0.1 M Ethanolic Sodium Hydroxide Standardization
Introduction
Sodium hydroxide (NaOH) is a strong base commonly used in various analytical techniques, including titration. However, its concentration can vary depending on the source and storage conditions. To ensure accurate results, it is essential to standardize the sodium hydroxide solution. Ethanol is often used as a solvent to prepare a 0.1 M sodium hydroxide solution, which is then used for standardization. In this article, we will outline the procedure for standardizing a 0.1 M ethanolic sodium hydroxide solution.
Materials
- 0.1 M sodium hydroxide solution in ethanol
- Potassium hydrogen phthalate (KHP) crystals
- Distilled water
- pH meter
- Burette
- Conical flask
Principle
The standardization of 0.1 M ethanolic sodium hydroxide is based on the reaction between NaOH and potassium hydrogen phthalate (KHP):
NaOH + HKC₈H₄O₄ → NaKC₈H₄O₄ + H₂O
The reaction is quantitative, and the amount of NaOH required to neutralize a known weight of KHP is directly proportional to the concentration of NaOH.
Procedure
Step 1: Preparation of KHP Solution
Weigh accurately about 0.5-1.0 g of KHP crystals into a conical flask. Add about 50 mL of distilled water and stir until the KHP is completely dissolved.
Step 2: Titration
Pipette a 10-20 mL aliquot of the KHP solution into a conical flask. Add a few drops of phenolphthalein indicator and titrate with the 0.1 M ethanolic sodium hydroxide solution until the color changes from colorless to pink.
Record the volume of NaOH solution required to reach the endpoint.
Step 3: Calculation
The molarity of the sodium hydroxide solution can be calculated using the following formula:
Molarity of NaOH = (Weight of KHP in g / 204.22) / Volume of NaOH in L
Where 204.22 is the molecular weight of KHP.
Step 4: Validation
Repeat the titration at least three times to validate the results. The average molarity of the sodium hydroxide solution should be calculated and used for future titrations.
Tips and Precautions
- Use high-quality KHP crystals to ensure accurate results.
- Handle the ethanolic sodium hydroxide solution with care, as it can cause skin and eye irritation.
- Ensure the pH meter is calibrated before use.
- Perform the titration in a well-ventilated area to prevent ethanol vapor accumulation.
By following this procedure, you can accurately standardize a 0.1 M ethanolic sodium hydroxide solution, which can be used for various analytical applications.
