Chemistry · General Organic Chemistry

NEET (UG) 2023 — Question 63

Amongst the given options, which of the following molecules/ions acts as a Lewis acid?

Option A:
$\mathrm{H}_{2} \mathrm{O}$
Option B:
$\mathrm{BF}_{3}$
Correct
Option C:
$\ce{OH-}$
Option D:
$\mathrm{NH}_{3}$

Answer: B

Step-by-step solution

Lewis acid is an electron-pair acceptor; it must possess a vacant orbital to accept a lone pair. In $\ce{BF3}$ , boron has only six valence electrons and an empty 2p orbital, so it can accept a lone pair. $\ce{H2O}$ has lone pairs on oxygen and donates an electron pair, so it acts as a Lewis base. $\ce{OH-}$ has lone pairs and donates an electron pair, so it acts as a Lewis base. $\ce{NH3}$ has a lone pair on nitrogen and donates it, so it acts as a Lewis base. Therefore, among the given options, the Lewis acid is $\ce{BF3}$ . Correct option: B.

Answer key and solution verified before publishing.

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Exam: NEET (UG) 2023
Paper: 2023 paper
Subject: Chemistry
Chapter: General Organic Chemistry
Topic: Types of Electronic Effects