How to Prepare a 5 ppm Sodium Arsenate Solution: A Step-by-Step Guide

Accurately preparing a 5 ppm sodium arsenate (Na3AsO?3-) solution involves precise measurements and careful preparation. This article walks you through the process of making a 5 milligram per liter (5 ppm) solution in a volumetric flask, from initial preparation to final solution dilution.

Understanding the Fundamental Concept

The notation of 5 ppm (parts per million) is commonly used in environmental science, chemistry, and other fields to denote the concentration of a substance. Specifically, 5 ppm means that there are 5 milligrams of sodium arsenate in one liter of aqueous solution.

Step-by-Step Procedure for Preparation

Step 1: Preparation of the Initial Solution

Start by accurately weighing 5.00 grams of sodium arsenate salt (Na3AsO?3-). Ensure that the balance is calibrated and free from any contaminants. Transfer the sodium arsenate salt to a volumetric flask that has a total volume of 1 liter. Add a small amount of distilled water to the volumetric flask to cover the sodium arsenate salt, and then gently swirl the flask to initiate dissolution. Slowly and carefully add distilled water to the volumetric flask until the bottom of the meniscus is level with the 1-liter mark. This will create a 5000 ppm (5000 mg/L) sodium arsenate solution.

Step 2: Dilution to Achieve the Desired Concentration

Now that you have prepared a 5000 ppm solution, take an exact 1 milliliter (mL) sample of this solution using a precision pipette. Transfer the 1 mL sample into a clean volumetric flask with a volume of 1 liter. If necessary, use a funnel to ensure that the sample is accurately placed in the volumetric flask. Fill the volumetric flask to the mark with distilled water, making sure to thoroughly mix the solution until it is homogeneously distributed. The final solution will now be a 5 ppm sodium arsenate solution (5 mg/L).

Conclusion

Preparing a 5 ppm sodium arsenate solution requires precision in handling and accurate measurements. By following the steps outlined in this guide, you can ensure the creation of a solution that meets the required concentration for various applications, including environmental testing and laboratory experiments.

Key Takeaways

5 ppm means 5 milligrams of sodium arsenate salt in 1 liter of solution. Start with a 5000 ppm solution and dilute it to achieve the desired 5 ppm concentration. Use a volumetric flask for accurate volume measurements. Ensure the final solution is well mixed to achieve uniform concentration.

References

For further information and detailed technical specifications, refer to:

Arsenic in Drinking Water: An Overview of Monitoring and Management U.S. EPA Guidelines for Arsenic in Drinking Water