C9.4 - Cracking hydrocarbons Flashcards
What are not in high demand?
Some of the heavier fractions from the fractional distillation of crude oil are not in high demand
Some of the heavier fractions from the fractional distillation of crude oil are not in high demand.
What are the hydrocarbons in them made up of?
The hydrocarbons in some of the heavier fractions from the fractional distillation of crude oil are made up of large molecules
The hydrocarbons in some of the heavier fractions from the fractional distillation of crude oil are made up of large molecules.
What are they?
Some of the heavier fractions from the fractional distillation of crude oil are thick: 1. Liquids Or, 2. Solids with high boiling points
Some of the heavier fractions from the fractional distillation of crude oil are not in high demand.
The hydrocarbons in them are made up of large molecules.
They are thick liquids or solids with high boiling points.
What are they difficult to do?
They:
- Are difficult to vaporise
- Do not burn easily
What is the main demand from crude oil?
The main demand from crude oil is:
- For fuels
- Starting materials (feedstock) for the chemical industry
The main demand from crude oil is for fuels and starting materials (feedstock) for the chemical industry.
Fortunately, what can happen?
Fortunately, the larger, less useful hydrocarbon molecules can be broken down into smaller, more useful ones in a process we call cracking
Cracking
Cracking is the reaction used in the oil industry to break down large hydrocarbons into smaller, more useful ones
Where does cracking take place?
Cracking takes place at an oil refinery in steel vessels called crackers
Cracking takes place at an oil refinery in steel vessels called crackers.
What happens in the cracker?
In the cracker, a heavy fraction distilled from crude oil is heated to vaporise the hydrocarbons
Cracking takes place at an oil refinery in steel vessels called crackers.
In the cracker, a heavy fraction distilled from crude oil is heated to vaporise the hydrocarbons.
What happens to the vapour?
The vapour is then either:
1. Passed over a hot catalyst
Or,
2. Mixed with steam and heated to a very high temperature
Hydrocarbons are cracked as what take place?
Hydrocarbons are cracked as thermal decomposition reactions take place
Thermal decomposition
Thermal decomposition is the breakdown of a compound by heating it
Hydrocarbons are cracked as thermal decomposition reactions take place.
What do the large molecules split apart to form?
The large molecules split apart to form smaller, more useful ones
In an oil refinery, huge crackers are used to break down large hydrocarbon into smaller, more useful ones.
What does the petrochemical industry do?
The petrochemical industry source the chemicals used to make products such as:
- Solvents
- Lubricants
- Polymers
- Detergents
- The fuels that modern life depends on
What is decane?
Decane is a medium-sized alkane molecule
Decane is a medium-sized alkane molecule.
What happens when it is heated to 500 degrees Celsius with a catalyst?
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down.
What is 1 of the molecules produced?
1 of the molecules produced is pentane
What is pentane used in?
Pentane is used in petrol
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down.
1 of the molecules produced is pentane.
What are also made?
- Propene
- Ethene
are also made
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down.
1 of the molecules produced is pentane.
Propene and ethene are also made.
What can the chemical industry use propene and ethene to do?
The chemical industry can use propene and ethene to produce:
- Polymers
- Other chemicals
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down.
1 of the molecules produced is pentane.
Propene and ethene are also made.
What is this cracking reaction an example of?
This cracking reaction is an example of thermal decomposition
In a saturated hydrocarbon, what does its molecules have?
In a saturated hydrocarbon, its molecules have as much hydrogen as possible in them
Alkene
Alkenes are unsaturated hydrocarbons which contains a carbon-carbon double bond
Double bond
A double bond is a covalent bond made by the sharing of 2 pairs of electrons
What do unsaturated compounds contain?
Unsaturated compounds contain at least 1 double bond between their carbon atoms
Unsaturated compounds contain at least 1 double bond between their carbon atoms.
As carbon atoms form 4 covalent bonds, what does it mean?
As carbon atoms form 4 covalent bonds, it means that the unsaturated alkene molecules have 2 fewer hydrogen atoms in their molecules than the saturated alkane molecules with the same number of carbon atoms
The apparatus for cracking medicinal paraffin
The apparatus for cracking medicinal paraffin is:
- Gaseous product
- Water
- Safety valve
- Delivery tube
- Broken pot (catalyst)
- Ceramic wool soaked in medicinal paraffin
- (Heat)
What do the tests on the gaseous products from the experiment for cracking medicinal paraffin show?
The tests on the gaseous products from the experiment for cracking medicinal paraffin show that alkenes:
- Burn in air, but not as well as equivalent small alkanes which are used as fuels
- React with bromine water, which is orange in colour, decolourising it
What are alkenes generally?
Alkenes are generally more reactive than alkanes
Alkenes are generally more reactive than alkanes.
What is used as a test to see if an organic compound is unsaturated, like the alkenes with their C=C double bond?
The reaction with bromine water is used as a test to see if an organic compound is unsaturated, like the alkenes with their C=C double bond
Alkenes are generally more reactive than alkanes.
The reaction with bromine water is used as a test to see if an organic compound is unsaturated, like the alkenes with their C=C double bond.
What is a positive test for an unsaturated hydrocarbon?
A positive test for an unsaturated hydrocarbon is that it turns orange bromine water colourless
The reaction with bromine water is used as a test to see if an organic compound is unsaturated, like the alkenes with their C=C double bond, and to also distinguish between what?
The reaction with bromine water is used as a test to see if an organic compound is unsaturated (like the alkenes with their C=C double bond) and to also distinguish between an:
- Alkene
- Alkane
Why can you use the reaction with bromine water as a test to distinguish between an alkene and an alkane?
You can use the reaction with bromine water as a test to distinguish between an alkene and an alkane, because alkanes do not react with bromine water, whereas alkanes turn orange bromine water colourless
Some of the heavier fractions from the fractional distillation of crude oil are not in high demand.
The hydrocarbons in them are made up of large molecules.
They are thick liquids or solids with high boiling points.
They are difficult to vaporise and do not burn easily, so they are what?
They:
1. Are difficult to vaporise
2. Do not burn easily
,so they are poor fuels
Some of the heavier fractions from the fractional distillation of crude oil are not in high demand.
The hydrocarbons in them are made up of large molecules.
They are thick liquids or solids with high boiling points.
They are difficult to vaporise and do not burn easily, so they are poor fuels, although they do have what?
They:
1. Are difficult to vaporise
2. Do not burn easily
,so they are poor fuels, although they do have their uses
When decane is heated to 500 degrees Celsius with a catalyst, it breaks down.
1 of the molecules produced is pentane.
Propene and ethene are also made.
The chemical industry can use propene and ethene to produce polymers and other chemicals, such as what?
The chemical industry can use propene and ethene to produce:
- Polymers
- Other chemicals, such as solvents
The general formula for alkenes
The general formula for alkenes is CnH2n
