The dissociation constant of weak monobasic acid is $2.7 \times 10^{-5}$. If degree of dissociation of acid…

The dissociation constant of weak monobasic acid is $2.7 \times 10^{-5}$. If degree of dissociation of acid is $3 \times 10^{-2}$, what is the concentration of acid?
  1. 0.24 M
  2. 0.03 M
  3. 0.3 M
  4. 0.11 M

Solution

weak monobasic acid (HA) \(\mathrm{HA}_{(\mathrm{aq})} \rightleftharpoons \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{A}_{(\mathrm{aq})}^{-}\) \(t=0 \quad C\) teq, \(\mathrm{C}-\mathrm{C} \propto \quad \mathrm{C} \propto \quad \mathrm{C} \propto\) \(\begin{aligned} & \mathrm{K}_{\mathrm{a}}=\frac{\left[\mathrm{H}^{+}\right]\left[\mathrm{A}^{-}\right]}{[\mathrm{HA}]}=\frac{\mathrm{C} \propto^2}{1-\propto}(1-\propto \simeq 1) \\ & \mathrm{K}_{\mathrm{a}}=\mathrm{C} \propto^2 \\ & \mathrm{C}=\frac{\mathrm{Ka}}{\propto^2}=\frac{2.7 \times 10^{-5}}{\left(3 \times 10^{-2}\right)^2}=0.03 \mathrm{M} \end{aligned}\)

Asked in: MHT CET 2021 (22 Sep Shift 1)

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