Q5 / 180 · KCET 2021 · Chemistry
$K_{a}$ values for acids $\mathrm{H}_{2} \mathrm{SO}_{3}, \mathrm{HNO}_{2}, \mathrm{CH}_{3} \mathrm{COOH}$ and $\mathrm{HCN}$ are respectively $1.3 \times 10^{-2}$, $4 \times 10^{-4}, 1.8 \times 10^{-5}$ and $4 \times 10^{-10}$, which of the above acids produces stronger conjugate base in aqueous solution?
- A$\mathrm{H}_{2} \mathrm{SO}_{3}$
- B$\mathrm{HNO}_{2}$
- C$\mathrm{CH}_{3} \mathrm{COOH}$
- Correct answerD$\mathrm{HCN}$
Solution
Lower the value of $K_{a}$, lower will be the acidic strength and stronger will be the conjugate base. Therefore, among the given acids, HCN has the lowest $K_{a}$ value (i.e. $4 \times 10^{-10}$ ).
Hence, it is the strongest conjugate base.
Hence, the correct answer is option: 'D'.