Q.

20 mL of 0.1 M NaOH is added to 50 mL of 0.1 M acetic acid solution. The pH of the resulting solution is ________ ×10-2 (Nearest integer)

Given:  pKa(CH3COOH) = 4.76

              log 2 = 0.30

              log 3 = 0.48                                     [2023]


Ans.

(458)

                      NaOH    +     CH3COOHCH3COONa+H2O

                      0.1 M, 20 ml    0.1 M, 50 ml

Millimole=0.1×20=2,    0.1×50=5

                        L.R.=NaOH

So                 0                     5-2=(3)                           (2)

So resultant solution is an acidic buffer solution

So pH=pKa+log(saltacid)

pH=4.76+log23

pH=4.76+(-0.18)=4.58=458×10-2