3. 1 -0 points ZumChemP7 8.E.069. Calculate the pH at the halfway point and at t

Question

3. 1 -0 points ZumChemP7 8.E.069. Calculate the pH at the halfway point and at the equivalence point for each of the following titrations. (Assume that the temperature is 25°C.) (a) 101.9 mL of 0.1 7 M HCO2H (Ka. 1.8×10-4) titrated with 017 M KOH halfway point equivalence point (b) 103.3 mL of 0.19 M (C2HS)3N (K“ 4.0 x 10-4) titrated with 0.38 M Ha halfway point equivalence point (c) 100.8 mL of 0.55 M HCI titrated with 0.28 M KOH halfway point equivalence point Need Help? Ww Supporting Materials Constants and Factors Periodic Table Supplemental Data

Explanation / Answer

a)

pKa = 3.74

At half - equivalence point : pH = pKa

At half - equivalence point : pH = 3.74

At equivalence point : salt only remains.

salt concentration = 101.9 x 0.17 / 2 x 101.9 = 0.085 M

pH = 7 + 1/2 (pKa + log C)

    = 7 + 1/2 (3.74 + log 0.085)

pH = 8.34

At equivalence point : pH = 8.34

b)

pKb = 3.40

At half - equivalence point : pH = 10.60

At equivalence point : pH = 5.75

c)

At half - equivalence point : pH = 0.86

At equivalence point : pH = 7.00

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