F322-Fuels Flashcards
What is fractional distillation?
A method of separating the crude oil mixture into fractions according to their boiling points
What is volatility?
How easily it turns into a gas
Where do the more volatile components with lower boiling points go in fractional distillation?
They rise to the top of the fractionating column
What can hydrocarbons obtained from crude oil be used directly as?
Fuels or as feedstock for processing into petrochemicals
Give a use for propane
Bottled gas
What 1-4 carbon alkanes used for?
Bottled gas
What are carbon 5-7 alkanes used for?
Petrol
What are carbon 6-10 carbon alkanes used for?
Making petrochemicals
What 3 points make a good fuel?
~volatile
~easy to ignite
~burns completely in air(no soot)
What does catalytic cracking do?
It converts long-chain hydrocarbons into more useful alkanes and alkenes using heat and a catalyst
Give an example of cracking
C6H14 > C4H10 + C2H4
Suggest 2 reasons why oil companies use catalysts
1- catalysts speed up the reaction without being consumed
2- using a catalyst saves money for the companies as they are cheaper to run and allows a lower temperature to be used so less fuel is needed
What does Isomerisation do? State conditions needed
Converts straight chain alkanes into branched alkanes.
Conditions = high temp & platinum catalyst
What does reforming do? State conditions needed.
Converts straight chain alkanes into cyclic alkanes and arenes.
Conditions = high temp & platinum catalyst
Why are branched alkanes and cyclic hydrocarbons used in petrol?
To promote efficient combustion and prevent pre-ignition
What is used to grade the quality of petrol?
Research octane number (RON)
What does an alkane that burns efficiently have?
A high octane number
Describe the effect if chain length on octane number
The longer the chain length, the lower the octane number
Describe the effect of chain branching on octane number
The more branching, the higher the octane number
Why is 2-methylpentane more volatile than hexane?
The branching of 2-methylpentane makes it more volatile than hexane as the branches means there is less surface contact, the van der Waals’ forces are weaker so less energy is needed to break them. This means it can turn into a gas more easily
What does burning alkanes in a limited supply of oxygen result in?
Incomplete combustion
Write an equation for the formation of NO
N2 + O2 > 2NO
What is complete combustion?
When alkanes burn in a plentiful supply of oxygen to form carbon dioxide and water
Write an equation for the complete combustion of hexane
C6H14 + 9.5 O2 > 6CO2 + 7H2O
What is incomplete combustion?
When alkanes burn in a limited supply of oxygen to form carbon monoxide or soot rather than carbon dioxide
Write an equation to show the incomplete combustion of hexane
C6H14 + 6.5 O2 > 6CO + 7H2O
What is catalytic cracking?
When long-chain hydrocarbons are broken down into a mixture of shorter-chain alkanes and alkenes.
Write an equation to show the cracking of decane
C10H22 > C8H18 + C2H4
What contributes to global warming?
The absorption of infra-red radiation by gas molecules in the atmosphere
Why are carbon dioxide and methane known as greenhouse gases?
They absorb heat energy to warm up the atmosphere
What happens to the molecules when they absorb infra-red radiation?
The bonds vibrate and stretch when they absorb energy
What is the ‘greenhouse effect’ of a given gas dependent on?
1-it’s atmospheric concentration
2-it’s ability to absorb infrared radiation
Why are scientists more concerned about carbon dioxide as a greenhouse gas than methane?
Because the concentration is higher
Why is it important to control global warming?
Because if not: ~rising sea level ~climate change ~loss of natural habitats ~melting of polar ice
Name and explain a new technology scientists are developing to minimise climate change.
Carbon capture and storage (CCS)
Involves the removal of waste carbon dioxide before it enters the atmosphere.
a) CO2 can be turned into liquid and injected deep in the oceans or stored geological formations.
b) waste CO2 can be reacted with metal oxides to form stable carbonate minerals.
Explain why the incomplete combustion is potentially dangerous?
Because carbon monoxide binds to haemoglobin better than oxygen does so results in death.
What information are scientists providing to change opinions?
They are providing scientific evidence to governments to verify that global warming is taking place.
