A dilute aqueous solution of boric acid, H₃BO₃ is often used as an eyewash. How would you prepare 500.0 mL of a 0.50% (m/v) boric acid solution?

Verified step by step guidance

1. Step 1: Understand the concept of % (m/v). The percentage mass/volume (% m/v) is defined as the mass of solute (in grams) per 100 mL of solution. For a 0.50% (m/v) solution, this means 0.50 g of boric acid is dissolved in 100 mL of solution.
2. Step 2: Determine the total mass of boric acid needed for 500.0 mL of solution. Since the solution is 0.50% (m/v), scale up the mass proportionally: (0.50 g / 100 mL) × 500.0 mL.
3. Step 3: Weigh the calculated mass of boric acid using a balance. Ensure the balance is properly calibrated for accurate measurement.
4. Step 4: Dissolve the measured boric acid in a volume of distilled water that is less than 500.0 mL. Stir the solution until the boric acid is completely dissolved.
5. Step 5: Transfer the solution to a 500.0 mL volumetric flask and add distilled water until the total volume reaches exactly 500.0 mL. Mix thoroughly to ensure a uniform solution.

Key Concepts

Concentration (m/v)

Mass/volume (m/v) concentration expresses the mass of solute per 100 mL of solution. A 0.50% (m/v) solution means there are 0.50 grams of solute (boric acid) in every 100 mL of solution. This concept is crucial for understanding how to prepare solutions with specific concentrations.

Dilution

Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent. In this case, to prepare a 0.50% (m/v) solution from a more concentrated stock solution, one must calculate the appropriate volume of stock solution and the amount of water needed to achieve the desired concentration.

Measurement and Units

Accurate measurement is essential in preparing solutions. Understanding units such as grams for mass and milliliters for volume is necessary to ensure the correct proportions are used. This knowledge helps in converting between different units and ensuring the final solution meets the specified concentration.