Equilibrium - Result Question 60
####62. Accumulation of lactic acid $(HC_3 H_5 O_3)$, a monobasic acid in tissues leads to pain and a feeling of fatigue. In a $0.10 M$ aqueous solution, lactic acid is $3.7 %$ dissociated. The value of dissociation constant, $K_a$, for this acid will be:
(a) $2.8 \times 10^{-4}$
(b) $1.4 \times 10^{-5}$
(c) $1.4 \times 10^{-4}$
(d) $3.7 \times 10^{-4}$
[NEET Kar. 2013]
Show Answer
Solution:
(c) $\alpha=\sqrt{\frac{K_a}{c}}=0.037=\sqrt{\frac{K_a}{0.10}}$;
$ \begin{aligned} K_a & =(0.037)^{2} \times 0.10=1.37 \times 10^{-4} \\ & \simeq 1.4 \times 10^{-4} \end{aligned} $
