Question

Which anion is the weakest base?

• A. $C _{2} H _{5} O ^{-}$
• B. $NO _{3}^{-}$
• C. $F ^{-}$
• D. $CH _{3} COO ^{-}$

Answer 1

Answer: (B)

$NO _{3}^{-}$

Answer 2

Conjugated base of a stronger acid is weak. The corresponding acids of the given conjugated bases are as (in order of acidity) $C _{2} H _{5} OH < CH _{3} COOH < HF < HNO _{3}$ $\therefore$ The order of basicity is $C _{2} H _{5} O ^{-} > CH _{3} COO > F ^{-} > NO _{3}^{-}$ Thus, $NO _{3}^{-}$is the weakest base among the given.