The pH of a buffer solution will be equal to the p Ka of acid, only if

Question

The pH of a buffer solution will be equal to the p Ka of acid, only if (A) molar concentration of acid is greater than molar concentration of conjugate base. (B) molar concentration of acid is smaller than molar concentration of conjugate base. (C) molar concentration of acid is equal to the molar concentration of conjugate base. (D) molar concentration of acid is almost negligible.

Tardigrade Admin · Accepted Answer

Handerson - Hasselbalch equation for acidic buffer solution is given as,

p H = p K_{a} + lo g \frac{[Conjugate base ]}{[ Acid ]}

Therefore, if the molar concentration of acid is equal to the molar concentration of conjugate base, we have

p H = p K_{a} + lo g 1

Or

p H = p K_{a} [∵ lo g 1 = 0]

Hence,

p H

of a buffer solution becomes equal to

p K_{a}

of acid only if,
[Acid

] = [

Conjugate base

]

Q. The pH of a buffer solution will be equal to the pKa​ of acid, only if

molar concentration of acid is greater than molar concentration of conjugate base.

molar concentration of acid is smaller than molar concentration of conjugate base.

molar concentration of acid is equal to the molar concentration of conjugate base.

molar concentration of acid is almost negligible.

Q. The $p H$ of a buffer solution will be equal to the $p K_{a}$ of acid, only if