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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumRecall

JEE Main 25 July 2021, Shift 1, Chemistry Q35

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

At 298.2 K the relationship between enthalpy of bond dissociation (in kJ mol−1^{-1}) for hydrogen (EH\mathrm{E_H}) and its isotope, deuterium (ED\mathrm{E_D}), is best described by :
  1. (1)EH=ED\mathrm{E_H=E_D}
  2. (2)EH≃ED−7.5\mathrm{E_H\simeq E_D-7.5}Official answer
  3. (3)EH=2ED\mathrm{E_H=2E_D}
  4. (4)EH=12ED\mathrm{E_H=\frac{1}{2}E_D}

Official answer

Option 2

NTA final key.

Chapter
Hydrogen
Topic
Hydrogen and Hydrides
Idea tested
H-H Bond Dissociation Enthalpy

Same idea in other shifts

Asked 3× in all
  1. 4 Aug 2021, Shift 1 · Q37Naturally occurring hydrogen contains three isotopes, protium (H), deuterium (D) and tritium (T). What is correct order of heat of…EasySingle correct
  2. 31 Aug 2021, Shift 2 · Q34Which one of the following statements is incorrect ?MediumSingle correct

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.