Flashcards in Organic Chemistry Deck (111)
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
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
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