Question

Identify the pair containing only Lewis acids

• A. BF\(_3\), NH\(_3\)
• B. H\(^+\), BF\(_3\)
• C. F\(^-\), H\(_2\)O
• D. NH\(_4^+\), NH\(_3\)

Hint:

To quickly identify Lewis acids, look for three main categories: 1. Positive ions (like \(H^+\), \(Mg^{2+}\)). 2. Molecules with an incomplete octet on the central atom (like \(BF_3\), \(AlCl_3\)). 3. Molecules with a central atom that can accommodate more than an octet and is bonded to electronegative atoms (like \(SiF_4\), \(PCl_5\)).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Identify pair where both are Lewis acids (electron pair acceptors).

Step 2: Key Concept (Alternate):
Lewis acids: electron deficient species (H⁺, BF₃, AlCl₃). Lewis bases: lone pair donors (NH₃, F⁻, H₂O).

Step 3: Detailed Explanation:
H⁺(empty 1s), BF₃(incomplete octet on B) both accept electrons. Others have bases.

Step 4: Final Answer:
H⁺, BF₃ are both Lewis acids.