Q. The $pK_{b}$ value of $NH_{3}$ is 5. Calculate the pH of the buffer solution, 1 L of which contains 0.01 M $NH_{4}Cl\ and\ 0.10\ M\ NH_{4}OH$
A) 4
B) 6
C) 8
D) 10
Explanation
(d)
$pOH = K_{b} + \log\frac{\lbrack salt\rbrack}{\lbrack base\rbrack}$
given, $pK_{b} = 5,\ \lbrack Base\rbrack = 0.10\ M,$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \lbrack salt\rbrack = 0.01\ M$
$\therefore$ $pOH = 5 + \log{\frac{0.01}{0.10} = 4}$
$pH + pOH = 14$
$\therefore$ $pH = 14 - 4 = 10$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.