. Which of the following is a Lewis acid

A. PH3

B. B(CH3)3

C. NaH

D. NF3

Best Answer

Ans: B

Sol: ||| Lewis Acid accepts pairs of electrons whereas Lewis base donates pairs of electrons. 

B(CH3)3 is a 6 e- species - which means that the central atom has an incomplete octet. It is an electron deficient molecule and thus can accept electrons. Hence, it is considered to be a Lewis Acid

In the case of PH3 P has a lone pair and thus P can donate. Hence, it is considered to be Lewis base. 
NaH: Na can donate lone pair, thus acting as Lewis base. 


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