Q. A buffer solution is prepared by mixing equal concentration of acid (ionisation constant $K_{a}$) and a salt. The pH of buffer is
A) $pK_{a} + 7$
B) $14 - pK_{a}$
C) $pK_{a}$
D) $pK_{a} + 1\$
Explanation
(c)
For buffer solution,
$pH = pK_{a} + \log\frac{\lbrack salt\rbrack}{\lbrack base\rbrack}$
If concentration of salt = concentration of acid
$i.e$., $\lbrack salt\rbrack = \lbrack acid\rbrack$
Hence, $pH = pK_{a}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.