How do you prepare 0.002 N Na2S2O3?

To prepare a 0.002 N Na2S2O3 (sodium thiOSulfate) solution, first calculate the required amount of sodium thiOSulfate pentahydrate (Na2S2O3·5H2O) needed, which has a molar mass of approximately 248.18 g/mol. For a 1-liter solution, you would need 0.002 equivalents per liter, which is equivalent to 0.002 moles of Na2S2O3. Dissolve 0.496 mg (0.000496 g) of the salt in distilled water and dilute to the final volume of 1 liter. Always ensure proper mixing and label the solution accurately.