User:Michael S. Bible/Notebook/571/2014/09/02

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Creating a Sodium Hydroxide Titrant and Performing a Standardization Titration

In order to create titration curves for our selected amino acids(Glycine, L-Lysine, L-Cysteine, L-Glutamine, and L-Tryptophan), we need to create a titrant solution of Sodium Hydroxide that is approximately .15M. To do this, we need to mix 3 g NaOH with 500 mL water. We will then perform a standardization titration by titrating Potassium Hydrogen Phthalate (KH(Phth)) and an indicator (Phenolphthaline) with the Sodium Hydroxide solution that we create.

Creating Stock NaOH Solution

A stock NaOH solution was created using:

  • 3.0772 g NaOH
  • 500 mL Water

Standard Titration Data

A standard titration was performed three times. The specific quantities of each substance used, and the data collected can be found in the table below.

  • Note that 3 drops of Phenolphthaline were used in each experiment and titrations were done until the solution turned uniformly pink in color.


Standardization Titrations.png

Standardization Titrations reveal that the actual Molarity of the NaOH solution created is .148M NaOH.

First Round Titrations

Simple titrations of each amino acid were done using 4 mL increments of NaOH to get an idea of what the titration curve would look like and better prepare to collect data from a second trial. Amino acids were prepared in erlynmeyer flasks with 10 mL of water and 1 mL of 21 mM HCl (Note for L-Tryptophan, 20 mL of water and 2mL of 1M HCl were used). The masses of amino acids used can be found in the table below.


Amino Acid Mass (g)
L-Cysteine 0.3546
L-Lysine 0.54112
L-Glutamine 0.43501
L-Tryptophan 0.61280
Glycine 0.22570

It is worth noting that this experiment was a single-calibration titration. The results for each amino acid are as follows: L-Cysteine

NaOH (mL) pH
0 3.11
4 7.51
8 8.02
12 8.35
16 8.67
20 9.18

L-Lysine

NaOH (mL) pH
0 9.08
4 9.35
8 9.68
12 9.98
16 10.24
20 10.58

L-Tryptophan

NaOH (mL) pH
0 2.06
4 2.46
8 2.85
12 3.42
16 8.46
20 8.99

L-Glutamine

NaOH (mL) pH
0 3.38
4 8.31
8 8.82
12 9.20
16 9.54
20 10.34

Glycine

NaOH (mL) pH
0 2.45
4 2.94
8 8.22
12 9.13
16 9.50
20 9.83