Values of dissociation constant, Kₐ are given as follows Acid &

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6-2.Equilibrium-II (Ionic Equilibrium)

hard

Values of dissociation constant, $K_a$ are given as follows

Acid $K_a$

$HCN$ $6.2\times 10^{-10}$

$HF$ $7.2\times 10^{-4}$

$HNO_2$ $4.0\times 10^{-4}$

Correct order of increasing base strength of the base $CN^-,F^-$ and $NO_2^-$ will be

$F^- < CN^- < NO_2^-$

$NO_2^- < CN^- < F^-$

$F^- < NO_2^- < CN^-$

$NO_2^- < F^- < CN^-$

(JEE MAIN-2013)

Solution

Higher the value of $K_a$ lower will be the value of $pK_a$ $i.e.$ higher will be the acidic nature. Further since $CN^-, F^-$ and $NO_2^-$ are conjugate base of the acids $HCN, HF$ and $HNO_2$ respectively hence the correct order of base strength will be $F^- < NO_2^- < CN^-$ ( $\because $ stronger the acid weaker will be its conjugate base)

Standard 11

Chemistry

$HClO$ is a weak acid. The concentration of ${H^ + }$ ions in $0.1\,M$ solution of $HClO\,({K_a} = 5 \times {10^{ – 8}})$ will be equal to

medium

Derive the equation of ionization constant $({K_b})$ of weak base.

normal

What concentration of $Ac^-$ ions will reduce $H_3O^+$ ion to $2 × 10^{-4}\ M$ in $0.40\ M$ solution of $HAc$ ? $K_a (HAc) = 1.8 × 10^{-5}$ ?

hard

The $pH$ of a $0.1\ M$ aqueous solution of a very weak acid $(HA)$ is $3$. What is its degree of dissociation ?……$\%$

medium

$5\%$ ionization is occur in $0.01$ $M$ $C{H_3}COOH$ solution. Calculate its dissociation constant.