Organic Chemistry (C7) Flashcards
What is crude oil?
A thick mixture extracted from the earth (where sea is or was)
It is made of a mixture of hydrocarbons
How does crude oil form?
When sea ceatures (specifically plankton) die and fall to the sea bed they tend to become covered by other layers of sediment.
Over time, pressure and heat may mean they do not rot but instead release the carbon in their bodies.
Over millions of years this creates crude oil.
What are the utilities of crude oil?
None it needs to be refined
What does it mean to refine crude oil?
Seperate it into useful hydrocarbons
What is the difference between different hydrocarbons in crude oil?
They have different molecular chain lengths (they are different sizes). This means they have different properties.
How is crude oil refined?
Fractional distillation
What equipment is used for large-scale fractional distillation?
Fractional Column
Farctional Tower
Roughly what heat is the bottom of a fractional column?
330°C - 350°C
Put simply, what happens in a fractional column?
The hydrocarbons vaporise and rise
The column is progressively cooler, higher up the column and thus (depending on boiling point) some of the hydrocarbons will condense again at specific heights.
Here they can be collected.
What organism is most crude oil formed from the fossils of?
Plankton
How deep is crude oil usually found?
1 or 2 miles
Why do different molecules have different properties?
They are different lengths, some chains are longer than others
Answer the 6 marker:
Explain Fractional Distillation
(example answer on back)
Actually write it
Fractional distillation is a process by which different hydrocarbons are seperated from crude oil. This process is known as refining and is done because the mixture is not useful but the individual carbons are greatly so.
Different hydrocarbons have different chain lengths, the longer they are the more intermolecular forces and thus the more energy in needed to seperate them. This means the larger molecules have higher boiling points than the small ones.
During fractional distillation the bottom of a fractional column is heated to approx. 350°C and all tht crude oil vaporises. Higher up the column it is cooler and thus some fractions begin to condense. These are each collected as liquids at varying heights. Only the smalest molecules leave as a gas due to their low boiling point.
What do the properties of hydrocarbon depend on?
Chain length
Define Volatility
The tendancy to become a gas
Define Viscocity
Thickness
Which have higher boiling points?
Short or long chain hydrocarbons
Long chain hydrocarbons
Why do long chain hydrocarbons have a higher boiling point?
They have more intermolecular forces that need to be broken
Which have higher volatility?
Short or long chain hydrocarbons
Short chain hydrocarbons
Why do short chain hydrocarbons have a higher volatility?
They have fewer intermolecular forces and so they can easily be broken
Which have higher viscocity?
Short or long chain hydrocarbons
Long chain hydrocarbons
Why do long chain hydrocarbons have a higher viscocity?
They have more atoms in each molecules so they can not flow easily over each other
Which have higher flamability?
Short or long chain hydrocarbons
Short chain hydrocarbons
Why do short chain hydrocarbons have a higher flamibility?
Less energy is needed
Why do long chain hydrocarbons cause sooty fires?
if they can be burned
A lot of energy is needed and therefore combustion is not usually complete
(Some are not flamable because of this)
What are the method to explore the viscocity of a hydrocarbon?
Time to Drain
Air Bublle
What happens in a ‘Time to drain’ practical?
A syringe is filled with the hydrocarbon
This is held over a beaker
The plunger is pulled out and simultaneously a timer is begun
When all the liquid has pured out it is stopped
Repeat twice more for accuracy
More viscous liquids take longer to clear
What are alkanes?
Alkanes are a family of saturated hydrocarbon compounds
What suffix do alkanes have?
-ane
What is the general formula of an alkane?
CnH2n+2
What are the bonds in alkanes?
Alkanes are made up of single covalent bonds between hydrogen and carbon atoms
What is the name of the alkane with the formula CH4
Methane
What is the name of the alkane with the formula C4H10
Butane
What is the name of the alkane with the formula C2H6
Ethane
What is the name of the alkane with the formula C3H8
Propane
What is the name of the alkane with the formula C5H12
Pentane
Describe the reactivity of alkanes
Non reactive as all the outer shells are full (except for combustion)
It is a saturated molecule.
Define a saturated molecule
Containing the greatest possible number of hydrogen atoms, without carbon=carbon double or triple bonds
Define Alkenes
Unsaturated hydrocarbons
They contain at least 1 double carbon covalent bond C=C