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Question: Answered & Verified by Expert
Accumulation of lactic acid $\left(\mathrm{HC}_3 \mathrm{H}_5 \mathrm{O}_3\right)$, a monobasic acid in tissues leads to pain and a feeling of fatigue. In a 0.10
$\mathrm{M}$ aqueous solution, lactic acid is $3.7 \%$ dissociates. The value of dissociation constant, $\mathrm{K}_a$, for this acid will be:
ChemistryIonic EquilibriumNEETNEET 2013 (Karnataka)
Options:
  • A $1.4 \times 10^{-5}$
  • B $1.4 \times 10^{-4}$
  • C $3.7 \times 10^{-4}$
  • D $2.8 \times 10^{-4}$
Solution:
2207 Upvotes Verified Answer
The correct answer is: $1.4 \times 10^{-4}$
$$
\alpha=\frac{3.7}{100}=0.037
$$
According to Ostwald's formula
$$
\begin{aligned}
\mathrm{K}_\alpha & =\alpha^2 \mathrm{C} \\
& =(0.037)^2 \times 0.10 \\
& =1.369 \times 10^{-4}
\end{aligned}
$$

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