Chemical Thermodynamics — JEE Main PYQs & Practice Questions

Chemical Thermodynamics is a Chemistry chapter in the JEE Main syllabus. This page brings together 161 previous-year and practice questions on Chemical Thermodynamics, organised into 7 topics: First Law and Internal Energy, Enthalpy and Heat Capacity, Hess's Law, Bond Enthalpy, Lattice Energy and Born-Haber Cycle, Entropy and Spontaneity and Gibbs Free Energy. Most questions come with a step-by-step solution you can work through free in PrepWiser.

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Chapter weightage: how many questions each chapter had per shift in the 2024–26 papers.

First Law and Internal Energy

• The internal energy change (in J) When 90 g of water undergoes complete evaporation at…
• Five moles of an ideal gas at 1 bar and 298 K is expanded into vacuum to double the…
• If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under…
• 1 mole of ideal gas is allowed to expand reversibly and adiabatically from a temperature…
• What happens when methane undergoes combustion in systems A and B respectively?
• Which of the following relations are correct? (A) Δ U=q+pΔ V (B) Δ G=Δ H-TΔ S (C) Δ…
• An ideal gas undergoes a cyclic transformation starting from the point A and coming back…
• Arrange the following isothermal processes in order of the magnitude of the work (p-V)…
• Match the LIST-I with LIST-II List-I Thermodynamic Process | List-II Magnitude in kJ; A…
• One mole of an ideal gas expands isothermally and reversibly from 10 dm³ to 20 dm³ at…
• Choose the correct option for free expansion of an ideal gas under adiabatic condition…
• Gas 'A' undergoes change from state 'X' to state 'Y'. In this process, the heat absorbed…
• Among the following the number of state variables is ______________. Internal energy (U)…
• One mole of an ideal monoatomic gas is subjected to changes as shown in the graph. The…
• If three moles of an ideal gas at 300 K expand isothermally from 30 dm³ to 45 dm³…
• At constant volume, 4 mol of an ideal gas when heated from 300 K to 500K changes its…
• Match List - I with List - II. Given V₁ and V₂ are initial and final volumes…
• 2.2 g of nitrous oxide (N₂O) gas is cooled at a constant pressure of 1 atm from 310 K to…
• The total number of intensive properties from the following is __________ Volume, Molar…
• 20.0dm³ of an ideal gas ' X ' at 600 K and 0.5 MPa undergoes isothermal reversible…

Enthalpy and Heat Capacity

• At 25°C and 1 atm pressure, the enthalpies of combustion are as given below : Substance…
• The correct statement amongst the following is :
• The process that is NOT endothermic in nature is :
• The correct order of molar heat capacities measured at 298 K and 1 bar is :
• The molar heat capacity for an ideal gas at constant pressure is 20.785 J K⁻¹ mol⁻¹. The…
• Solid fuel used in rocket is a mixture of Fe₂ O₃ and Al (in ratio 1 : 2). The heat…
• According to the following figure, the magnitude of the enthalpy change of the reaction…
• The plot of log₁₀ K vs 1/T gives a straight line. The intercept and slope respectively…
• 28.0 L of CO₂ is produced on complete combustion of 16.8 L gaseous mixture of ethene and…
• 0.3 g of ethane undergoes combustion at 27° C in a bomb calorimeter. The temperature of…
• Given below are two statements: One is labelled as Assertion (A) and the other is…
• 200 mL of 0.2 M HCl is mixed with 300 mL of 0.1 M NaOH. The molar heat of neutralization…
• When 600 mL of 0.2 M HNO₃ is mixed with 400 mL of 0.1 M NaOH solution in a flask, the…
• A fish swimming in water body when taken out from the water body is covered with a film…
• 17.0 g of NH₃ completely vapourises at -33.42°C and 1 bar pressure and the enthalpy…
• Standard enthalpy of vapourisation for CCl₄ is 30.5 kJ mol⁻¹. Heat required for…
• An average person needs about 10000 kJ energy per day. The amount of glucose (molar mass…
• 2.4 g coal is burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atm…
• For the reaction H₂ F₂( g) → H₂( g)+F₂( g) Δ U=-59.6 kJ mol⁻¹ at 27° C. The enthalpy…
• Which of the following mixing of 1 M base and 1 M acid leads to the largest increase in…

