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
What is the general formula for alkenes?
CnH2n
Are alkenes reactive?
They are reactive as they have a double carbon bond which is less difficult to break
Which is the smallest alkane?
Methane
Which is the smallest alkene?
Ethene
What is the name of the alkane with the formula C2H4
Ethene
What is the name of the alkane with the formula C3H6
Propene
What is the name of the alkane with the formula C4H8
Butene
What is the name of the alkane with the formula C5H10
Pentene
What suffix do all alkenes have?
-ene
What is the general equation for complete combustion?
Fuel + Oxygen -> Carbon Dioxide + Water
What is the general equation for incomplete combustion?
Fuel + Oxygen -> Carbon Monoxide + Water + Carbon
What is the difference between complete and incomplete combustion?
Complete combustion happens in an oxygen where the entire molecule is broken down and
Incomplete combustion happens when there isn’t enough oxygen where some of the molecule is broken down
What type of reaction is combustion?
Oxidation
Exothermic
What colour is the flame in complete combustion?
Blue
What colour is the flame in incomplete combustion?
Yellow
Which type of combustion releases more energy?
Complete Combustion
What other by product do we see during an incomplete reaction?
Black soot forms (carbon)
What tests do we do for the products of combustion?
Put a flame under a funnel which leads into a U-bend (in an ice bowl with cobalt chloride or anhydrous copper sulphate paper) and the pipe continues into a test tube with limewater in it
How do we test for Carbon Dioxide?
Limewater turns cloudy and bubbles
What are the two ways of testing for water?
Cobalt Chloride Paper
Anhydrous Copper Sulphate Paper
Both go from blue to pink in the presence of water
Define Cracking
Cracking is the breaking down of less useful, large hydrocarbon molecules into smaller, more useful hydrocarbon molecules
Which hydrocarbons do we crack?
Alkanes
What are alkanes cracked into?
It is always random but you always get:
Alkenes
And Alkane
What are the three ways of cracking?
Catalytic
Steam
Thermal
Describe catalytic cracking
High temperatures (500°) Zeolite Catalysts
Describe steam cracking
High temperature
Steam
Describe thermal cracking
High temperature (700°) 70 atms pressure
Which is the most common form of cracking?
Catalytic
Describe the Addition reactions of alkenes
Another molecule (with two atoms) bonds to the alkene double bond. These atoms make bonds with the carbon atoms and the double bond becomes a single.
Describe Halogenation of alkenes
When you react halogens with alkenes
Halogens are diatomic
The diatomic atoms bond individually to the carbon atoms and the double bond becomes single.
Describe the test for alkenes
Halogenation of alkenes
In this process the halogen is decolourised
What is the product of halegenation?
Di - (halogen) - (alkene) i.e.: dibromoethane dichloroethane diiodoethane (these are the reactions with ethane)
Describe Hydrogenation of Alkanes
Alkene reacts with Hydrogen (H2) to form an alkane
What factors are needed hydrogenation?
150*C heat
Nickel Catalyst
Describe the reaction with alkanes and water
This is reversible
The alkane becomes a molecule with only a single carbon bond
One if the hydrogen atoms bonds to a carbon and the OH molecule also bonds to a carbon atom
What is the product of the reaction with alkanes and water?
Alchol
What is a functional group?
A group of atoms whose bonding is the same from molecule to molecule.
What are alchols?
A homologous series with the functional group -OH
Describe an alcohol molecule
The carbon atoms are all bonded to hydrogen atoms except for one which bonds to an oxygen and the hydrogen atom
What is the general formula for an alcohol?
CnH2n+1OH
What is the name of the alcohol with the formula CH3OH
Methanol
What is the name of the alcohol with the formula C2H5OH
Ethanol
What is the name of the alcohol with the formula C3H7OH
Propanol
What is the name of the alcohol with the formula C4H9OH
Butanol
What is the name of the alcohol with the formula C5H11OH
Pentanol
Define Chemical Feedstock
Used to make other chemicals such as adhesives, foams, and solvents
What is Methanol used for?
Chemical feedstock
What is Ethanol used for?
Cosmetics
Alcoholic Drinks
Describe the boiling points of alcohols
Short length have low boiling points
Describe the solubility of alcohols
Generally soluble but longer chain lengths are less soluble
What are the two ways of making alcohols?
Fermentation
Catalytic
Describe Fermentation to create alcohols
Glucose -> Ethanol + Carbon Dioxide
Describe the process of using a catalyst to create alcohols
Alkene + Water ⇌ Alcohol
What is the conditions are used to create alcohols (catalytic)?
Phosphoric Acid (H3Po2) High Pressure Steam
How does alcohol react with sodium?
(Less vigorously than sodium with water)
Sinks and fizzes, making a pop sound
Becomes and acidic solution
Write the equation for propanol burning
2C3H7OH + 9O2 -> 6CO2 + 8H2O
Write the equation for sodium reacting with water
3Na + 3H2O -> 3NaOH +H2
Write the equation for sodium reacting with methanol
2Na + 2CH3OH -> 2CH3ONa + H2
What functional group is propanol in?
-OH group
