Question

Which one of the following represents the correct order of acidic strength?

• A. $\text{HOClO} \, \text{ < } \, \text{HOCl < } \, \text{HOClO}_{3} \text{ < HOClO}_{2}$
• B. $\text{HOClO}_{2} < \text{HOClO}_{3} < \text{HOCIO} < \text{HOCl}$
• C. $\text{HOClO}_{3} < \text{HOClO}_{2} < \text{HOClO} < \text{HOCl}$
• D. $\text{HOCl} < \text{HOCIO} < \text{HOClO}_{2} < \text{HOClO}_{3}$

Answer 1

Answer: (D)

$HO\overset{+ 1}{C l} < H\overset{+ 3}{C l}O_{2} < H\overset{+ 5}{C l}O_{3} < H\overset{+ 7}{C l}O_{4}$

As the number of oxygen atom increases, an increasing amount of electron density shifts from Cl atom to more electronegative O atom. Hence as the oxidation number of Cl atom increases, the amount of actual positive charge on Cl atom increases which in turn attracts the electron density from $O-H$ bond, hence the $O-H$ bond is weakened and proton is easily released and acidity increases.