Q. What will be the pH and % $\alpha$ respectively for the salt $BA$ of 0.1 M concentration? Given, $K_{a}$ for $HA = 10^{- 6}$ and $K_{b}$ for $BOH = 10^{- 6}$
A) $7,\ 10\%$
B) $5,\ 10\%$
C) 5, 0.1%
D) 7, 1%
Explanation
(a)
$\because pH = \frac{1}{2}pK_{w} + \frac{1}{2}pK_{a} - \frac{1}{2}pK_{b}$
$= \frac{1}{2} \times 14 + \frac{1}{2} \times 6 - \frac{1}{2} \times 6$
$pH = 7$
$\alpha = \sqrt{\frac{K_{w}}{K_{a} \times K_{b}}} = \sqrt{\frac{10^{- 14}}{10^{- 6} \times 10^{- 6}}} = \sqrt{10^{- 2}}$
$= 10^{- 1} = 0.1or\ 10\%$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.