0.1 M EDTA Solution Preparation and Standardization
Introduction
EDTA (Ethylene Diamine Tetraacetic Acid) is a commonly used chelating agent in analytical chemistry, particularly in complexometric titrations. EDTA solution is essential in determining the concentration of metal ions, such as calcium and magnesium, in aqueous samples. In this article, we will discuss the preparation and standardization of 0.1 M EDTA solution.
Preparation of 0.1 M EDTA Solution
Materials Needed
- EDTA (Ethylene Diamine Tetraacetic Acid)
- Distilled water
- pH indicator (e.g., phenolphthalein)
- Sodium hydroxide (NaOH)
Procedure
- Weighing: Weigh accurately 3.72 g of EDTA (MW = 372.24 g/mol) and transfer it to a 100 mL beaker.
- Dissolving: Add approximately 80 mL of distilled water to the beaker and stir until the EDTA is completely dissolved.
- pH Adjustment: Add a few drops of pH indicator (e.g., phenolphthalein) to the solution. The pH of the solution should be around 5-6. If the pH is lower than 5, add a small amount of sodium hydroxide (NaOH) solution (0.1 M) dropwise until the pH reaches 5-6.
- Volume Adjustment: Add distilled water to the beaker to make the final volume of 100 mL.
- Mixing: Stir the solution well to ensure complete mixing.
Standardization of 0.1 M EDTA Solution
Principle
The standardization of EDTA solution is based on the reaction between EDTA and calcium ions. Calcium carbonate (CaCO3) is used as the primary standard.
Materials Needed
- 0.1 M EDTA solution (prepared above)
- Calcium carbonate (CaCO3)
- Distilled water
- pH indicator (e.g., methyl orange)
- Sodium hydroxide (NaOH)
Procedure
- Weighing: Weigh accurately 0.25 g of calcium carbonate (CaCO3) and transfer it to a 100 mL beaker.
- Dissolving: Add approximately 50 mL of distilled water to the beaker and stir until the CaCO3 is completely dissolved.
- pH Adjustment: Add a few drops of pH indicator (e.g., methyl orange) to the solution. The pH of the solution should be around 10-11. If the pH is lower than 10, add a small amount of sodium hydroxide (NaOH) solution (0.1 M) dropwise until the pH reaches 10-11.
- Titration: Add the prepared 0.1 M EDTA solution to the CaCO3 solution until the end point is reached, as indicated by the pH indicator.
- Calculation: Calculate the exact concentration of the EDTA solution based on the volume of EDTA solution required to reach the end point.
Formula
EDTA (0.1 M) = (Weight of CaCO3 x Molarity of CaCO3) / (Volume of EDTA required x Molarity of EDTA)
where Molarity of CaCO3 = 0.01 M and Molarity of EDTA = 0.1 M
Conclusion
In this article, we have discussed the preparation and standardization of 0.1 M EDTA solution. The standardization of EDTA solution is essential to ensure the accuracy of complexometric titrations. By following the procedures outlined above, you can prepare and standardize 0.1 M EDTA solution for use in your analytical chemistry experiments.
