Question

Which one is a Lewis acid?

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

Hint:

Lewis acids are electron-pair acceptors. Compounds like B\(_2\)H\(_6\) with electron-deficient atoms, such as boron, can accept electrons, making them Lewis acids.

Answer 1

The Correct Option is B

Step 1: Lewis Acid Definition
A Lewis acid accepts an electron pair, unlike a Brønsted-Lowry acid, which donates a proton. Lewis acids usually have an empty orbital or can accept electrons.
Step 2: Option Analysis

• CH₄ (Methane): Not a Lewis acid; it's electron-rich and lacks an orbital to accept electrons.
• B₂H₆ (Diborane): A Lewis acid. Its boron atoms are electron-deficient and can accept electron pairs.
• H₂O (Water): Not a Lewis acid; it can donate electron pairs (a Lewis base) but lacks an orbital to accept them.
• NH₃ (Ammonia): Not a Lewis acid; it has a lone pair and acts as a Lewis base.

Step 3: Conclusion
The correct answer is B₂H₆, a Lewis acid because its electron-deficient boron atoms accept electron pairs.
Conclusion:

B₂H₆ is a Lewis acid.