AQA Chemistry As : Unit 1 – Organic chemistry

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Molecular formula
The actual number of atoms of each element in a molecule
Structural formula
Shows the atoms carbon by carbon and the attached hydrogens and functional groups
Displayed formula
Shows how all the atoms are arranged and all the bonds between them
Empirical formula
The simplest whole number ration of each element in a compound
Homologous series
Is a group of organic compounds that have the same general formula and similar chemical properties
General formulas
Alkane – CnH2n+2
Alkene – CnH2n
Nitrogen oxides – NOx
contain double bond
Structural Isomers
Have same molecular formula but different structural formula

1. Chain Isomer – different arrangements of carbon skeleton
2. Position Isomer – same carbon skeleton but functional group on a different carbon
3. Functional group isomer – same atoms arranged into different functional group

Molecule that contains only hydrogen and carbon atoms
Crude oil
Is a mixture of alkanes
Fractional distillation
used to separate crude oil

1. Crude oil is vaporized @ 350 + rises up fractionating column
2. Largest hydrocarbons don’t vaporise bc boiling point too high, run to bottom as liquid
3. Gets cooler as you go up fractionating column forming temperature gradient
4. Boiling points of alkanes increase as they get bigger so each fraction condenses at different temp, drawn off at different levels
5. Hydrocarbons with lowest boiling points drawn off as gases

Cracking is breaking long chain alkanes into smaller chain hydrocarbons, involves breaking the c-c bonds

Done bc smaller chain alkenes are in higher demand

*Thermal Cracking*
– high temp (1000c) + high pressure (70atm)
– produces lots of alkenes used to make polymers (e.g polyethene)

*Catalytic Cracking*
– High temp (450c) + slight pressur
– Produces aromation hydrocarbons + motor fuels
– Uses zeolite catalyst

*Complete combustion*
-when you burn a substance in a plentiful supply of oxygen, produces carbon dioxide + water

*Incomplete Combustion*
-when you burn a substance where there is a lack of oxygen producing carbon, carbon monoxide + carbon dioxide

Nitrogen oxides are poisonous + toxic molecules
Formed when oxygen and nitrogen in the air are forced to react in vehicle engines bc of high temp + pressure

3 main pollutants for exhausts:
– unburnt hydrocarbons
-nitrogen oxides
– carbon monoxide

Catalytic converters remove these, use catalyst such as platinum to convert into less harmful chemicals

Sulfur dioxide
Acid rain caused when fossil fuels containing sulfur or nitrogen are burnt to produce sulfur dioxide or nitrogen oxide which enters atmosphere and dissolves in moisture

This converts it to sulfuric acid/ nitric acid, destroying trees, vegetation, killing fish bc ph of water + eroding limestone architecture

*Flue gas desulfurisation*
Sulfur dioxide can be removed from power station flue gases using calcium oxide in neutralisation reaction

Global Warming
Greenhouse Effect
– electromagnetic radiation from sun reaches earth + is absorbed
– Earth re-emits as infrared radiation, gases absorb this and re emit back to earth

3 main geenhouse gases:
– water vapour
– carbon dioxide
– methane

Categories: Organic Chemistry