Question

The compound that is not a Lewis acid is:

• A. $B{F}_3$
• B. $AlC{l}_3$
• C. $BeC{l}_2$
• D. $N{H}_3$

Answer 1

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

Lewis Concept (Electronic concept) :
Lewis acid - species which can accept an electron pair with the formation of a coordinate bond.
Lewis base - species which has a lone pair of electrons available for donation.
$N{H}_3$ already has a lone pair on nitrogen so it cannot accept a lone pair of electrons thus it does not act as a lewis acid .
It can donate a lone pair of electon to form a Lewis base.