JEE Chemistry

Hess's Law: JEE Questions & Solutions

9 previous-year JEE Chemistry questions on Hess's Law, each with a worked step-by-step solution.

Intermediate

Previous-year questions

  1. 01If the enthalpy of sublimation of Li is 155 kJ mol⁻¹, enthalpy of dissociation of F₂ is 150 kJ mol⁻¹, ionization enthalpy of Li is 520 kJ…NVAMediumJEE 2026
  2. 02Consider the following cases of standard enthalpy of reaction (Δ H_r^° in kJ mol⁻¹): C₂H₆(g) + 7/2 O₂(g) → 2 CO₂(g) + 3 H₂O(l) Δ H₁^° =…NVAMediumJEE 2025
  3. 03S(g) + 3/2 O₂(g) → SO₃(g) + 2x kcal SO₂(g) + 1/2 O₂(g) → SO₃(g) + y kcal The heat of formation of SO₂(g) is given by:MCQMediumJEE 2025
  4. 04If C(diamond) → C(graphite) + X kJ mol⁻¹ C(diamond) + O₂(g) → CO₂(g) + Y kJ mol⁻¹ C(graphite) + O₂(g) → CO₂(g) + Z kJ mol⁻¹ at constant…MCQEasyJEE 2025
  5. 05Two reactions are given below: 2Fe(s) + 3/2O₂(g) → Fe₂O₃(s), Δ H^° = -822 kJ/mol C(s) + 1/2O₂(g) → CO(g), Δ H^° = -110 kJ/mol The enthalpy…MCQEasyJEE 2024
  6. 06The enthalpy change for the conversion of 1/2 Cl₂(g) → Cl⁻(aq) is (-)..... kJ mol⁻¹ (Nearest integer) Given: Δ_fH^°(Cl₂(g)) = 240 kJ mol⁻¹,…NVAEasyJEE 2023
  7. 07At 25^° C, the enthalpy of the following processes are given: H₂(g) + O₂(g) → 2OH(g) Δ H^° = 78 kJ mol⁻¹ H₂(g) + 1/2 O₂(g) → H₂O(g) Δ H^° =…NVAMediumJEE 2023
  8. 08Consider the following data: Heat of combustion of H₂(g) = -241.8 kJ mol⁻¹ Heat of combustion of C(s) = -393.5 kJ mol⁻¹ Heat of combustion…NVAEasyJEE 2023
  9. 09Given: (A) 2CO(g) + O₂(g) → 2CO₂(g), Δ H₁^° = -x kJ mol⁻¹ (B) C(graphite) + O₂(g) → CO₂(g), Δ H₂^° = -y kJ mol⁻¹ The Δ H^° for the reaction…MCQMediumJEE 2023

Frequently asked questions

Our bank has 9 previous-year JEE Chemistry questions tagged to Hess's Law, drawn from JEE papers between 2023 and 2026, including 1 from 2026 alone. Each comes with a full step-by-step solution.

Hess's Law is rated Intermediate overall for JEE Chemistry. The PYQs on this page break down as 5 medium, 4 easy.

Of the 9 previous-year questions on Hess's Law, 4 are multiple-choice (MCQ) and 5 are numerical-value (NVA) questions.

Based on recent paper analysis, Hess's Law is worth about 1 mark in JEE Main. It sits in Chemical Thermodynamics, a Class 11 Chemistry chapter.

More Chemical Thermodynamics topics

Internal Energy & Enthalpy31Gibbs Free Energy & Equilibrium Constant12Enthalpies (Bond, Combustion, Formation…)10Entropy & Spontaneity6System & Surroundings2

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