Question

What is the order of relative basic strength of $ClO _{2}^{-}, ClO _{3}^{-}, ClO _{4}^{-} ?$

• A. $ClO _{2}^{-}> ClO _{3}^{-}> ClO _{4}^{-}$
• B. $ClO _{3}^{-}> ClO _{2}^{-}> ClO _{4}^{-}$
• C. $ClO _{4}^{-}> ClO _{2}^{-}> ClO _{3}^{-}$
• D. $ClO _{2}^{-}> ClO _{4}^{-}> ClO _{3}^{-}$

Answer 1

Answer: (A)

More be the oxidation state of central atom (i.e. $Cl$ -atom), more is the acidic nature of the species and lesser will be the basic strength.

As, oxidation number of :

$Cl$ in $ClO _{2}^{-} \rightarrow x-4=-1$

$x=+3$

$Cl$ in $ClO _{3}^{-} \rightarrow x-6=-1$

$x =+5 $

$C l $ in $ClO _{4}^{-} \rightarrow x-8 =-1 $

$x =+7$

Thus, order of acidic nature is

$ClO _{4}^{-}> ClO _{3}^{-}> ClO _{2}^{-}$

and order for basic strength is

$ClO _{2}^{-}> ClO _{3}^{-}> ClO _{4}^{-}$

Alternate method

The more be the oxygen atom in the given species, the more is the dispersion of electrons from $Cl$ -atoms, which decreases the basic strength.

$\because ClO _{2}^{-}$ has only two oxygen atoms while $ClO _{4}^{-}$ has four oxygen atoms. Thus, order of basic strength is

$ ClO _{2}^{-}> ClO _{3}^{-}> ClO _{4}^{-}$