Q25 / 90 · KVPY 2016 (SB/SX) · Chemistry
The $\mathrm{pK}_{\mathrm{a}}$ of oxoacids of chlorine in water follows the order
- A$\mathrm{HClO} < \mathrm{HClO}_{3} < \mathrm{HClO}_{2} < \mathrm{HClO}_{4}$
- Correct answerB$\mathrm{HClO}_{4} < \mathrm{HClO}_{3} < \mathrm{HClO}_{2} < \mathrm{HClO}$
- C$\mathrm{HClO}_{4} < \mathrm{HClO}_{2} < \mathrm{HClO}_{3} < \mathrm{HClO}$
- D$\mathrm{HClO}_{2} < \mathrm{HClO} < \mathrm{HClO}_{3} < \mathrm{HClO}_{4}$
Solution
Acidic strength of acid is
$$
\begin{array}{l}
\mathrm{HClO}_{4}>\mathrm{HClO}_{3}>\mathrm{HClO}_{2}>\mathrm{HClO} \\
{\left[\mathrm{H}^{+}\right] \uparrow \mathrm{ka} \uparrow \mathrm{p}^{\mathrm{ka}} \downarrow} \\
\therefore \mathrm{p}^{\mathrm{k}_{\mathrm{a}}} \text { order } \mathrm{HClO}_{4} < \mathrm{HClO}_{3} < \mathrm{HClO}_{2} < \mathrm{HClO}
\end{array}
$$
Hence, the correct answer is option: 'B'.