Question

Which of the following are Lewis acids ?

• A. $PH_3$ and $BCl_3$
• B. $AlCl_3$ and $SiCl_4$
• C. $PH_3$ and $SiCl_4$
• D. $BCl_3$ and $AlCl_3$

Answer 1

Answer: (D)

$BCl_3$ and $AlCl_3$

Answer 2

$BCl _{3}-$ electron deficient, incomplete octet

$AlCl _{3}-$ electron deficient, incomplete octet

Ans-(4) $BCl _{3}$ and $AlCl _{3}$
$SiCl _{4}$ can accept lone pair of electron in $d$ -orbital of silicon hence it can act as Lewis acid.

Although the most suitable answer is $(4)$.

However, both option $(4) \& (2)$ can be considered as correct answers.

e.g. hydrolysis of $SiCl _{4}$