Question

What is the order of relative basic strength of $Cl{O}_2^{-},Cl{O}_3^{-},Cl{O}_4^{-}?$

• A. $Cl{O}_2^{-}>Cl{O}_3^{-}>Cl{O}_4^{-}$
• B. $Cl{O}_3^{-}>Cl{O}_2^{-}>Cl{O}_4^{-}$
• C. $Cl{O}_4^{-}>Cl{O}_2^{-}>Cl{O}_3^{-}$
• D. $Cl{O}_2^{-}>Cl{O}_4^{-}>Cl{O}_3^{-}$

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 $Cl{O}_2^{-}\to x-4=-1$

$x=+3$

$Cl$ in $Cl{O}_3^{-}\to x-6=-1$

$x=+5$

$Cl$ in $Cl{O}_4^{-}\to x-8=-1$

$x=+7$

Thus, order of acidic nature is

$Cl{O}_4^{-}>Cl{O}_3^{-}>Cl{O}_2^{-}$

and order for basic strength is

$Cl{O}_2^{-}>Cl{O}_3^{-}>Cl{O}_4^{-}$

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.

$\because Cl{O}_2^{-}$ has only two oxygen atoms while $Cl{O}_4^{-}$ has four oxygen atoms. Thus, order of basic strength is

$Cl{O}_2^{-}>Cl{O}_3^{-}>Cl{O}_4^{-}$