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Friday, 9 October

JEE Main Chemistry · Thermodynamics (Chemistry)

Enthalpy and Hess's Law in JEE Main

Enthalpy and Hess's Law (Chemistry, Thermodynamics (Chemistry)) came 24 times in 21 of the 42 JEE Main shifts Lumi analysed, across 14 distinct ideas. 15 of them came in 2024–26; it was last asked in 2026.

Questions
24
in 21 shifts
Ideas asked
14
6 asked more than once
Numerical answer
15
63% of its questions
Pattern
Asked most years
last asked 2026
Questions each year
0481’171’202’213’222’233’248’254’26

In the shifts Lumi analysed for each year.

Difficulty and format
Easy 14Medium 7Hard 3

Format

  • Numerical value15 Q
  • Single correct7 Q
  • Two statements2 Q
Ideas inside the topic
14 ideas
Where it sits

Part of Thermodynamics (Chemistry), which had 51 questions in all. Enthalpy and Hess's Law accounts for 47% of them. In Lumi's JEE taxonomy it belongs to Physical Chemistry.

Some questions sit in other chapters too: Chemical Bonding and Molecular Structure, Solutions, States of Matter.

Every question

All 24 Enthalpy and Hess's Law questions

Newest first, each with its options and 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. 4 Apr 2026, Shift 1 · Q54Given below are two statements: Statement I: For an ideal gas, heat capacity at constant volume is always greater than the heat capacity…EasyTwo statements
  3. 4 Apr 2026, Shift 2 · Q71If 3.365 g of ethanol (ll) is burnt completely in a bomb calorimeter at 298.15 K, the heat produced is 99.472 kJ. The…HardNumerical value
  4. 8 Apr 2026, Shift 2 · Q74Consider the reaction 2H2S(g)+3O2(g)→2H2O(l)+2SO2(g)2\mathrm{H_2S(g)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{H_2O(l)} + 2\mathrm{SO_2(g)} The magnitude of enthalpy…EasyNumerical value
  5. 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
  6. 3 Apr 2025, Shift 2 · Q53Given below are two statements: Statement I : When a system containing ice in equilibrium with water (liquid) is heated, heat is absorbed…EasyTwo statements
  7. 3 Apr 2025, Shift 2 · Q72A sample of n-octane (1.14 g) was completely burnt in excess of oxygen in a bomb calorimeter, whose heat capacity is 5 kJ…MediumNumerical value
  8. 4 Apr 2025, Shift 2 · Q52Consider the given data : (a) HCl(g)+10 H2O(l)→HCl.10 H2O\mathrm{HCl(g)+10\ H_2O(l)\rightarrow HCl.10\ H_2O} ΔH=−69.01\Delta H=-69.01 kJ mol−1^{-1} (b)…MediumSingle correct
  9. 7 Apr 2025, Shift 1 · Q53Total enthalpy change for freezing of 1 mol of water at 10∘10^\circC to ice at −10∘-10^\circC is __________ (Given: ΔfusH=x\Delta_{fus}H = x…MediumSingle correct
  10. 7 Apr 2025, Shift 2 · Q52The correct statement amongst the following is :MediumSingle correct
  11. 7 Apr 2025, Shift 2 · Q53The hydration energies of K+\mathrm{K^+} and Cl−\mathrm{Cl^-} are −x-x and −y-y kJ/mol respectively. If lattice energy of KCl is −z-z…EasySingle correct
  12. 8 Apr 2025, Shift 2 · Q73Resonance in X2Y\mathrm{X_2Y} can be represented as…HardNumerical valueHas a figure
  13. 9 Apr 2024, Shift 1 · Q83The heat of solution of anhydrous CuSO4\mathrm{CuSO_4} and CuSO4⋅5H2O\mathrm{CuSO_4\cdot5H_2O} are −70-70 kJ mol−1^{-1} and +12+12 kJ mol−1^{-1}…EasyNumerical value
  14. 9 Apr 2024, Shift 1 · Q84When equal volume of 1M HCl and 1M H2SO4\mathrm{H_2SO_4} are separately neutralised by excess volume of 1M NaOH solution, xx and yy kJ of…EasyNumerical value
  15. 30 Jan 2024, Shift 2 · Q82Two reactions are given below:…EasyNumerical value
  16. 8 Apr 2023, Shift 2 · Q83For complete combustion of ethene, C2H4(g)+3O2(g)→2CO2(g)+2H2O(l)\mathrm{C_2H_4(g) + 3O_2(g) \rightarrow 2CO_2(g) + 2H_2O(l)} the amount of heat produced as measured…MediumNumerical value
  17. 11 Apr 2023, Shift 1 · Q83Solid fuel used in rocket is a mixture of Fe2O3\mathrm{Fe_2O_3} and Al (in ratio 1:2). The heat evolved (kJ) per gram of the mixture is…MediumNumerical value
  18. 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
  19. 28 Jul 2022, Shift 1 · Q62Which of the following relation is not correct ?EasySingle correct
  20. 29 Jun 2022, Shift 1 · Q8217.0 g of NH3\mathrm{NH_3} completely vapourises at −33.42∘C-33.42^\circ\mathrm{C} and 1 bar pressure and the enthalpy change in the process is…EasyNumerical value
  21. 25 Jul 2021, Shift 1 · Q55At 298 K, the enthalpy of fusion of a solid (X) is 2.8 kJ mol−1^{-1} and the enthalpy of vaporisation of the liquid (X) is 98.2 kJ…EasyNumerical value
  22. 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
  23. 2 Sep 2020, Shift 1 · Q46The internal energy change (in J) when 90 g of water undergoes complete evaporation at 100∘100^\circC is ______. (Given : ΔHvap\Delta H_{vap}…EasyNumerical value
  24. 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