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Saturday, 31 October

JEE Main · Chemistry · Thermodynamics (Chemistry)

Bond Enthalpy Calculations

JEE Main asked Bond Enthalpy Calculations 5 times in 5 of the 108 shifts Lumi analysed, in 2021, 2023, 2024 and 2025. It belongs to Enthalpy and Hess's Law, in Thermodynamics (Chemistry) (Chemistry). The longest wait between two years asking it was 2 years. In 2021 it came in more than one shift of the same year.

Updated 2026-10-24

Times asked
5
in 5 shifts
Years
4 of 8
First asked
2021
last in 2025
Pattern
Comes in cycles
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2021, 2023, 2024 and 2025. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Chemistry questions.

00.10.20’170’200.07’210’220.07’230.05’240.13’250’26

Raw count: 2017: 0 in 1 shift · 2020: 0 in 12 shifts · 2021: 2 in 24 shifts · 2022: 0 in 24 shifts · 2023: 1 in 12 shifts · 2024: 1 in 18 shifts · 2025: 1 in 8 shifts · 2026: 0 in 9 shifts.

Shift by shift

Each square is one analysed shift, in date order. Open a filled one for that paper.

  • 20260 of 9
  • 20251 of 8
  • 20241 of 18
  • 20231 of 12
  • 20220 of 24
  • 20212 of 24
  • 20200 of 12
  • 20170 of 1

Asked in that shift More than once Not asked

How JEE Main framed it

Numerical value is the usual form. Skill tested: calculation.

  • Enthalpy of formation from bond enthalpies
  • Reaction enthalpy from bond enthalpies

Difficulty

Easy 2Medium 3Hard 0

5 of the 5 questions had a numerical answer.

Every question

All 5 questions

From the official JEE Main shift papers, newest first. Open one for the full question, the options and the official answer.

  1. 3 Apr 2025, Shift 1 · Q71Given : ΔHsub⊖\Delta H^{\ominus}_{sub} [C (graphite)] = 710 kJ mol−1^{-1} ΔC−HH⊖\Delta_{C-H}H^{\ominus} = 414 kJ mol−1^{-1}…MediumNumerical value
  2. 4 Apr 2024, Shift 1 · Q83The enthalpy of formation of ethane (C2H6\mathrm{C_2H_6}) from ethylene by addition of hydrogen where the bond-energies of C−-H, C−-C,…EasyNumerical value
  3. 13 Apr 2023, Shift 1 · Q83A2+B2→2AB\mathrm{A_2}+\mathrm{B_2}\rightarrow 2\mathrm{AB}. ΔHf0=−200 kJ mol−1\Delta H_f^0 = -200\ \mathrm{kJ\ mol^{-1}} AB, A2\mathrm{A_2} and B2\mathrm{B_2}…MediumNumerical value
  4. 18 Mar 2021, Shift 1 · Q53For the reaction C2H6→C2H4+H2\mathrm{C_2H_6 \rightarrow C_2H_4 + H_2} the reaction enthalpy ΔrH=\Delta_rH = __________ kJ mol−1^{-1}. (Round off to…EasyNumerical value
  5. 26 Feb 2021, Shift 2 · Q54The average S−-F bond energy in kJ mol−1\mathrm{mol^{-1}} of SF6\mathrm{SF_6} is __________. (Rounded off to the nearest integer) [Given :…MediumNumerical value

Shifts: 26 Feb 2021, Shift 2, 18 Mar 2021, Shift 1, 13 Apr 2023, Shift 1, 4 Apr 2024, Shift 1, 3 Apr 2025, Shift 1.

Same topic

Other ideas in Enthalpy and Hess's Law

Enthalpy and Hess's Law has 23 ideas JEE Main has asked; 12 of them came up in more than one question. The 12 most asked are below.

Topic analysisChapter analysisStudy this chapterAll repeated ideas