Organic Chemistry Flashcards
What type of resource is crude oil?
Finite (will run out quicker, then we can replace it.)
Where is crude oil found
In rocks/the bottom of the Sea
How was crude oil formed?
Remains of plankton/biomass buried in mud over millions of years
What is crude oil?
A mixture of hydrocarbons
What is a hydrocarbon?
A substance made up of hydrogen and carbon elements only
What type of hydrocarbons are found in crude oil?
Alkanes
what is the general formula of an alkane?
C(n)H(2n+2)
What is a homologous series?
A series of organic compounds that have the same general formula
E.g., the general formula of alkanes is C(n)H(2n+2)
What are the first for alkanes?
Methane, ethane, propane, butane
How can alkanes be presented?
Molecular formula (shows the number of atoms of each element)
E.g. C2H6
Displayed formula (shows the bonds between atoms)
How is crude oil separated into its fractions?
Fractional distillation
What two processes are involved in fractional distillation?
Evaporation and condensation
What is fraction?
Each fraction consist of groups of hydrocarbons of similar chain lengths
What are fractions used to produce?
Fuels on feedstock for the petrochemical industry
Name some fractions produced from crude oil
Petrol
Diesel oil
Kerosene
Heavy fuel oil
Liquefied petroleum gases
What products are produced from the petrochemical industry?
Solvent
Lubricants
Polymers
Detergent
How is crude oil separated?
- Crude oil is heated up to become a vapour.
- It enters the bottom of the fractionating column where it is the hottest at the bottom and cools as you get higher up (temperature gradient.)
- As the vapours rise, they condense when they reach their boiling points
- So different fractions are collected at different levels in a continuous process.
- Hydrocarbons with the smallest molecules have the lowest boiling point and are collected at the top.
- Large molecules with higher boiling point are collected near the bottom.
Where are the largest molecules found?
The bottom of the fractionating column
Where are the smallest molecules found?
At the top of the fractionating column
What are the trends in the properties of alkanes?
As molecular size increases:
Boiling point increases
Viscosity increases (thickness)
Flammability (how easily they are set on fire) decrease
Why do large molecules have the highest boiling points?
There are more intermolecular forces between molecules therefore more energy is required to overcome these
What is released during the a combustion of hydrocarbon?
Energy
What are the two types of combustion?
Complete and incomplete
Describe the difference between the two types of combustions
Complete combustion = large supply of oxygen
Incomplete combustion = limited supply of oxygen
What happens to the carbon and hydrogen when a hydrocarbon is burnt
They are oxidised (they both gain oxygen to become CO2 and H2O)
What is produced during complete combustion of a hydrocarbon fuel?
Carbon dioxide and water
Write a word equation for the complete combustion of propane
Propane + oxygen —> carbon dioxide + water
Write a balanced symbol equation for the combustion of propane (tip, always balance to C then the H.)
C3H8 + 5O2 —> 3CO2 + 4H2O
How are hydrocarbons broken down into smaller more useful molecules?
Cracking
Why are hydrocarbons cracked?
To meet demands for high demand products such as fuels
What are the two methods of cracking?
Catalytic and steam
What are the conditions for catalytic cracking
High temperature of 550°C
Zeolite catalyst (is made up from aluminium oxide and silicon oxide)
What are the conditions for steam cracking?
Higher temperature then catalytic cracking
water vapour/steam
What are the products formed from cracking
Long alkane —> Shorter alkane+ alkene