1. Tardigrade
  2. Question
  3. Chemistry
  4. Values of dissociation constant, Ka are given as follows: Acid Ka HCN 6.2 × 10-10 HF 7.2 × 10-4 HNO2 4.0 × 10-4 Correct order of increasing base strength of the base CN- F- and NO2- will be :

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Q. 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 :

JEE MainJEE Main 2013Equilibrium

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
$F^- < NO_2^-< CN^-$
($\therefore $ stronger the acid weaker will be its conjugate base)