Calculate the concentration of weak monobasic acid if its degree of dissociation and dissociation constant…

Calculate the concentration of weak monobasic acid if its degree of dissociation and dissociation constant are $5.0 \times 10^{-4}$ and $5.0 \times 10^{-9}$ respectively.
  1. 0.1 M
  2. $\quad 0.02 \mathrm{M}$
  3. $\quad 0.03 \mathrm{M}$
  4. $\quad 0.04 \mathrm{M}$

Solution

For a weak monobasic acid, $\begin{aligned} & \mathrm{K}_{\mathrm{a}}=\alpha^2 \mathrm{c} \\ \therefore \quad & \mathrm{c}=\frac{\mathrm{K}_{\mathrm{a}}}{\alpha^2}=\frac{5.0 \times 10^{-9}}{\left(5.0 \times 10^{-4}\right)^2}=\frac{1 \times 10^{-9}}{5 \times 10^{-8}}=0.02 \mathrm{M} \end{aligned}$

Asked in: MHT CET 2024 (04 May Shift 1)

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