For a weak acid HA with dissociation constant {10^{ - 9}},,,pOH of its 0.1 ,M solution is

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6-2.Equilibrium-II (Ionic Equilibrium)

medium

For a weak acid $HA$ with dissociation constant ${10^{ - 9}},\,\,pOH$ of its $0.1 \,M$ solution is

A

$10$

B

$3$

C

$11$

D

$9$

(AIPMT-1989)

Solution

(d) Dissociation constant of $HA = {10^{ – 9}}$

$HA⇌{H^ + } + {A^ – }$

$[{H^ + }] = \sqrt {\frac{{{K_a}}}{C}} $ $ = \sqrt {\frac{{{{10}^{ – 9}}}}{{0.1}}} $ ; $[{H^ + }] = {10^{ – 5}}$

$\therefore \,pH = 5$

$pH+pOH = 14$

$pOH = 14 – pH$$ = 14 – 5$ ; $pOH = 9$

Standard 11

Chemistry

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