September 2, 2014
Stock Solution Preparations and Titrant Standardization
Preparation of Stock Solution:
0.15 M NaOH was prepared from 3.00g of NaOH and then diluted to 500 mL with H2O.
- This molarity was chosen because NaOH is hygroscopic and the final concentration will not be able to be measured accurately.
- Because of this property NaOH cannot be used as a primary standard.
Tirant Standardization:
Potassium Hydrogen Phthalate (KHPhth) is used a standard for NaOH.
- Approximately 0.501 g of KHPhth was mixed with 17 mL of water and titrated with NaOH stock solution. Phenolphthalein was used as an indicator and only 5 drops was added. This process was repeated two additional times and approximately the same results were yielded.
- The final concentration of NaOH was found by averaging the results from the three trials.
- Final NaOH concentration is 0.1485 M.
NOTE The final concentration was averaged because the results were similar for all three trials.<br.>
| Trial #
|
KHPhth (g)
|
NaOH (mL)
|
| 1
|
0.501
|
16.70
|
| 2
|
0.518
|
17.10
|
| 3
|
0.519
|
17.10
|
Isoleucine Titration: Hydrophobic
Using the final concentration of 0.1485 M NaOH stock solution, the amount of isoleucine was calculated to yield 20 mL.
- 0.3896 g of Isoleucine was dissolved in 10 mL of H2O and 10 mL of 21 mM HCl
- The initial pH of the isoleucine solution is 3.351.
- NaOH was titrated against the isoleucine solution in 2 mL intervals and the pH tested until the pH reached around 10.
NOTE The pH meter that was used was calibrated using buffers solutions of pH 4,7,and 10.
|
Project name
