Paper 1 - Crude Oil and Alkanes Flashcards
What is a hydrocarbon?
Hydrocarbons are molecules that are formed of hydrogen and carbon atoms only
What is the general formula for alkanes?
CnH2n+2
What are the first 6 alkanes?
Methane
Ethane
Propane
Butane
Pentane
Hexane
What happens when fuel is burned?
Heat energy is released
How do SO2 and N02 contribute to acid rain?
- SO2/N02 react with H2O in clouds and form sulphuric/nitric acid
- this acid (acid rain), falls upon towns, corroding, buildings, and statues and killing plants by firming the soil
How does industrial process of fractional distillation, separate crude oil into fractions?
- crude oil is heated to 350°C to vaporise it.
- Gases and fractionates in column at the bottom.
- The gradient is exists: the tower is cooler at the top and hotter at the bottom.
4 vapours condensed back into liquids at their boiling points, different fractions have different boiling points, and collect at different levels of the tower - Small chain hydrocarbons have low boiling points and collect as gas at the top of the column where temperature is lower.
- Long chain hydrocarbons have high boarding points and collecting near the bottom of the tower where temperature is higher 
What is the impact of carbon monoxide?
- It is poisonous
- It replaces the oxygen in the blood with carbon
- Cells cannot aerobically respire
- Leads to: fainting, comas or death
What is the homologous series?
“Family” of hydrocarbons that all have similar chemical properties
How is crude oil formed and what of?
- microscopic plants, animals (plankton) that die and fall to the seabed
- Layers of sand and mud from on top
- Pressure and high temperatures cause oil to form
- Oil is obtained by drilling into seabed
Why are alkanes classified as saturated hydrocarbons?
- Alkanes do not have a double bond
- Alkanes have the maximum possible number of hydrogen atoms
What is the reaction between alkanes and halogens in the presence of UV radiation?
- This is known as a substitution reaction
- A halogen reacts with an alkane to form a haloalkane
- One hydrogen atom is replaced with a halogen atom
What does crude oil contain?
A mix of hydrocarbons
How is burning of hydrocarbons classified as a combustion reaction and what can it be used for?
- A reaction that burns a substance, releasing heat energy
- Useful for electricity, heating and transport
- Hydrocarbon + O2 —> CO2 + H2O
Draw the molecular structure of pentane
Draw it then google it
How are hydrocarbons represented?
- empirical formula (simplest)
- Molecular formula (actual molecular structure)
- Structural formula
- Displayed formula
How do you test for CO2?
- Below CO2 into clear lime water
- If limewater turns, cloudy, CO2 is present
What is an isomer?
Molecule with the same molecular formula as another molecule, but with a different displayed formula
What are the main uses for the fractions obtained from crude oil?
- Refinery gases - domestic heating
- Gasoline - fuel for petrol cars
- Kerosene - plane fuel
- Diesel oil - cars, lorries, vans
- (Heavy) fuel oil - ships
- Bitumen - repairing and laying tarmac
What are the properties of long chain hydrocarbons?
- High boiling point
- Low flammability
- High viscosity
What are the properties of short chain hydrocarbons?
- Low boiling point
- High flammability
- Low viscosity
What are the main fractions that are obtained from crude oil?
Coldest/Top:
- Refinery gases
- Gasoline (Petrol)
- Kerosene
- Diesel oil
- (Heavy) fuel oil
- Bitumen
Hottest/Bottom:
What is the trend in colour, boiling point and viscosity of the main fractions?
As the hydrocarbon chains become longer: the boiling point increases, viscosity increases and colour becomes darker
How do you test for alkenes and alkanes?
- Use bromine water (initially orange)
- Add hydrocarbon solution
- If solution turns, colourless, hydrocarbon is an alkene
- A solution remains orange, hydrocarbon is an alkane
What is a functional group?
Specific group of atoms or bonds within a molecule that is responsible for characteristics in chemical reactions
Give an example of isomers
Butane and cyclobutane
(both C4H8)
In car engines, what is the temperature high enough to do?
To allow nitrogen and oxygen from the air to react, forming oxides of nitrogen such as NO2 or NO
How was the reaction classified as a substitution reaction?
- Halogens react with alkanes to make haloalkanes
- UV light is needed
- One hydrogen atom is replaced by a halogen atom
- e.g. methane + bromine —> bromomethane + hydrogen bromide
How does the combustion of sulphur impurities and hydrocarbon fuels result in the formation of sulphur dioxide?
- Impure hydrocarbons are burned and sulphur is produced
- Sulphur impurities react with oxygen in the air, forming sulphur dioxide
What are the products of complete combustion?
Carbon dioxide and water
What are the products of incomplete combustion?
Carbon monoxide, soot and water
