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Saturday, 31 October

JEE Main · Chemistry · Thermodynamics (Chemistry)

Hess's Law

JEE Main asked Hess's Law 5 times in 5 of the 108 shifts Lumi analysed, in 2017, 2021, 2022, 2024 and 2026. It belongs to Enthalpy and Hess's Law, in Thermodynamics (Chemistry) (Chemistry). The longest wait between two years asking it was 4 years, across 2018 and 2019, which Lumi has no shifts for.

Updated 2026-10-24

Times asked
5
in 5 shifts
Years
5 of 8
First asked
2017
last in 2026
Pattern
Asked most years
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2017, 2021, 2022, 2024 and 2026. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Chemistry questions.

00.510.83’170’200.03’210.03’220’230.05’240’250.11’26

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

Shift by shift

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

  • 20261 of 9
  • 20250 of 8
  • 20241 of 18
  • 20230 of 12
  • 20221 of 24
  • 20211 of 24
  • 20200 of 12
  • 20171 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 via hess cycle
  • Enthalpy change via hess's law

Difficulty

Easy 3Medium 1Hard 1

3 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. 2 Apr 2026, Shift 1 · Q54Consider the following data. (i) 2Al(s)+6HCl(aq)→Al2Cl6(aq)+3H2(g)+1200\mathrm{2Al(s)+6HCl(aq)\rightarrow Al_2Cl_6(aq)+3H_2(g)}+1200 kJ/mol (ii)…HardSingle correct
  2. 30 Jan 2024, Shift 2 · Q82Two reactions are given below:…EasyNumerical value
  3. 25 Jul 2022, Shift 1 · Q82The enthalpy of combustion of propane, graphite and dihydrogen at 298 K are −2220.0 kJ mol−1-2220.0\ \mathrm{kJ\,mol^{-1}},…EasyNumerical value
  4. 4 Aug 2021, Shift 2 · Q55The standard reaction enthalpy for hydrogenation of propene is −124 kJ mol−1-124\ \mathrm{kJ\ mol^{-1}}. Additionally, standard heat of combustion…MediumNumerical value
  5. 2 Apr 2017 (offline) · Q31Given C(graphite)+O2(g)→CO2(g)\mathrm{C_{(graphite)}+O_2(g)\rightarrow CO_2(g)} ; ΔrH∘=−393.5 kJ mol−1\Delta_rH^\circ=-393.5\ \mathrm{kJ\,mol^{-1}}…EasySingle correct

Shifts: 2 Apr 2017 (offline), 4 Aug 2021, Shift 2, 25 Jul 2022, Shift 1, 30 Jan 2024, Shift 2, 2 Apr 2026, 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