Question

Which of the following will qualify as a Lewis acid?

• A. $NaF$
• B. $NaCl$
• C. ${BF}_3$
• D. $Mg{Cl}_2$

Answer 1

Answer: (C), (D)

The correct options are
C ${BF}_3$
D $Mg{Cl}_2$

According to Lewis concept of acids and bases, an acid is a substance which can accept a lone pair of electrons whereas a base is a substance which can donate a lone pair of electrons.

Molecules having central atom with incomplete octet e.g. $B{F}_3,AlC{l}_3,MgC{l}_2$ etc. These molecules will readily accept a lone pair of electrons to complete their octet and hence will qualify as Lewis acids.