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)

$HO\stackrel{+1}{\mathrm{Cl}}<H\stackrel{+3}{\mathrm{Cl}}{O}_2<H\stackrel{+5}{\mathrm{Cl}}{O}_3<H\stackrel{+7}{\mathrm{Cl}}{O}_4$

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.