QJEEM18Ch1f1f: JEE Main 2018 Chemistry - Class 11 JEEM18Ch1f1f Solution: Which of the following are Lewis acids?

The compound which have the ability to accepted at least are lone pair electron.

Structure of BCl₃ is



Here B is electron deficient atom, so it can accepted lone pair. So it is a lewis acid.

Structure of AlCl₃



Here, Al also a electron deficient atom so it has vacant orbital and in that vacant orbital it can take lone pair. So it is also lewis acid.



Here in PH₃ there is vacant 3d orbital but it Can't take. Lone pair in 3d orbital because P is more electro-negative than H so around P atom negative charge density is created and tendency of accepting electron decreases. So PH₃ is not lewis acid.



Here octet of Si full ut in has a tendency of accepting lone pair in vacant 3d orbital.

This can be shown by following reaction.



So, here option (A) and (C) both are correct. But as SiCl₄ is not as strong lewis acid as BCl₃ and AlCl₃, So we can say option (A) is more correct.