Question

Which of the following species is not a Lewis acid?

• A. $B{F}_3$
• B. $C{u}^{2+}$
• C. $N{H}_3$
• D. $AlC{l}_3$

Answer 1

The correct option is C $N{H}_3$

Species which can accept a pair of electrons from another species.
$N{H}_3$ can donate a pair of electrons while $C{u}^{2+}$, $AlC{l}_3$, $B{F}_3$ can accept lone pair of electron since they have vacant orbitals.
hence, $N{H}_3$ is a lewis-base while remaining species are lewis-acid.