Higher Chemistry UNIT 2

Higher Chemistry Unit 2


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What is petrol?

  • product of crude oil
  • crude oil is fractionally distilled to separate fractions
  • petrol is made by reforming the naptha fraction
  • blend of hydrocarbons containing between 5 and 10 carbon atoms in their chains
  • blend depends on temperature
  • in summer, petrol contains fewer volatile hydrocarbons
  • in winter, petrol contains more volatile hydrocarbons
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Petrol engine

  • intake
  • compression
  • combustion
  • exhaust
  • when burnt, petrol produces waste gases
  • under certain conditions the fuel can auto ignite- called knocking
  • knocking reduces engine performance
  • octane number of a fuel is its ability to resist knocking
  • three ways to increase burning efficiency of petrol-
  • 1- use alkanes with higher degree of branching
  • 2- use aromatic hydro carbons
  • 3- use cycloalkanes
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  • reforming alters the arrangement of atoms in molecules without necessarily changing the number of carbon atoms per molecule
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Advantages of alternative fuels

  •  reduce harmful exhaust emissions
  • they do not use up a finite resource- naptha- which is obtained from crude oil
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biofuels are fuels which come from plant or animal matter


  • is made from sugar cane and is fermented to produce ethanol
  • is renewable
  • burns efficently and produces less carbon monoxide than petrol


  • mainly made up of 50-80% methane. Rest is carbon dioxide
  • made form fermentation of plant and animal matter inder anaerobic conditions Bacteria act on waste materials to form biogas
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its main synthesis route is by passing synthesis gas over a heated catalyst


  • burns completely- producing less soot and carbon monoxide
  • less volatile than petrol


  • produces half the energy of petrol
  • toxic
  • methanol absorbs water
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  • can be produced by electrolysis of water
  • or produced when hydrocarbons react with steam
  • reduces build up of carbon dioxide in the air


  • hydrogen storage- is heavy in liquid or compressed form
  • liquefying hydrogen is expensive
  • extremely flammable
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  • Cn H2n + 2
  • carbon to carbon single bonds
  • name must end in -ane
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  • CnH2n
  • functional group is the C=C
  • name must end in -ene
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  • CnH2n-2
  • functional group is the carbon to carbon triple bond
  • name must end in -yne
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  • contains a hydroxyl functional group -OH
  • names end in -ol

Primary Alcohol- wil have the -OH group at the end of the molecule

Secondary Alcohol- will have the -OH group in the middle of the molecule

Tertiary Alcohol- will have the -OH group in the middle of the molecule directly opposite a branch

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Aldehydes and Ketones

they contain the carbonyl functional group C=O


  • also known as alkanals
  • name will end in -al
  • carbonyl always found at the end of the molecule


  • are also known as alkanones
  • names end in -one
  • carbonyl group will be found in the middle of the molecule
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Carboxylic acids

  • also known as alkanoic acids
  • names end in -oic acid
  • have  carboxyl functional group ( COOH)
  • carboxyl group at the end of the chain
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  • can be identified by their ester link
  • are formed by the condensation reaction between an alkanoic acid and alcohol
  • all ester's end in -oate
  • first part of name comes from the alcohol, second part comes from the alkanoic acid.
  • esters can be broken down in a hydrolysis reaction
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Aromatic hydrocarbons

  • simplest aromatic hydrocarbon is benzene
  • has formula C6H6 and has a cyclic structural formula
  • each carbon atom has 4 outer electrons. 1 is spare from each carbon atom and these form an electron cloud. They are delocalised.
  • These delocalised electrons make the ring very stable.
  • a benzene ring where one of the hydrogen atoms has been substituted by another group is known as the phenyl group ( C6H5)
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most complete form of oxidation is combustion

oxidation results in an increase in the oxygen to hydrogen ratio

Primary alcohols- are oxidised first to aldehydes and then to carboxylic acids

Secondary alcohols- are oxidised to ketones

Tertiary alcohols- can't be oxidised

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Aldehydes and ketones can be returned back to their corresponding alcohols using the reducing agent, lithium aluminium hydride.

Reduction results in an increase in the oxygen to hydrogen ratio

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Hey Catriona,
These Revision cards are great! Ive been trying to find something like this for ages. Thanks, Molly x


you can brake ma hart but u cant braek my swag

Nice notes they were very useful


u mispellet "Under" inder biogas


I wud nt sho this 2ma pewpils

Jordan Ball

thanks this is really helpful

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