MCQ
$0.01\,\,M\,HA\,(aq.)$ is  $2\%$  ionized $; [OH^-]$  of solution is
  • A
    $2 \times 10^{-4}$
  • B
    $ 10^{-8}$
  • $5 \times 10^{-11}$
  • D
    $5 \times 10^{-12}$

Answer

Correct option: C.
$5 \times 10^{-11}$
c
$\mathrm{HA}_{(\mathrm{aq})} \rightleftharpoons \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{A}_{(\mathrm{aq})}^{-}$

$\Rightarrow \frac{\left[\mathrm{H}^{+}\right]}{[\mathrm{HA}]} \times 100=2$

$\Rightarrow \frac{\left[\mathrm{H}^{+}\right]}{0.01} \times 100=2$

$\Rightarrow\left[\mathrm{H}^{+}\right]=\frac{0.02}{100}=2 \times 10^{-4} \mathrm{M}$

$\therefore\left[\mathrm{OH}^{-}\right]=\frac{10^{-14}}{2 \times 10^{-4}}=0.5 \times 10^{-10} \mathrm{m}$

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