Final answer:
To prepare a 250 mL dilution of 2.35 M HF from a 15.0 M solution, you need to take 39.2 mL of the 15.0 M HF solution and dilute it with enough water to make the final volume 250 mL.
Step-by-step explanation:
To prepare a 250 mL dilution of 2.35 M HF from a 15.0 M solution, you can use the formula C1V1 = C2V2. Rearranging the formula to isolate the desired parameter, we have V1 = (C2V2) / C1. Plugging in the values, we get V1 = (2.35 M)(0.250 L) / 15.0 M = 0.0392 L or 39.2 mL. Therefore, you need to take 39.2 mL of the 15.0 M HF solution and dilute it with enough water to make the final volume 250 mL.