Sodium hydroxide prepared and can be standardized by acid base titration methods using Potassium Hydrogen Phthalate as a primary standard.

1. Standardization of Sodium
Hydroxide Solution
Presented By
Mrs.Smita P.Shelke
Assistant Professor, Department of Pharmaceutical Chemistry,
GES’s Sir Dr.M.S.Gosavi College of Pharmaceutical Education and
Research, Nashik-05.(Maharashtra

2. Experiment No: 01
Title: To prepare and standardization of 0.1 M sodium hydroxide
solution (NaOH) using the primary standard potassium hydrogen
phthalate.

3. Requirements
• Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker,
volumetric flask, funnel, glass rod, and wash bottle, etc.
• Chemicals: LR grade sodium hydroxide (NaOH), potassium hydrogen
phthalate (KHP), and phenolphthalein indicator, etc.
• Apparatus: Digital/analytical balance, and Ultrasonicator.

4. Theory:
To determine the exact concentration (Molarity/Normality) of NaOH solution
it needs to be standardized. Because solid NaOH is extremely hygroscopic, it
cannot be precisely weighed. The concentration of sodium hydroxide may be
determined extremely precisely by titrating a KHP sample of known
mass/mole with the NaOH solution.

5. Principle
Potassium hydrogen phthalate is directly titrated with sodium hydroxide to
determine its strength. Using phenolphthalein as an indication, the endpoint of
the titration is determined. The following is the reaction that is involved in this
titration.

6. Principle

7. Factor calculation
1mole of NaOH eqivalent to 1 mole of KHP
40 g of NaOH ≡ 204.2 g of KHP
1000 ml of 1 M NaOH ≡ 204.2g of KHP
100 ml of 1 M NaOH ≡ 20.42g of KHP
10 ml of 1 M NaOH ≡ 2.042g of KHP
1 ml of 1 M NaOH ≡ 0.2042g of KHP
1 ml of 0.1 M NaOH ≡ 0.02042 g KHP

8. Preparation of 0.1 M NaOH
The molecular weight of sodium hydroxide (NaOH) is 39.997 g/mol
40 g in 1000 ml solvent is 1 M solution
4 g in 1000 ml solvent is 0.1 M sloution
0.4 g in 100 ml solvent is 0.1 M
Procedure:
1. Weigh accurately 04.00 gm of sodium hydroxide in watch glass.
2. Add 50 ml of distilled water to it.
3. Mix it well.
4. Make up the volume upto 100 ml with distilled water.

9. Titration Procedure
1. All glassware should be cleaned and dried according to standard laboratory
procedures.
2. 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.
3. Take the sodium hydroxide stock solution of titrant in a clean and dry beaker
then fill the burette using the funnel.
4. Remove air bubbles from the burette and adjust the reading to zero.

10. Titration Procedure
5. Accurately weigh 0.2 gm of previously dried potassium hydrogen phthalate
and pour into a conical flask.
6. To dissolve adequately, add 25 ml distilled water and sonicate for 5 minutes
on a sonicator.
7. Add 2 drops of phenolphthalein indicator once it has been solubilized.
8. Titrate the sample solution with NaOH until the endpoint is reached. A pink
color appears and disappears, indicating that the endpoint is approaching, when
the solution is swirled for up to 10 seconds. The actual endpoint is indicated by
a pink color that lasts longer than 30 seconds.

11. Titration Procedure
9. Properly record the readings of the burette.
10. To get accurate results, repeat the titration three times.
11. Take their mean and calculate the molarity of NaOH.

12. Observations
Solution in Burette: Sodium hydroxide
Conical flask: 0.2 g of KHP in 25 ml DW
Indicator: Phenolpthalein
Colour Change: Colorless to Pink
Constant Burette readings:
Sr. No. Burette reading Volume of
titrant
1
2
3
Mean

13. Calculations:
1 ml of 0.1 M NaOH ≡ 0.02042 g KHP
C B R ml of X M NaOH = 0.2 g of KHP
Cross multiplication
1 x 0.1 x 0.2 = Avg C B R x X M x 0.02042
1 x 0.1 x 0.2
X M = ------------------------------------------
Avg C B R x 0.02042

14. Result:
The molarity of prepared sample of sodium hydroxide was found to be
--------------------- M.