Question

Which one of the following species is not a base according to any acid-base theory?

• A. $Ca(OH{)}_2$
• B. $N{H}_3$
• C. $HS{O}_4^{-}$
• D. $B{F}_3$

Answer 1

The correct option is D $B{F}_3$

Option (a) - $Ca(OH{)}_2$. is a base as it releases $O{H}^{-}$ ions in its aqueous solution => Arrhenius Base
Option(b) - $N{H}_3$ is a proton acceptor => Bronsted-Lowry Base
Option(c) - $HS{O}_4^{-}$ is the conjugate base of $H_{2}S{O}_4$ => Bronsted-Lowry Base
Option(d) - $B{F}_3$ has no free electrons or $O{H}^{-}$ to release; rather it has vacant orbitals (2p) which attract electrons. Hence, it behaves as a Lewis acid.