Question

The pH at the midpoint in the titration of an acid with a base is A) equal to the pK of the corresponding base. B) equal to the pK of the corresponding acid. C) equal to 14 minus the pK of the corresponding acid. D) equal to 14 plus the pK of the corresponding base. E) none of the above

Answer 1

Answer:

The pH at the midpoint in the titration of an acid with a base is

A) equal to the pK of the corresponding base.

B) equal to the pK of the corresponding acid.

C) equal to 14 minus the pK of the corresponding acid.

D) equal to 14 plus the pK of the corresponding base.

E) none of the above

Explanation:

When a weak acid is titrated with a strong base, then a buffer solution is formed.

pH of a buffer solution can be calculated by using the formula:

$pH=pKa+log\frac{[salt]}{[acid]}$

Exactly at the mid point,

[conjugate base of the salt]=[acid]

So, log [salt]/[acid] =0

Hence, pH of the solution will be equal to pKa of the weak acid.

Answer is option B.