the higher the boiling point.
Longer chains condense lower down the fractionating column.
Different fractions of the mixture are isolated/removed/produced at different heights in the fractionating column.
What is the trend of boiling and melting point as chain length increases?
The longer the chain the higher the boiling and melting point.
What is meant by the term chain length?
The number of carbon atoms present in single unbroken line of the hydrocarbon.
Why does the boiling and melting point increase as chain length increases?
There are more intermolecular forces between individual molecules as the chain length increases.
What is the trend of flammability as chain length increases?
Flammability decreases as chain length increases.
What is the trend of viscosity as chain length increases?
Viscosity is the resistance to flow
it increases
What is the trend of cleanliness of the flame as chain length increases?
Cleanliness decreases as chain length increases.
Name some of the key fractions produced from crude oil.
Refinery gas Petrol Kerosene Heavy fuel oil Bitumen
What is cracking?
Where longer chain hydrocarbons are broken down into short chain ones?
What are the conditions for cracking?
Catalytic cracking - catalyst and high temperature
Steam cracking - water vapour and high temperature
Why is cracking useful?
There is more demand for shorter chain hydrocarbons than the percentage of those fractions.
There is less demand for longer chain hydrocarbons than the percentage of those fractions.
Converts less useful into more useful hydrocarbons.
What is produced in cracking?
A variety of saturated (alkanes) and unsaturated (alkenes) hydrocarbons.
What are alkenes?
Hydrocarbons with one or more double carbon bond.
What are unsaturated hydrocarbons?
Hydrocarbons with one or more double or triple carbon bond.
What are the similarities between alkanes and alkenes?
Both:
Hydrocarbons containing hydrogen and carbon only.
Combust to form carbon dioxide and water
What are the differences between alkanes and alkenes?
Alkenes are more reactive
Alkenes are unsaturated; Alkanes are saturated
Alkenes can produce polymers
Alkenes have a double bond; alkanes only have single bonds
