I asked a teacher for help, but they told me we didnt need to do these 2 Q but I want to do them anyway.
QUESTION -
a student 3 added 20cm3 of the 2moldm-3 NaOH instead of 10cm^3 by accident. should they have started again? why
AND student 4 only added 5cm3 of the NaOH instead of 10cm3. Show by calculation that student 4 did not have an excess of sodium hydroxide
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
Student 3 : No need to restart, since NaOH is to be in excess anyway.
Student 4 :
You need either the molarity (if ester solution was used) or density (if pure ester was used), to work out the moles of ester to be hydrolyzed.
The stoichiometry for base promoted hydrolysis of ester is 1 : 1.
From molarity and volume of NaOH used, you can determine if the ratio of NaOH to the ester is more than one (ie. excess NaOH) or less than one (ie. excess ester).
Originally posted by Pawesome1234:I asked a teacher for help, but they told me we didnt need to do these 2 Q but I want to do them anyway.
QUESTION -
a student 3 added 20cm3 of the 2moldm-3 NaOH instead of 10cm^3 by accident. should they have started again? why
AND student 4 only added 5cm3 of the NaOH instead of 10cm3. Show by calculation that student 4 did not have an excess of sodium hydroxide
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