MCQ
A weak acid $HA$ has a $K_a$ of $1.00 \times 10^{-5} $. If $0.100\,mol$ of this acid is dissolved in one litre of water the percentage of acid dissociated at equilibrium is closest to.....$\%$
  • A
    $0.100$
  • B
    $99$
  • $1$
  • D
    $99.9$

Answer

Correct option: C.
$1$
c
$\mathrm{K}_{\mathrm{a}}=\mathrm{C} \alpha^{2}$

$\Rightarrow 10^{-5}=0.1 \times \alpha^{2}$

$\Rightarrow 10^{-2}=\alpha$

$\Rightarrow 1 \%=\alpha$

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