Crude oils and fuels (7.1) (M) Flashcards
What type of resource is crude oil?
A finite resource
Where is crude oil found?
in rocks
What is physically crude oil?
Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
+ include ‘a finite resource found in rocks’ and maybe chemical composition
What is the chemical composition of crude oil?
a mixture of a very large number of compounds
What are most of the oils found in crude oil?
hydrocarbons
What are hydrocarbons?
molecules made up of hydrogen and carbon atoms only
What makes up most of the hydrocarbons found in crude oil?
alkanes
What is the general formula for the homologous series of alkanes?
CnH2n+2
What are the first four members of the alkanes?
methane (CH4), ethane (C2H6), propane (C3H8) and butane (C4H10)
What are the two forms alkanes can be represented in? (formula and diagram)
example for ethane
What are many hydrocarbons in crude oil may be separated into?
fractions
What are fractions?
mixtures of hydrocarbons which contain molecules with a similar number of carbon atoms, separated by fractional distillation
What can fractions be processed to do?
produce fuels and feedstock for the petrochemical industry
5 needed
What are some fuels produced from crude oil we depend our modern lifestyle on?
- petrol
- diesel oil
- kerosene (jet fuel)
- heavy fuel oil
- liquefied petroleum gases
Many useful materials on which modern life depends are produced by what industry?
the petrochemical industry
4 needed
What are examples of useful materials on which modern life depends produced the petrochemical industry
solvents, lubricants, polymers, detergents
The vast array of natural and synthetic carbon compounds occur due to what?
the ability of carbon atoms to form families of similar compounds
Explain how fractional distillation separates crude oil into fractions
- Crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top
- The crude oil is heated
- to evaporate the hydrocarbons
- vapours from the oil rise through the column
- hydrocarbons condense when cool enough
- at their different boiling points
- and collected as fractions (each fraction has a different boiling point based on the length of the hydrocarbon chain/molecule)
- smaller hydrocarbons collected at top, larger hydrocarbons collected at bottom (longest ones i.e. bitumen will not evaporate and is collected as residue)
How do smaller hydrocarbons compare with large hydrocarbons in terms of the properties: boiling point, flammability, viscocity and smokiness of flame?
Smaller hydrocarbons:
- have lower boiling points
- are more flammable
- have a lower viscosity
- the flame is also cleaner (less smoky) - due to higher flammability
What does the combustion of hydrocarbon fuels release?
energy
What happens to the carbon and hydrogen in the fuels (hydrocarbons) during combustion?
They are oxidised (gain of oxygen)
What does the complete combustion of a hydrocarbon produce?
carbon dioxide and water
What does combustion require?
heat
What is the formula for the complete combustion of ethene?
C2H4 + 3O2 ⇢ 2CO2 + 2H2O
What is cracking?
the process of breaking down larger, less useful hydrocarbons to produce smaller, more useful molecules
What are 2 forms of cracking?
catalytic cracking and steam cracking
What are the conditions required for catalytic cracking?
passing large hydrocarbon vapour (may be soaked in ceramic wool) over a hot catalyst (e.g. porous broken pot).
Heat to very high temperature
only bold is necessary
What are the conditions required for steam cracking?
mixing large hydrocarbon vapour with steam and heating to a very high temperature
only bold is necessary
What are the products of cracking?
alkanes (saturated) and alkenes (unsaturated)
What are more reactive, alkanes or alkenes?
alkenes
How do you test for an alkene?
Add orange bromine water to hydrocarbon, if it turns colourless, an alkene is present
(alkenes react with bromine water, alkanes do not)
Which fuels are in high demand?
small molecules (hydrocarbons)
crude oil contains too many large hydrocarbons and not enough smaller, more useful ones
Some of the products of cracking are used as (…) as small molecules (hydrocarbons) are in high demand
fuels
2 needed
What are the uses of alkenes?
- produce polymers
- used as starting materials for the production of many other chemicals
What is the reaction for the cracking of C6H14?
C6H14 ⇢ C4H10 + C2H4
Alkenes turn bromine water from (…) to (…)
brown
colourless
- so bromine water is test for alkenes (no affect on alkanes)*
- as alkenes react with bromine by breaking their carbon-carbon double bond*
What are two conditions needed for cracking?
- High temperature
- Catalyst or steam
Why does cracking take place?
To obtain smaller hydrocarbon molecules
that are in demand
and are more useful/are used as fuels
After cracking, a black substance is produced on the bottom of the beaker. What is this and why is it produced?
Soot
produced by incomplete combustion
The demand for smaller hydrocarbon fraction high and supply is low, suggest 3 ways to how the oil industry could overcome this problem
- cracking
- use different/lighter crude oils
- development new techniques to use low demand fractions (or hydrocarbons depending on question) as fuels
What does volatile mean?
Evaporates easily/quickly
