Question

When 20.0 mL of an acetic acid (CH3COOH) solution is titrated with a 0.0610 M sodium hydroxide (NaOH) solution, the equivalence point in the titration is 41.09 mL.

a) What was the concentration of acetic acid solution?

b) What are the [H3O+], [OH] and [CH3COO] at the equivalence point?

c) What is the pH at the equivalence point?

Note: The Ka for acetic acid (CH3COOH) is 1.74 × 10^-5.

Answer 1

Answer:

Solution that is 0.100 M CH3COOH (acetic acid)

and 0.100 M NaCH3COO (sodium acetate)

Find pH of buffer solution:

CH3COOH(aq) + H2O ↔ CH3COO-

(aq) + H3O+(aq)

[CH3COOH] [CH3COO-

] [H3O+]

initial 0.100 0.100 ≈0

-x x x

equil 0.100 – x 0.100 + x xFind pH of buffer solution:

CH3COOH(aq) + H2O ↔ CH3COO-

(aq) + H3O+(aq)

Ka = [CH3COO-

][H3O+

]

[CH 3COOH] = (.100 + x)x

(.100 - x) = 1.8 x 10-5

x = 1.80 x 10-5 M

pH = 4.7

Explanation: