Preparation and standardization of 0.5 M Sodium Hydroxide EP Volumetric Solution

1.  PREPARATION:

Dissolve 21 g of Sodium hydroxide in carbon dioxide free water and dilute to       1000 mL with the same solvent.

2. STANDARDISATION:

Dissolve 0.75 g of Potassium hydrogen phthalate in 50 mL of water. Titrate with the Sodium hydroxide solution, determining the end point Potentiometrically or using      0.1 mL of Phenolphthalein solution as indicator.

1 mL of 0.5 M Sodium hydroxide is equivalent to 102.1 mg of C₈H₅KO₄.

Calculation:

 Molarity (M) = [0.5 x Weight of Potassium hydrogen phthalate (in g)]/[0.1021 x Titration reading (in mL)]                         

Limit: 0.5 M ± 5 % (0.4750 M – 0.5250 M)

3. PREPARATION OF INDICATORS / REAGENTS:

a. Phenolphthalein solution :

Dissolve 0.1 g of Phenolphthalein in 80 mL of Ethanol (96 %) and dilute to 100 mL with water.

4. STORAGE CONDITION:

Store in glass stoppered bottles.