Q. A weak acid $HX$ has dissociation constant $10^{- 5}$. The pH of 0.1 M solution of this acid will be
A) 2
B) 3
C) 4
D) 5
Explanation
(b)
$\left\lbrack H^{+} \right\rbrack = \sqrt{K_{a} \times C}$
$= \sqrt{10^{- 5} \times 0.1}$
$= \ \sqrt{10^{- 6}} = 10^{- 3}\$
pH$= - \log{\left\lbrack H^{+} \right\rbrack = - \log{10^{- 3} = 3}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.