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1) What is the pH at the equivalence point in the titration of a 21.9 mL...

1) What is the pH at the equivalence point in the titration of a 21.9 mL sample of a 0.456 M aqueous hypochlorous acid solution with a 0.494 M aqueous potassium hydroxide solution?

pH =

2) When a 29.8 mL sample of a 0.430 M aqueous hydrocyanic acid solution is titrated with a 0.373 M aqueous potassium hydroxide solution, what is the pH after 51.5 mL of potassium hydroxide have been added?

pH =

Solutions

Expert Solution

millimoles of HClO = 21.9 x 0.456 = 9.9864

At equivalence point :

mmoles of acid = mmoles of KOH

9.9864 = 0.494 x V

V = 20.22 mL

here salt only remains.

salt concentration = 9.986 / (21.9 + 20.22) = 0.237 M

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

= 7 + 1/2 (7.46 + log 0.237)

pH = 10.42

mmoles of HCN = 29.8 x 0.430 = 12.814

mmoles of KOH = 51.5 x 0.373 = 19.2095

HCN + KOH --------> KCN + H2O

12.8 19.2 0 0

0 6.40 12.8

here strong base reamins.

[OH-] = 6.40 / 29.8 + 51.5 = 0.0787 M

pOH = 1.10

pH = 12.90

queen_honey_blossom answered 7 months ago

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