This question has multiple parts. Work all the parts to get the most points. Cal

Question

This question has multiple parts. Work all the parts to get the most points. Calculate the pH at the halfway point and at the equivalence point for each of the following titrations. 100.0 mL of 0.70 M HC,H2 (Ka pH at the halfway point- pHI at the equivalence point 6.4 x 10-5) titrated by 0.10 M NaOH Submit 100.0 mL of 0.70 M C2H5 NH2 ( Kb pH at the halfway point pH at the equivalence point- 5.6 x 10-4 ) titrated by 0.60 M HNO3 100.0 mL of 0.60 M HCl titrated by 0.15 M NaOH pH at the halfway point pH at the equivalence point-

Explanation / Answer

a)

mmoles of HC7H5O2 = 100 x 0.70 = 70

Ka = 6.4 x 10^-5

pKa = 4.19

At half way point : pH = pKa

At half way point : pH = 4.19

At equivalence point : salt remains.

salt concentration = 70 / 100 + 700 = 0.0875 M

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

     = 7 + 1/2 (4.19 + log 0.0875)

At equivalence point : pH = 8.57

b)

pKb = 3.25

pKa = 10.75

at half way point : pH = 10.75

At equivalence point : pH = 5.62

c)

mmoles of HCl = 100 x 0.60 = 60

mmoles of NaOH = 200 x 0.15 = 30

[H+] = 60 - 30 / 100 + 200 = 0.1 M

pH = 1.00

At half way point : pH = 1.00

At equivalence point : pH = 7.00

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