Hess's Law

• S( g)+3/2 O₂( g) → SO₃( g)+2 x kcal ; SO₂( g)+1/2 O₂( g) → SO₃( g)+y kcal The heat of…
• The standard enthalpies of formation of Al₂O₃ and CaO are -1675 kJ mol⁻¹ and -635 kJ…
• While performing a thermodynamics experiment, a student made the following observations…
• Consider the following cases of standard enthalpy of reaction (Δ Hᵣ° in kJ mol⁻¹) C₂ H₆(…
• The standard heat of formation ( Δ _fH₂₉₈⁰ ) of ethane (in kj/mol), if the heat of…
• At 25°C and 1 atm pressure, the enthalpy of combustion of benzene (I) and acetylene (g)…
• Consider the reaction 2H₂ S( g)+3O₂( g)→ 2H₂O(l)+2SO₂( g) The magnitude of enthalpy…
• In the given reaction cycle CaCl₂ + Na₂CO₃ @>>> X @. + Y ; @AAA @VVV @. ; @<Z<< @. X, Y…
• The enthalpy of combustion of propane, graphite and dihydrogen at 298 K are -2220.0 kJ…
• Two reactions are given below: 2 Fe₍ₛ₎+3/2 O_(2( g)) → Fe₂ O₃₍ₛ₎, Δ H°=-822 kJ / mol…
• Consider the following data : Heat of formation of CO₂(g)=-393.5 kJ mol ⁻¹ Heat of…
• Given (A) | 2CO(g)+O₂(g)→ 2CO₂(g) | Δ H₁⁰=-x kJ mol⁻¹; (B) | C(graphite)+O₂(g)→ CO₂(g) |…
• If 3.365 g of ethanol (l) is burnt completely in a bomb calorimeter at 298.15 K , the…
• Combustion of 1 mole of benzene is expressed at C₆ H₆(l)+15/2 O₂( g) → 6 CO₂( g)+3 H₂…
• Consider the following data Heat of combustion of H₂(g) =-241.8 kJ mol⁻¹ Heat of…
• Consider the following data. (i) 2Al(s)+6HCl(aq)→ Al₂Cl₆(aq)+3H₂(g)+1200 kJ/mol (ii)…
• The heat of solution of anhydrous CuSO₄ and CuSO₄ · 5 H₂ O are -70 kJ mol⁻¹ and +12 kJ…
• If C (diamond ) → C (graphite) +X kJ mol⁻¹ C (diamond) +O₂( g) → CO₂( g)+Y kJ mol ⁻¹ C…

Bond Enthalpy

• Resonance in X₂ Y can be represented as Ẍ(⊖) = X = Ÿ(⊕) ↔ :X ≡ X(⊕) - Ÿ(⊖): The…
• The formation enthalpies, Δ H_f⊖ for H_((g)) and O_((g)) are 220.0 and 250.0 kJ mol⁻¹…
• The enthalpy of formation of ethane (C₂ H₆) from ethylene by addition of hydrogen where…
• Arrange the following bonds according to their average bond energies in descending order…
• The correct order of bond enthalpy (kJ mol⁻¹) is :
• The average S-F bond energy in kJ mol⁻¹ of SF₆ is _____________. (Rounded off to the…
• Consider the following data : Δ_fH° (methane, g) = -X kJ mol⁻¹ Enthalpy of sublimation…
• If enthalpy of atomisation for Br₂₍₁₎ is x kJ/mol and bond enthalpy for Br₂ is y kJ/mol…
• At 298.2 K the relationship between enthalpy of bond dissociation (in kJ mol⁻¹) for…
• For the reaction C₂H₆ → C₂H₄ + H₂ the reaction enthalpy ΔᵣH = __________ kJ mol⁻¹…
• Given : Δ H⊖ _(sub)[C (graphite )]=710 kJ mol⁻¹ ; Δ_(C-H) H⊖=414 kJ mol⁻¹ ; Δ_(H-H)…
• A₂+B₂ → 2 AB . Δ H_f⁰=-200 kJ mol⁻¹ AB, A₂ and B₂ are diatomic molecules. If the bond…
• The bond dissociation energy is highest for
• The heat of atomisation of methane and ethane are ' x ' kJmol⁻¹ and ' y ' kJmol⁻¹…

Lattice Energy and Born-Haber Cycle

• The ionization enthalpy of Na⁺ formation from Na (g) is 495.8 kJ mol⁻¹, while the…
• Identify the correct order of standard enthalpy of formation of sodium halides :
• The Born-Haber cycle for KCl is evaluated with the following data : Δ _fH^Θ for KCl =…
• If the enthalpy of sublimation of Li is 155 kJ mol⁻¹, enthalpy of dissociation of F₂ is…
• The bond dissociation enthalpy of X₂ Δ H_(bond)° calculated from the given data is…
• Lattice enthalpy and enthalpy of solution of NaCl are 788 kJ mol –1 , and 4 kJ mol –1…
• The hydration energies of K⁺ and Cl⁻ are -x and -y kJ/mol respectively. If the lattice…

Entropy and Spontaneity

• Ice at -5° C is heated to become vapor with temperature of 110° C at atmospheric…
• When Δ Hᵥₐₚ=30 kJ / mol and Δ Sᵥₐₚ=75 J mol⁻¹ K⁻¹, then the temperature of vapour, at…
• For independent process at 300 K Process | Δ H/kJ mol⁻¹ | Δ S/J K⁻¹; A | -25 | -80; B |…
• During which of the following processes, does entropy decrease? (A) Freezing of water to…
• Standard entropies of X₂, Y₂ and XY₅ are 70, 50 and 110 J K⁻¹ mol⁻¹ respectively. The…
• One mole of an ideal gas at 350 K is in a 2.0 L vessel of thermally conducting walls…
• Given below are two statements: One is labelled as Assertion A and the other is labelled…
• For complete combustion of ethene. C₂ H₄(g)+3 O₂(g) → 2 CO₂(g)+2 H₂ O(l) the amount of…
• The true statement amongst the following is :

