An unknown triprotic acid (H3A) is titrated with NaOH. After the titration Ka1 is determined to be 0.0013 and Ka2 is determined

Question

3 years ago

11

to be 6.5e-07. The pH at the second equivalence point of the titration is measured as 8.181. What is Ka3 for this triprotic acid

1 answer:

e-lub [12.9K] · Answer 1 · 2022-06-12T03:23:42+03:00

Answer:

6.68 X 10^-11

Explanation:

From the second Ka, you can calculate pKa = -log (Ka2) = 6.187

The pH at the second equivalence point (8.181) will be the average of pKa2 and pKa3. So,

8.181 = (6.187 + pKa3) / 2

Solving gives pKa3 = 10.175, and Ka3 = 10^-pKa3 = 6.68 X 10^-11