In a titration of an acetic acid (CH_3COOH) solution of unknown concentration, a

Question

In a titration of an acetic acid (CH_3COOH) solution of unknown concentration, a 28.18 mL sample of the acid is required 28.73 mL of a 0.2110 mol/L KOH solution to reach the equivalence point. a) Determine the initial concentration of CH_3COOH. b) What ions are present in significant concentrations in the solution at the equivalence point? Support your answer with the appropriate balanced chemical equations. c) What is the concentration of the conjugate base at the equivalence point? d) What is the percent dissociation, given an initial pH of 2.82? e) Determine the pH of the solution at the equivalence point. Calculate the volume of 0.500 mol/L sodium formate, NaHCOO, solution that should be mixed with 100 mL of 0.250 mol/L formic acid, HCOOH, to prepare a buffer solution having a pH of 3.53. (K_a for formic acid is 2.00 middot 10^-4)

Explanation / Answer

18)

a)

volume of acid = 28.18 mL

At equivalence point :

millimoles of acid = millimoles of KOH

28.18 x M = 28.73 x 0.2110

M = 0.2151

initial concentration of CH3COOH = 0.2151 M

b)

At equivalence point :

CH3COO- is present.

[CH3COO-] = 28.73 x 0.2110 / 28.73 + 28.18 = 0.1065 M

concentration of [CH3COO-] = 0.1065 M

c)

concentration of conjugate base at equivalence point = 0.1065 M

d)

pH = 2.82

[H+] = 1.514 x 10^-3 M

C = 0.2151 M

% ionization = 1.514 x 10^-3 / 0.2151 ) x 100

                    = 0.704 %

e)

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

     = 7 + 1/2 (4.74 + log 0.1065)

     = 8.88

pH = 8.88

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.