Question

Strongest conjugate base is

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

Answer 1

Answer: (A)

If acid is weak, its conjugate base is strong. Greater the oxidation number of $Cl$, stronger the acid and thus, weaker the conjugate base.

Oxidation number of $Cl$ and acid strength increases
$\stackrel{Cl{O}^{-}Cl{O}_2^{-}Cl{O}_3^{-}Cl{O}_4^{-}}{\leftarrow }$
Conjugate base strength increases.
Hence, $Cl{O}^{-}$is the strongest base.