Gibbs Free Energy

• The effect of temperature on spontaneity of reactions are represented as : ΔH | ΔS |…
• The standard enthalpy and standard entropy of decomposition of N₂ O₄ to NO₂ are 55.0 kJ…
• Consider the reaction X⇌ Y at 300 K . If ΔH^θ and K are 28.40 kJ mol⁻¹ and 1.8× 10⁻⁷ at…
• For a dimerization reaction, 2A(g) → A₂(g) at 298 K, ΔUᵒ = –20 kJ mol –1 , ΔSᵒ = –30 JK…
• ΔG° vs T plot for the formation of MgO, involving reaction 2Mg + O₂ → 2MgO, will look…
• For the reaction, 2NO₂(g) ⇌ N₂O₄(g), when ΔS = -176.0 JK⁻¹ and ΔH = -57.8 kJ mol⁻¹, the…
• The incorrect expression among the following is :
• For the reaction at 298 K, 2 A+B → C, Δ H=400 kJ mol⁻¹ and Δ S=0.2 kJ mol⁻¹ K⁻¹. The…
• Which of the following graphs correctly represents the variation of thermodynamic…
• For the reaction : A(l) → 2B(g) Δ U = 2.1 kcal, Δ S = 20 cal K⁻¹ at 300 K Hence ΔG in…
• The value of log K for the reaction A ⇌ B at 298 K is ___________. (Nearest integer)…
• At the transition temperature T, A⇌ B and Δ G⁰=105-35 log T where A and B are two states…
• For a given chemical reaction A → B at 300 K the free energy change is -49.4 kJ mol⁻¹…
• For a chemical reaction A + B ⇌ C + D (Δ ᵣH^Θ = 80 kJ mol⁻¹) the entropy change Δ ᵣS^Θ…
• For a certain thermochemical reaction M → N at T=400 K, Δ H⊖=77.2 kJ mol⁻¹, Δ S=122…
• Use the following data:; Substance, Δ_fH⊖(500 K)/(kJ mol⁻¹), S⊖(500 K)/(JK⁻¹ mol⁻¹); AB(…
• Consider the following data for the reaction X₂(g)+Y₂(g)⇌ 2XY(g) at 600 K°. The ΔᵣG⊖ (in…
• Which of the following is not correct?
• Data given for the following reaction is as follows : FeO₍ₛ₎ + C (graphite) → Fe₍ₛ₎ + CO…
• Match List-I with List-II. List - I | List - II; (A) | Spontaneous process | (I) | Δ H <…

More Chemistry chapters

• Mole Concept & Stoichiometry
• Atomic Structure
• Gaseous State
• Chemical Equilibrium
• Ionic Equilibrium
• Redox Reactions
• Solutions & Colligative Properties
• Electrochemistry
• Chemical Kinetics
• Solid State
• Surface Chemistry
• Nuclear & Radiochemistry
• Periodic Table & Periodicity
• Chemical Bonding & Molecular Structure
• Hydrogen & s-Block Elements
• p-Block Elements — Part I (Group 13 & 14)
• Environmental Chemistry
• p-Block Elements — Part II (Group 15-18)
• d & f Block Elements
• Coordination Compounds
• Metallurgy
• Qualitative Analysis — Salt Analysis
• Purification & Characterisation of Organic Compounds
• General Organic Chemistry (GOC)
• Hydrocarbons — Alkanes
• Hydrocarbons — Alkenes & Alkynes
• Hydrocarbons — Aromatic (Arenes)
• Halogen Derivatives — Haloalkanes & Haloarenes
• Alcohols, Phenols & Ethers
• Aldehydes & Ketones
• Carboxylic Acids & Their Derivatives
• Amines & Diazonium Salts
• Carbohydrates & Biomolecules
• Polymers
• Chemistry in Everyday Life
• Practical Organic Chemistry

Frequently asked questions

How many Chemical Thermodynamics questions are there for JEE Main?

PrepWiser has 161 Chemical Thermodynamics questions for JEE Main, grouped into 7 topics such as First Law and Internal Energy, Enthalpy and Heat Capacity and Hess's Law.

Are these Chemical Thermodynamics questions from previous-year JEE Main papers?

Yes — most are genuine previous-year questions from past JEE Main papers, and the rest are practice questions written to match the JEE Main pattern and difficulty.

Where can I see the answers and solutions to these Chemical Thermodynamics questions?

Open any Chemical Thermodynamics question in PrepWiser (it is free) to attempt it; most come with a step-by-step solution.