chemistry c3 WJEC

note cards on Alkanes and alkenes, Enzymes, Ethanol+ alcohol and ethanoic acid for WJEC

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  • Created by: Iwan
  • Created on: 04-05-09 20:58

carbon compounds


  • Alkanes are saterated hydrocarbons.
  • Each carbon atom is bonded to 4 other atoms
  • general formula for any alkane = CnH2n+n
  • Alkanes with the same formula but different structures are called isomers


  • all their names end in -ene
  • they all contain a C=C double bond
  • General formula= CnH2n
  • Alkenes are extreamly reactive because the double bond can break open to allow other atoms to add on
  • When an alkene is added to bromine water it turns colourless
  • the double bond splits open and the bromine adds on, this is called an addition reaction
  • the product is saturated
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  • Enzymes are biological catalysts
  • Each enzyme has an optimum temperature and and optimum pH at which it works best at
  • above the optimum temperature the activity begins to fall because the ebzyme is denatured
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Ethanol and alcohols

  • Ethanol is made from sugars by fermentation
  • enzymes in yeast change the sugar to ethanol and carbon-dioxide
  • glucose = ethanol + carbondioxide
  • C6H12O6 = 2C2H5OH + 2CO2
  • ethanol can be obtained from the reaction mixture by distillation or fractional distillation
  • Ethanol is used in alcholic drinks as a solvent and as a fuel
  • Ethanol produces about 70% as much energy as petrol but it requires a large amount of sunlight and lots of land

Importance of ethanol

  • small amounts of ethanol are thought to help against heart disease
  • excessive alcohol intake may lead to liver damage or alcohol dependency
  • increased cost to the NHS due to alcohol related incidents
  • drink driving
  • impact on families
  • taxes on alcoholic drinks raise money for public spending

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Ethanol and Ethanoic acid

  • Ethanol when exposed to the air undergoes oxydation caused by microbes
  • the microbes change the ethanol into ethanoic acid
  • ethanoic caid is a member of the carboxylic acid family
  • Ethanoic caid reacts with sodium carbonate to give off carbon dioxide gas. fizzing is seen
  • this reaction can be used as a test for carboxylic acid
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