Question

Which one of the following molecular hydrides acts as a Lewis acid?

• A. \( {NH}_3 \)
• B. \( {H}_2{O} \)
• C. \( {B}_2{H}_6 \)
• D. \( {CH}_4 \)

Hint:

A Lewis acid accepts an electron pair, while a Lewis base donates an electron pair. Boron compounds like \( {B}_2{H}_6 \) are known to act as Lewis acids due to their electron deficiency.

Answer 1

The Correct Option is C

A Lewis acid is a substance that can accept a pair of electrons. In the case of molecular hydrides: 
- \( {NH}_3 \) (Ammonia) is a Lewis base because it has a lone pair of electrons on nitrogen that can be donated. 
- \( {H}_2{O} \) (Water) is also a Lewis base due to the lone pairs on oxygen. 
- \( {B}_2{H}_6 \) (Diborane) acts as a Lewis acid because boron atoms in diborane have an incomplete octet and can accept electron pairs. 
- \( {CH}_4 \) (Methane) does not act as a Lewis acid because it does not have an empty orbital to accept electron pairs. 
Thus, \( {B}_2{H}_6 \) (Diborane) is the only hydride that acts as a Lewis acid.