A weak acid HX has the dissociation constant 1 × 10-5 M. It forms a salt NaX on reaction with alkali. The percentage hydrolysis of 0.1 M solutions of NaX is

Question

A weak acid HX has the dissociation constant 1 × 10-5 M. It forms a salt NaX on reaction with alkali. The percentage hydrolysis of 0.1 M solutions of NaX is (A) 0.0001 % (B) 0.01 % (C) 0.1 % (D) 0.15 %

Tardigrade Admin · Accepted Answer

NaX: Salt of weak acid, strong base ⇒ α=√(Kh/C)=√(Kw/Ka ⋅ C)=√(10-14/10-5 × 0.1)=10-4 ⇒ % hydrolysis =0.01 % (Check that approximation is valid)

Q. A weak acid $H X$ has the dissociation constant $1 \times 1 0^{- 5} M$ . It forms a salt $N a X$ on reaction with alkali. The percentage hydrolysis of $0.1 M$ solutions of $N a X$ is

$0.0001%$

$0.01%$

$0.1%$

$0.15%$

$N a X$ : Salt of weak acid, strong base
$\Rightarrow α = \frac{K _{h}}{C} = \frac{K _{w}}{K _{a \cdot C}} = \frac{1 0 ^{- 14}}{1 0 ^{- 5} \times 0.1} = 1 0^{- 4}$
$\Rightarrow %$ hydrolysis $= 0.01%$
(Check that approximation is valid)

Q. A weak acid HX has the dissociation constant 1×10−5M. It forms a salt NaX on reaction with alkali. The percentage hydrolysis of 0.1M solutions of NaX is

0.0001%

0.01%

0.1%

0.15%