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determine the equivalence point volume, half equivalence point volume and pKa fo

ID: 987696 • Letter: D

Question

determine the equivalence point volume, half equivalence point volume and pKa for this sample titration. I think it should be around 10.5ml because that it where it starts to jump but I want to make sure. Here is the data from the book.

Volume, mL Derivative 0.001 0.000 0.003 0.000 0.002 1.613 11.502 1.578 0.001 0.002 Time, s pH 0.010 35.951 60.248 79.489 103.245 142.564 151.316 187.662 222.138 268.715 3.01 3.95 4.48 4.64 5.08 5.42 7.97 10.42 11.00 0.03 1.82 5.35 5.50 8.51 9.67 11.05 11.69 12.50 13.22 md es ully ev 12 00t - …… 11.00 10 00 12 00 11 00 10 00 8.00 7 00 7 00 5 00 4 00 : 00 3 00 2 00 1.00 2 00 1 00 0 00 0 50 100 1 50 2.00 2 50 300 350 4 0050 5 00 5 50 6 00 6.50 700 7 50 8.00 850 9 00 9 50 10 00 11 00 12 00 1300 14 00 aOH Volume mL

Explanation / Answer

From graph equivalence point of titration is at pH = 8.0

half equivalence point for titration is at pH = 4.6

pKa = pH at half equivalence point

So pKa = 4.6