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2016-01-16 19:30:07
AS Chemistry Unit 2
AS Chemistry Unit 2
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  1. What is the general formula for alcohols?
    • CnH2n+1OH
  2. What is the suffix to indicate alcohol is present in the name of a term?
  3. What is a primary alcohol?
    Primary alcohols are alcohols where 1 carbon is attached to the carbon adjoining the oxygen from the alcohol group
  4. What is a secondary alcohol
    Secondary alcohols are alcohols where 2 carbon are attached to the carbon adjoining the oxygen
  5. What is a tertiary alcohol?
    Tertiary alcohols are alcohols where 3 carbon are attached to the carbon adjoining the oxygen
  6. What the word equation for the reaction of alcohol with oxygen and symbol equation for the reaction of ethanol with water? ( 2 marks)
    Alcohol + oxygen → Carbon dioxide + Water

    CH3CH2OH (l) + 3O2(g) → 2CO2(g)+ 3H2O(l)
  7. What the balanced equation for the reaction between sodium and alcohol(ethanol) and what can it be used for and what are the products? (3 marks)
    2CH3CH2OH (l) + 2Na(s) → 2CH3CH2O-Na+ (alc) + H2(g)

    • It can be used to test for alcohol
    • Sodium ethoxide
  8. What are the observation for the reaction between sodium and alcohol? (4 marks)
    • effervescence
    • the mixture gets hot
    • sodium dissolves in ethanol
    • a white solid is produced.
  9. What is the balanced equation for a reaction between phosphorus penta/(V) halide (chloride the halide in this case) and ethanol, what products are made and what type of reaction is this?
    • CH3CH2OH(l) + PCl5(s) → CH3CH2Cl(l) + POCl3(l) + HCl(g)
    • Chloroalkane and hydrogen gas
    • Subsitution
  10. How can you test for alcohol using phosphorus(V) chloride? ( 2 marks)
    • Reacting your alcohol with PCl5 will result in the formation of steamy fumes of HCl forming, which turn moist blue litmus paper red ( because the HCl dissovles to form a strong acid)
    •  HCl also dissolves in water to form chloride ions which presence can be tested using silver nitrate
  11. What the balanced equation for phosphorus(III) halide (iodide) and alcohol and what condition are need for it to be made
    • PI3 + 3CH3CH2OH → 3CH3CH2I + H3PO
    • In situ by refluxing the 'red phosphorus' in either bromine or iodine
  12. What happens when primary alcohols when they reacts with a limited amount of potassium dichromate?
    The alcohol turns into an aldehyde and water
  13. What happens when primary alcohols when they reacts with a excess amount of potassium dichromate?
    the alcohol turns into a aldehyde then a carboxylic acid.
  14. What the name of the apparatus used to prepare carboxylic acid from primary alcohols and what is it made up from? ( 4 marks)
    • Reflux apparatus
    • circle instead of pear
    • Liebig condenser
    • round bottom flask
  15. How do you conduct an experiment to get carboxylic acid from primary alcohol, what the advantage of using this technique and what observation is seen ? (4 marks)
    • Using a reflux apparatus 
    • Excess Potassium dichromate (VI) and dilute sulfuric acid is added with alcohol along with anti bumping granules to make the boiling smoother and is heated.
    • This allows violtile solvents to boil without being lost as any vapourised compounds are condensed and put back into the mixture
    • Orange dichromate solution changes to green colour
  16. What is the suffix used to describe a aldehyde
  17. What is the word equation required to form a carboxylic acid and what is the suffix for carboxylic acids?
    • Aldehyde + water → Carboxylic acid
    • oic acid
  18. What happen when a secondary alcohol and potassium dichromate( VI) react and what the observation seen?
    • A ketone is made with water
    • the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion
  19. What happen when a tertiary alcohol reacts with potassium dichromate (VI) and why?
    • No reaction
    • This is because there is no hydrogen atom bonded to the carbon with the OH group
  20. What the name of the technique that can be used to prepare a ketone from a secondary alcohol and how does it work? ( 2 marks)
    • Distillation
    • Secondary alcohol is heated with acidified potassium dichromate (VI) at a temperture above the boiling temperture of the ketone but below the boiling temperture of the secondary alcohol ensuring only the ketone reaches the receiving flask
  21. What the name of the technique that can be used to prepare a aldehyde from a from a primary alcohol and how does it work? (3 marks)
    • Distillation
    • Using a limited amount of potassium dichromate (VI) solution and dilute
    • sulphuric acid, you gently heat the flask until an apple smell is produced indicating an aldehyde has formed.
  22. How do you distinguish between a aldehyde and ketone alcohol and what is observed
    • React both with Fehlings/ Benedict solution.
    • Aldehydes :Blue Cu2+ ions in solution change to a brick red precipitate of Cu2O.
    • Ketones do not react