Final answer:
To prepare 40 mL of a 0.12 M acetic acid solution, measure 0.8 mL of a 6 M acetic acid stock solution and dilute it with water until the total volume is 40 mL.
Step-by-step explanation:
To prepare 40 mL of 0.12 M acetic acid (HC2H3O2) from a 6 M stock solution, we need to use the dilution formula M1V1 = M2V2, where M1 is the concentration of the stock solution, V1 is the volume of the stock solution to be diluted, M2 is the desired concentration, and V2 is the desired final volume of the diluted solution. Plugging in the given values: (6 M) * V1 = (0.12 M) * (40 mL), we can find V1:
V1 = (0.12 M * 40 mL) / 6 M = 0.8 mL.
Therefore, to create the desired solution, you would measure 0.8 mL of the 6 M acetic acid and dilute it with water to a final volume of 40 mL. It's important to add the acetic acid to water rather than the other way around to ensure proper mixing and safety.