Learn about the preparation and standardization of 0.1 M tetrabutylammonium hydroxide solution through a laboratory experiment or practical.
Aim:
To prepare and standardize 0.1 M tetrabutylammonium hydroxide solution using benzoic acid as primary standard (Non-aqueous titration).
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.
Chemicals: Tetrabutylammonium iodide (C16H36IN), methanol (CH3OH), silver oxide (Ag2O), benzoic acid (C7H6O2), dimethylformamide (C3H7NO), thymol blue indicator, and toluene (C6H8), etc.
Preparation of 0.1 M tetrabutylammonium hydroxide solution:
- Take 40.00 g of tetrabutylammonium iodide, pour into a glass flask and add 90.00 ml of methanol (dehydrated) to dissolve.
- Put it in an ice bath, add 20.00 g of silver oxide (powdered), close the lid, and agitate vigorously for 1 hour.
- Test the supernatant liquid for iodides after centrifuging a few ml. (To test for iodides: add 00.50 ml of mercuric chloride solution to 01.00 ml of this solution; if a dark red precipitate forms, the test is positive for iodide).
- If the test is positive, add another 02.00 gm of silver oxide and let it stand for another 30 minutes with intermittent agitation.
- Once all the iodide has reacted, filter it through a fine sintered-glass filter.
- Rinse the flask and filter with three volumes of toluene (anhydrous), 50.00 ml each.
- Add the filtrate washings and dilute with toluene to 1000 ml.
- For 10 minutes, flush the solution with dry, carbon dioxide-free nitrogen.
- Store it in an airtight container away from carbon dioxide and moisture and use it for up to 60 days.
Titration procedure:
- All glassware should be cleaned and dried according to standard laboratory procedures.
- Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
- Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
- Remove air bubbles from the burette and adjust the reading to zero.
- Take 0.4 gm of benzoic acid, properly weighed, and dissolved in 80.00 ml of dimethylformamide.
- Add a few drops of a 1 % w/v solution of thymol blue.
- Perform the titration with tetrabutylammonium hydroxide solution until the end-point.
- The blue color indicates the blue endpoint of the titration.
- Make any necessary corrections after performing a blank determination.
- During the titration, protect the solution from atmospheric carbon dioxide
- To get accurate results, repeat the titration three times.
- Properly record the readings of the burette.
- Take their mean and calculate the molarity of the tetrabutylammonium hydroxide solution.
Observation table:
|
Sr.
No. |
Content
in conical flask |
Burette
reading |
Volume
of titrant used (ml) |
|
|
Initial |
Final |
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|
1 |
|
|
|
|
|
2 |
|
|
|
|
|
3 |
|
|
|
|
|
|
Mean: |
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Calculations:
1 ml of 0.1 M tetrabutylammonium hydroxide is equivalent to 0.01221 g of C7H602.
M = weight of C7H6O2 x 0.1 / 0.01221 x volume of titer (ml) of 0.1 M tetrabutylammonium hydroxide
Result:
The strength of the prepared tetrabutylammonium hydroxide solution was found to be_____M.
Frequently Asked Questions (FAQ):
What is the molecular mass of c16h37no?
The molecular weight of tetrabutylammonium hydroxide (C16H37NO) is 259.47
Which indicator is used in the standardization of 0.1 M tetrabutylammonium hydroxide?
Thymol blue indicator is used to standardize 0.1 M tetrabutylammonium hydroxide which produce blue color at the endpoint of reaction.
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