Organic Chemistry Flashcards
What is crude oil
A mixture of hydrocarbons with a range of boiling points
How is crude oil formed
Crude oil was formed millions of years ago from the remains of dead sea creatures that fell to the seabed.
These remains were covered by mud and bacteria and then decayed slowly in the oxygen-free environment.
The deposits became buried under more sediments, and the underground pressure together with heat slowly converted organic matter into crude oil and natural gas.
What is fractional distillation
The use of distillation to separate a mixture of miscible liquids, making use of different boiling points
How does fractional distillation work
The fractioning column has a large surface area.
Evaporation followed by condensation of the vapour takes place many times on the surface of the fractioning column.
Only the vapour with the lowest boiling point reaches the top of the column and condenses to be collected as a liquid.
This continues until the fraction with the highest boiling point condenses.
What happens in the industrial process of fractional distillation
It occurs in a tall tower which is hottest at the bottom and gradually cools towards the top. The process is continuous.
This process pipes off the different fractions at different points in the same column.
Give the order of the fractions that come out of crude oil
Refinery gases Gasoline Kerosene Diesel oil Fuel oil Bitumen
Source for experiment, approx BP, number of carbons and use as fuel of refinery gases
Butane lighter, around 40 degrees, 1-4 carbons, domestic heating and cooking
Source for experiment, number of carbons and use as fuel of gasoline
Light petroleum, 4-12 carbons, petrol for motor vehicles
Source for experiment, number of carbons and use as fuel of kerosene
Paraffin, 9-16 carbons, jet aircraft fuel
Source for experiment, number of carbons and use as fuel of diesel oil
Petroleum, 15-25 carbons, diesel fuel for cars and lorries
Source for experiment, number of carbons and use as fuel of fuel oil
Central heating oil, 20-70 carbons, oil powered central heating systems
Source for experiment, approx BP, number of carbons and use as fuel of bitumen
Bitumen paint, around 400 degrees, more than 70 carbons, road making
What happens to the BP, volatility and viscosity as the number of carbon atoms in the molecule increases
BP increases
Liquids become less volatile
Liquids become for viscous
Burn less easily
Why does BP increase as the number of carbon atoms in the molecule increases
Because there are larger intermolecular attractions between larger molecules so more energy is needed to separate the hydrocarbon molecules.
Why do liquids become less volatile as the number of carbon atoms in the molecule increases
Larger molecules evaporate more slowly because there are stronger intermolecular attractions
Why do liquids become more viscous as the number of carbon atoms in the molecule increases
Because of greater intermolecular attractions
What are the dangers of incomplete combustion
If a hydrocarbon is is burnt in a limited supply of oxygen, carbon monoxide is formed. This is toxic to humans because it reduces the capacity of the blood to carry oxygen.
What is photochemical smog and the dangers
In a car engine, the temperature is high enough that nitrogen and oxygen rom the air react to form nitrogen oxides. These react in the air with hydrocarbons to form photochemical smog. This can lead to poor air quality and respiratory diseases
What is acid rain and the dangers
If sulphur is present in fuels, sulphur dioxide may form when they are burnt.
This dissolves in water droplets in the atmosphere to form sulphuric acid.
This can cause damage to plants, animals and limestone buildings. Nitrogen oxides dissolve in water to form acid rain too
What are hydrocarbons
Molecules made up of hydrogen and carbon atoms only
What does organic mean
A compound containing at least one carbon-hydrogen bond
What is a homologous series
A family of compounds with similar properties due to their similar bonding. They have the same general formula
What does saturated mean
A compound consisting of single bonds ONLY
What does unsaturated mean
A compound containing a carbon-carbon double bond
What is the definition of “general formula”
A formula that describes a homologous series from which you can derive the molecular formula
What is the definition of the “molecular formula”
Formula that describes the number of each type of atom in a molecule
What is the definition of the “empirical formula”
The simplest whole number ratio of atoms
What are (structural) isomers
Molecules with the same molecular formula but different structural formula
What are isotopes
Atoms of an element with a different number of neutrons
What is an allotrope
Forms of an element that exist in the same state but have different properties because the atoms are arranged differently
What is the structural formula
Eg: butane CH3CH2CH2CH3
What is the displayed formula
When you draw it out
What are alkanes
Saturated hydrocarbons
What is the general formula for alkanes
CnH2n+2
What are the products of complete combustion with alkanes
Alkane + oxygen = carbon dioxide + water
Eg: CH4 + 202 = CO2 + 2H2O
Why does incomplete combustion occur
When there is not enough oxygen
What can the products of incomplete combustion be
CO + H2O
CO + C + H2O
C + H20
(C + CO + CO2 + H2O)?
Describe the halogenation of alkanes
Alkanes will react with a halogen with UV light present as an initiator of the reaction. It is a photochemical reaction.
A hydrogen atom in the alkane is replaced with a bromine atom - this is known as a substitution reaction.
What is the equation for the halogenation of methane with bromine
Methane + bromine = bromomethane + hydrogen bromide
CH4 + Br2 = UV = CBrH3 + HBr
What are alkenes
Unsaturated hydrocarbons
What is the general formula for alkenes
CnH2n
Why can’t methene exist
Because there is only one carbon and the carbon cannot have a double bond with a hydrogen
Why does cracking take place
Because the demand for petrol is greater than the amount of gasoline fraction obtained from fractional distillation
Describe the process of cracking
Large, saturated hydrocarbons can be broken down into smaller hydrocarbons by a thermal decomposition reaction known as cracking. The reaction also produces small alkenes.
The reaction requires vigorous heating and an aluminium oxide catalyst.