Question

Larutan 50 mL Ch3COOH pH 3 (Ka = 10^-5) ditambah dengan 25 mL NaOH pH = 13. Nilai pH larutan akhir adalah...

A. 3
B. 5
C. 8
D. 12
E. 13

Answer 1

Jawaban:

B. 5

Penjelasan:

     CH3COOH         +   NaOH        ⇒ CH3COONa + H20

pH CH3COOH =-log [H+]

3 = - log

nCH3COOH = 0,1 × 50 = 5 mmol

POH NaOH = 14 - pH NaOH

POH = 1

pOH = -log[OH-]

[OH-] =

[OH-]=[NaOH]= 0,1 M

nNaOH = 0,1×25=2,5mmol

      CH3COOH         +   NaOH        ⇒ CH3COONa + H20

m       5 mmol                   2,5mmol        -                            -

r         2,5mmol                 2,5mmol        2,5 mmol        2,5 mmol

--------------------------------------------------- -    ------------------------------------+

s        2,5mmol                    -                   2,5mmol        2,5mmol

Tersisa asam lemah, jadi larutan termasuk buffer

[H+]=

[H+] =

pH = 5