Question

A chemist must prepare of hydrobromic acid solution with a pH of at . He will do this in three steps: Fill a volumetric flask about halfway with distilled water. Measure out a small volume of concentrated () stock hydrobromic acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrobromic acid that the chemist must measure out in the second step. Round your answer to significant digits.

Answer 1

Hello. This question is incomplete. The full question is:

A chemist must prepare 500.0mL of hydrobromic acid solution with a pH of 0.50 at 25°C. He will do this in three steps: Fill a 500.0mL volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (5.0M) stock hydrobromic acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrobromic acid that the chemist must measure out in the second step. Round your answer to significant digits.

Answer:

31.62 mL

Explanation:

To achieve this result, you must start by calculating the H + concentration. You will do this using the following formula:

pH = -log [H +]

0.50 = -log [H +]

[H +] = 10 ^ -0.50

[H +] = 0.31623 mol / L

After that you must consider that hydrobromic acid will have a weak capacity to disassociate, since it has a strong nature. In this case, we can consider that [HBr] = [H +] = 0.31623 mol / L.

After reaching this reason, it is necessary that you dilute the stock solution, using the formula:

C1V1 = C2V2

5.0 * V1 = 0.31623 * 500.0

V1 = 31.62 mL

And so you finish the answer.