Organic chemistry Flashcards
What is crude oil?
-Crude oil is found in rocks.
-It is a FINITE RESOURCE (meaning one day it will run out)
-Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
What is crude oil a mixture of?
Crude oil is a mixture of molecules called hydrocarbons.
What are hydrocarbons?
Hydrocarbons are molecules made up of hydrogen and carbon atoms.
What are ALKANES?
SATURATED molecules because the carbon atoms fully bonded to hydrogen atoms.
What are the 2 key features of ALKANES?
-They have the general formula : CnH2n+2
-Alkanes only have single covalent bonds between the carbon atoms.
What is the formula for alkanes?
CnH2n+2
number of carbon atoms x 2 and then + 2 = number of hydrogen atoms
What are the structures for METHANE, ETHANE, PROPANE AND BUTANE?
Methane = CH4 (1 carbon and 4 hydrogen)
Ethane = C2H6 (2 carbon and 6 hydrogen)
Propane = C3H8 (3 carbon and 8 hydrogen)
Butane = C4H10 (4 carbon and 10 hydrogen)
What are the 3 key properties of hydrocarbons?
-boiling points
-viscosity
-flammability
What is the definition of viscosity?
Viscosity tells us the thickness of a fluid.
Fluids with a high viscosity flow slowly. {Good example is : honey}
What happens to the molecules as the size of the hydrocarbons molecules increases : in terms of viscosity?
As the size of the hydrocarbon molecules increases, the molecules get more viscous.
Very long chains of hydrocarbon flow very slowly indeed. In other words long chain hydrocarbons are extremely viscous..
What is the definition of flammability?
Flammability tells us how easily a hydrocarbons combusts (burns).
Short chain hydrocarbons are extremely flammable.
As the size of hydrocarbon molecules increases, the molecules become less flammable. Long chain molecules are very difficult to burn.
What happens to the molecules as the size of the hydrocarbons molecules increases : in terms of flammability?
As the size of hydrocarbon molecules increases, the molecules become less flammable. Long chain molecules are very difficult to burn.
What is the definition of boiling point?
The boiling point is the temperature at which a liquid turns to a gas.
All methane, ethane, propane and butane are all gases at room temperature. This is because they all have boiling points lower than room temperature.
What happens to the molecules as the size of the hydrocarbons molecules increases : in terms of boiling point?
As the size of the hydrocarbon molecules increases, the boiling point also increases.
What happens when hydrocarbons are combusted {burned} ?
The combustion of hydrocarbon fuels releases energy.
What are fractions?
Fractions contain hydrocarbons with a similar number of carbon atoms.
Some of these fractions can be used as fuel like petrol and diesel or heavy fuel oil.
Some fractions are used as a feedstock for the petrochemical industry.
What does the carbon and hydrogen atoms in the fuel react with during combustion?
During combustion, the carbon and hydrogen atoms react with oxygen. The carbon and hydrogen are oxidised.
What does feedstock mean?
A feedstock is a chemical used to make other chemicals.
Example are solvents or lubricants.
If the oxygen is unlimited during the combustion of carbon and hydrogen atoms, what is produced and what is this called?
produces carbon dioxide and water.
This is called complete combustion.
The complete combustion of a hydrocarbon produces carbon dioxide and water
What are the stages of Fractional Distillation of Crude Oil?
- Firstly, the crude oil is heated to a very high temperature. This causes the crude oil to boil. Meaning all the hydrocarbons begin to EVAPORATE and turn into a gas.
- The crude oil vapour is now fed into the fractional distillation column. The column is hotter at the bottom and cooler at the top.
- The hydrocarbon vapour now rise up the column. They begin to CONDENSE when they reach to boiling point. This removes the liquid fractions of the crude oil
- The remaining hydrocarbons move up the column continue moving up the column. They now CONDENSE when they reach their boiling points.
What is cracking?
In cracking, longer chain alkanes is broken down (cracked) to produce smaller, more useful molecules like this.
The 2 products are a shorter chain alkane and an alkene.
What are the conditions for cracking?
Catalytic cracking:
Temperature: ~ 550°C
Catalyst: Zeolite (aluminium oxide & silicon dioxide)
Steam cracking:
Temperature: Over 800°C
No catalyst, but steam is used
What is meant by an alkene?
Alkenes have a double covalent bond between the 2 carbon atoms.
What is the test for alkene?
Alkenes are more reactive them alkanes. We can use this as a test for alkenes.
1.We test for alkenes using bromine water which is ORANGE.
2. We shake our alkene with our bromine water then the bromine water turns colourless.
