Hello, I am taking a General Chemistry II course and I am having some trouble wi

Question

Hello, I am taking a General Chemistry II course and I am having some trouble with buffer problems. If you can explain a set of problems to me, I'm sure that it would help me out. I understand that a buffer can be found with a known pKa and that the pH can be found by using the Henderson-Hasselbalch equation, but I am not sure how to go about this with a given pH and volume, but no concentrations.

"You need to make 100 mL of a buffer with a pH of 9.00.
What acid-base pair will you use?
What is the ratio of acid to base concentrations you will use?
What amounts of the acid and base (either volume or mass) will you add to make the 100 mL of buffer solution? You can assume that the addition of solid compounds will not change the volume of the solution."

Explanation / Answer

There are many buffers with buffering capacity at pH 9.

ex: NH4OH+NH4Cl, phosphate buffer (Na2HPO4+Na3PO4), Glycine-NaOH and Boric acid-Borax buffer.

Glycine-NaOH buffer preparation:

0.2 M solution of Glycine (15.01 g in 1000ml)

0.2 M NaOH

50ml of 0.2M Glycine+8.8 ml of 0.2 M NaOH, and diluted to 200ml. This solution will maintaine exact pH -9.

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