C3.3 Crude oil Flashcards
(36 cards)
What is crude oil?
A mixture of hydrocarbons that can be separated by fractional distillation
What is a hydrocarbon?
A compound consisting of only carbon and hydrogen
Name 2 groups of hydrocarbons
- Alkanes
- Alkenes
Formula for alkanes
Cn H2n+2
Name first 4 alkanes
- methane CH4
- ethane C2H6
- propane C3H8
- butane C4H10
Properties of alkanes
- All alkanes contain strong covalent bonds between carbon and hydrogen atoms
- They are the only saturated hydrocarbons
AS THE CARBON CHAIN INCREASES: .BP and MP increases .viscosity(thickness) increases .less volatile .less flammable
Explanation on BP and MP on alkanes
As the carbon chain increases it means that there are more hydrogen and carbon atoms so there are stronger intermolecular forces so more energy is needed to break those bonds/forces
Explain fractional distillation of crude oil
- Crude oil is heated until most of it has evaporated and turned into a gas
- The evaporated crude oil enters the fractionating column
- The column is heated from the bottom so there is a temperature gradient (hottest at the bottom,coolest at the top)
- Long chain hydrocarbons have high BPs so they condense at the bottom and short hydrocarbons have low MPs so they condense at the top
- When the hydrocarbons reach a height in the column where the temperature is equal to its boiling point, it condenses to form a liquid
What is empirical formula?
The simplified whole number ratio of the number of atoms in a chemical formula of a compound
properties of covalent compounds
- low MP and BPs
- Cannot conduct electricity
- weaker intermolecular forces of attraction between atoms
- Atoms share electrons rather than transfer them
Advantages of molecular formula
- Tells you how many atoms of each element
- Used in equations
Disadvantages of molecular formula
- Doesn’t tell you the size of the atom
- Doesn’t tell you the structure or shape of the atom
Advantages of empirical formula
-Tells you the ratio of atoms in a formula as a whole number
Disadvantages of empirical formula
-Doesn’t always tell you the exact ratio as it may be rounded
Advantages of structural formula
- Shows arrangement of bonds in 2D
- Tells you how many electrons are transferred and how many bonds there are
Disadvantages of structural formula
- Doesn’t show the atoms size
- Doesn’t show the bond angles
- Not useful for equations
Advantages of ball and stick model
- Shows shape of the molecule in 3D
- Show bond angles
Disadvantages of ball and stick model
- Doesn’t show the actual atoms size
- Sizes of the atoms are not 100% accurate
What is cracking?
When a large hydrocarbon molecule is heated in the presence of a catalyst to break it down into smaller hydrocarbons
Why is cracking used?
Cracking is used because shorter chain hydrocarbons are in higher demand than long chain ones so in order to meet the demand cracking is used
What is thermal cracking?
A form of cracking using high temperature and pressure
What is catalytic cracking?
A form of cracking which uses low temperature and pressure to crack the hydrocarbons
- It is cheaper
- Used in industries
What is formed as a result of cracking?
Long chain alkane ——-> shorter chain alkane + alkene
Why do oil companies use cracking?
- Meet demand
- Produces more fuel
- Produces alkenes which can be used as plastic or feedstock for other compounds
