The equilibrium constant for :

${\text{CN}}^{-}+{\text{CH}}_3\text{COOH}\rightleftharpoons \text{HCN}+{\text{CH}}_3{\text{COO}}^{-}$ Is :

(Given ${\text{p}}_{{\text{K}}_{\text{b}}}$ for ${\text{CN}}^{-}=\text{4.69}$ and ${\text{p}}_{{\text{K}}_{\text{b}}}$ for ${\text{CH}}_3{\text{COO}}^{-}=\text{9.25}$ )

$0.01$ moles of a weak acid $\mathrm{HA} \left({\mathrm{K}}_{\mathrm{a}}=2.0\times {10}^{-6}\right)$ is dissolved in $1.0 \mathrm{L}$ of $0.1\mathrm{M} \mathrm{HCl}$ solution. The degree of dissociation of $\mathrm{HA}$ is __________ $\times {10}^{-5}$ (Round off to the Nearest Integer). [Neglect volume change on adding $\mathrm{HA}$ and assume degree of dissociation $<<1$]

Given below are two statements: one is labelled as Assertion $\mathrm{A}$ and the other is labelled as Reason $\mathrm{R}$.

Assertion $\mathrm{A}$ :Phenolphthalein is a $\mathrm{pH}$ dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium

Reason $\mathrm{R}$ : Phenolphthalein is a weak acid. It doesn't dissociate in basic medium.

In the light of the above statements, choose the most appropriate answer from the options given below

The degree of dissociation of $0.1\mathrm{mol} {\mathrm{L}}^{-1}$acetic acid in water is

( $\mathrm{K}$ of acetic acid is ${10}^{-5}$ )