Alkanes Flashcards
What are crude oils? (3)
A finite source found in rocks
The remains of ancient biomass consisting of mainly plankton that was buried in mud
A mixture of a very large number of compounds (mostly hydrocarbons)
What are alkanes?
They are saturated hydrocarbons meaning they contain carbon and hydrogen atoms only as well as only containing single bonds
Describe the fractional distillation process (5)
Crude oil is heated to vaporise it
The vapour is passed into the column
There is a temperature gradient so the column is hot at the top and cooler at the bottom
Fractions are separated due to their different boiling points so they condense at different levels and are removed
Fractions with low boiling points are collected at the top whereas hotter ones are collected at the bottom
Name the order of fractions from the top of the column to the bottom (8)
Refinery gas
Gasoline
Naptha
Kerosene
Diesel oil
Lubricating oil
Fuel oil
Bitumen
Define cracking
A process where long chain hydrocarbons are broken into smaller chain hydrocarbons
Why does cracking require high temperatures
A lot of energy is required to break the strong C-C bonds
What are 2 conditions for thermal cracking
What are the products (2)
High temperatures of around 1200K
High pressures of around 7000kPa
A large proportion of alkenes and a lower proportion of branched alkanes
Define thermal cracking
A process used to split long chain alkanes into shorter alkanes and alkenes
Define catalytic cracking
A process used to split long chain alkanes into shorter alkanes and alkenes
What are 3 conditions for catalytic cracking
What are the products (2)
Relatively low temperatures (700K)
Requires only a slight pressure
A zeolite catalyst
A large proportion of branched alkanes and arenes
What is thermal cracking used for and what is the mechanism
Polymers
Free radical
What is catalytic cracking used for and what is the mechanism
Motor fuels
Carbocation
What type of process is the combustion of alkanes
What does this make them good for and why
Highly exothermic process
Good fuels because they release relatively large amounts of energy per gram of fuel
How do you write balanced combustion equations
Balance in alphabetical order
Make sure the moles of the fuel remains 1
What products can be formed in incomplete combustion
Carbon monoxide or carbon and water
How does the wording of the question tell you which pollutant is formed in incomplete combustion
CO = gaseous pollutant
C = solid pollutant
Which alkanes are used as fuels in internal combustion engines
Those with the chain lengths of 5 to 10
How is nitrogen monoxide formed in IC engines and why
What is the equation to show this
Nitrogen and Oxygen react to form NO
Because the temperatures in the engine can reach over 2000 degrees C
N2 + 02 = 2NO
What is the equation for when nitrogen monoxide reacts more to form nitrogen dioxide
2NO + O2 = 2NOz
How does nitrogen dioxide form acid rain
What is the equation for it
It reacts with rain water and more oxygen to form nitric acid which contributes to acid rain
4NOz + 2HzO + Oz = 4HNO3
What is a catalytic converter used for
It is used to transform pollutant gases in a cars exhaust engine into harmless gases
What are 3 gases that go into catalytic converters from the engine
Carbon monoxide
Nitrogen oxides
Unburnt hydrocarbons
What is the catalyst in the catalytic converters
Rhodium
What are 3 exhaust gases from catalytic converters
Carbon dioxide
Nitrogen
Carbon dioxide + water
