Q. At a certain temperature, the dissociation constants of formic acid and acetic acid are $1.8 \times 10^{- 4}\ and\ 1.8 \times 10^{- 5}$ respectively. The concentration of acetic acid solution in which the hydrogen ion has the same concentration as in 0.001 M formic acid solution is equal to
A) 0.01 M
B) 0.001 M
C) 0.1 M
D) 0.0001 M
Explanation
(a)
$\left\lbrack H^{+} \right\rbrack = K_{a}.C$
Given, $\left\lbrack H^{+} \right\rbrack_{HCOOH} = \left\lbrack H^{+} \right\rbrack_{CH_{3}COOH}$
$K_{a}.C = K_{a}^{'}C'$
$\Rightarrow \ \ 1.8 \times 10^{- 4} \times 0.001 = 1.8 \times 10^{- 5} \times C'$
$\therefore\ \ \ C^{'} = 0.01M$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.