Question

100 ml of 0.1 m sodium acetate solution has a ph of 8.90. to this solution 1000 μl of 1m acetic acid (pka = 4.76) of ph (2)80 is added. the ph of this mixture will be

Answer 1

Answer: 5.76

Explanation:

[Salt] --> M1V1 = M2V2

100 × 0.1 = M2 × 1

M2 = 10M / ml

Similarly, for [Acid]

1000 μl = 1ml

1 M / ml

ph = pka + log [salt]/[acid]

= 4.76 + log [10]/[1]

= 4.76 + log 10

= 4.76 + 1

= 5.76

Therefore, pH = 5.76

Alt. concept

If [salt] > [acid] = pH > pKa

[salt] < [acid] = pH < pKa

[salt] = [acid] = pH = pKa