alkanes , alkenes , carboxylic acids

• What is the general formula for alkanes?

  C$_n$H$_{2n+2}$
• Name the first four alkanes and their molecular formulae.

  Methane - CH4, Ethane - C2H6, Propane - C3H8, Butane - C4H10
• What type of bond is formed between carbon and hydrogen atoms in alkanes?

  Covalent bonds
• What is the displayed formula of ethane?

  C2H6

  
• Why are alkanes classified as saturated hydrocarbons?

  Because all C-C bonds are single bonds.
• What is the general formula for alkenes?

  CnH2n
• Name the first four alkenes and write their molecular formulae.

  • Ethene - C2H4
  • Propene - C3H6
  • Butene - C4H8
  • Pentene - C5H10
• Why are alkenes classified as unsaturated hydrocarbons?

  Because they contain double carbon bonds, C=C.
• What is a functional group?

  The group of atoms responsible for the main chemical properties of a compound.
• What functional group do alkenes contain?

  C=C double bond.
• What is the difference between but-1-ene and but-2-ene?

  But-1-ene has a double bond between the first and second carbon, while but-2-ene has it between the second and third carbon.
• What is the word and balanced symbol equation for the addition reaction between ethene and bromine?

  Ethene + Bromine → 1,2-dibromoethane; C2H4 + Br2 → C2H2Br2
• How can bromine water be used to distinguish between alkanes and alkenes?

  Alkanes keep the solution orange, while alkenes turn it colorless.
• Why do alkenes decolourise bromine water?

  Because the double bond allows alkenes to react with bromine to form a bromoalkane.
• What is produced when a hydrocarbon is completely combusted?

  Water and carbon dioxide are produced.
• What happens to the carbon and hydrogen during complete combustion of a hydrocarbon?

  Carbon and hydrogen are oxidised.
• Write a balanced symbol equation for the complete combustion of propane.

  C3H8 + 5O2 → 3CO2 + 4H2O
• What type of reaction occurs when hydrocarbons undergo complete combustion?

  An exothermic reaction.
• What functional group do alcohols contain?

  • OH
• What are the names and formulae of the first four alcohols?

  • Methanol (CH3OH)
  • Ethanol (C2H5OH)
  • Propanol (C3H7OH)
  • Butanol (C4H9OH)
• How does the boiling point of alcohols change with chain length?

  As the chain length of an alcohol increases, boiling point increases.
• How can an alkene be produced from an alcohol?

  During a dehydration reaction with sulfuric acid, water is also produced.
• What functional group do carboxylic acids contain?

  • COOH
• What are the names and formulae of the first four carboxylic acids?

  • Methanoic acid (HCOOH)
  • Ethanoic acid (CH3COOH)
  • Propanoic acid (C2H5COOH)
  • Butanoic acid (C3H7COOH)
• What are the typical properties of solutions of carboxylic acids?

  Acidic
• How can ethanol be converted into ethanoic acid?

  Through oxidation.
• What is the product when butanol is oxidised?

  Butanoic acid
• Why do members of the same homologous series undergo similar reactions?

  The molecules have the same functional group so have similar chemical properties.
• Which renewable process can be used to produce ethanol?

  By fermentation of carbohydrates in aqueous solution with yeast.
• What conditions are required for the fermentation of glucose to form ethanol?

  • Anaerobic conditions (no oxygen).
  • Warm temperature to increase the rate of reaction without denaturing enzymes in the yeast.
• What is the word and balanced chemical equation for the fermentation of glucose?

  • Word equation: Glucose → ethanol + carbon dioxide
  • Balanced equation: C6H12O6 → 2C2H5OH + 2CO2
• How can pure concentrated ethanol be extracted from the fermentation mixture?

  By fractional distillation.
• what is the general formula for alcohols


  Cn H2n+1 oh
• general formula for carboxylic acids


  cn 2n+1 where n is the number of carbon atoms minus 1
• What are properties of alcohol 


  Combust completely

  Good solvent

  Can be oxidised to form carboxylic acids
• Properties of carboxylic acids 


  Weak acids , follow same rules as other acuds
• What forms when alcohol is burned

  Water and carbon dioxide