Final answer:
To prepare 250 mL of a 0.225% NaCl solution, you would measure 0.868 mL of a 0.65% stock solution and dilute it with distilled water to a final volume of 250 mL.
Step-by-step explanation:
To prepare 250 mL of a 0.225% (m/v) NaCl solution from a 0.65% (m/v) NaCl stock solution, we need to calculate how much of the stock solution is required and then dilute it with distilled water. No additional NaCl stock solution, ethanol, or sodium bicarbonate is required. The process involves a dilution calculation using the formula C1V1 = C2V2, where C1 is the concentration of the stock solution, V1 is the volume of the stock solution needed, C2 is the desired concentration, and V2 is the final volume of the solution.
Applying the formula:
-
- C1 = 0.65% (m/v)
-
- C2 = 0.225% (m/v)
-
- V2 = 250 mL
We solve for V1:
V1 = (C2 * V2) / C1 = (0.225% * 250 mL) / 0.65% = 0.868 mL (approximately)
Next, measure 0.868 mL of the stock solution using a pipette and add it to a volumetric flask. Then add distilled water to the flask until the final volume reaches 250 mL. This will give you the desired 0.225% NaCl solution.