Equilibrium Ques 61
61. 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 equilbrium is closest to
[2007]
(a) $1.00 \%$
(b) $99.9 \%$
(c) $0.100 \%$
(d) $99.0 \%$
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Answer:
Correct Answer: 61.(a)
Solution:
- (a) Given $K_a=1.00 \times 10^{-5}, C=0.100 $ $mol$ for a weak electrolyte,
degree of dissociation
$\alpha=\sqrt{\frac{K_a}{C}} \sqrt{\frac{1 \times 10^{-5}}{0.100}}=10^{-2}=1 \%$
BETA
