I have 1 last Q that I am stuck on & I would really

• Pawesome1234

  29 Oct 12, 01:53

  I would really appreciate help.

  QUESTION - 
  One of the students was in a hurry to finish and filtered his solution in step 4 before it had cooled down properly.Explain why this resulted in him obtaining a low yield.

   

  I'm really unsure please help.
  
  
  Hydrolsis ester - PROCEDURE
  
  1.Add 2cm3 of methylbenzoate flask, record mass
  Add 10cm3 dilute 2.0moldm-3 NaOH solution (in excess), about 10cm3 of ethanol and anti bump granules. fit the water condesner on
  
  2. heat flask gently without allowing contents to boil for about 5 min. and then boil gently under reflex for futher 15 min
  
  3. allow contents flask to cool remove condenser and decant solution from antibump graniles into a beaker. add 10 drops methyl orange indicator and acidify with 2.0 moldm-3 HCl. filter product under reduced pressure
  
  4. recrstyallise product - dissolve solid in minim amount of boiling water to allow to cool slowly, when cool filter purified product under reduced pressure and allow dry in air on filter paper
  
  5. dry sample of product by pressing between filter papers and determine mpt (which is greater than 100 degrees) record value
  
  6. weigh dry product and record mass

• UltimaOnline

  29 Oct 12, 02:06

  Jennifergriffiths2210 aka Pawesome1234, pls keep your posts to a single thread. And indicate the subject in your title.

  A significant amount of benzoic acid remains dissolved in the (still hot) solution, instead of crystallizing out.

  Originally posted by Pawesome1234:

  
  I would really appreciate help.

  QUESTION - 
  One of the students was in a hurry to finish and filtered his solution in step 4 before it had cooled down properly.Explain why this resulted in him obtaining a low yield.

   

  I'm really unsure please help.
  
  
  Hydrolsis ester - PROCEDURE
  
  1.Add 2cm3 of methylbenzoate flask, record mass
  Add 10cm3 dilute 2.0moldm-3 NaOH solution (in excess), about 10cm3 of ethanol and anti bump granules. fit the water condesner on
  
  2. heat flask gently without allowing contents to boil for about 5 min. and then boil gently under reflex for futher 15 min
  
  3. allow contents flask to cool remove condenser and decant solution from antibump graniles into a beaker. add 10 drops methyl orange indicator and acidify with 2.0 moldm-3 HCl. filter product under reduced pressure
  
  4. recrstyallise product - dissolve solid in minim amount of boiling water to allow to cool slowly, when cool filter purified product under reduced pressure and allow dry in air on filter paper
  
  5. dry sample of product by pressing between filter papers and determine mpt (which is greater than 100 degrees) record value
  
  6. weigh dry product and record mass