Question

Which of the following is lewis acid?

• A. $N{H}_3$
• B. $AlC{l}_3$
• C. $P{H}_3$
• D. None of the above

Answer 1

The correct option is B $AlC{l}_3$

Species which can accept a pair of electrons from another species is called as Lewis acid.
$AlC{l}_3$ has vacant p orbital and thus it can accept a pair of electrons and hence is lewis acid.
$N{H}_3,P{H}_3$ are Lewis bases.