JEE Main 2021 · ChemistryMultiple choiceSingle correctEasyConceptual

JEE Main 27 August 2021, Shift 1, Chemistry Q35

Question 35 of 90 in this shift, Chemistry question 5 of 30, Section A.

In which one of the following molecules strongest back donation of an electron pair from halide to boron is expected ?

(1) $\mathrm{BI_3}$
(2) $\mathrm{BBr_3}$
(3) $\mathrm{BCl_3}$
(4) $\mathrm{BF_3}$ Official answer

Official answer

Option 4

NTA final key.

Chapter: The p-Block Elements
Topic: Group 13 & 14
Idea tested: Back-Bonding and Lewis Acidity in Boron Trihalides

Same topic in other shifts

All Group 13 & 14 questions

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4 Apr 2025, Shift 2 · Q57The elements of Group 13 with highest and lowest first ionisation enthalpies are respectively :EasySingle correct
4 Apr 2025, Shift 2 · Q58Given below are two statements : Statement (I) : The first ionisation enthalpy of group 14 elements is higher than the corresponding…MediumTwo statements

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.