If you are wondering how to study Chemical Thermodynamics for JEE, start with two numbers. JEE Main asked 75 questions from this chapter across 2024, 2025 and 2026, and JEE Advanced asked 25 questions from it between 2015 and 2026, with at least one in every single year. This guide breaks those questions down by sub-topic, based on the papers conducted by the National Testing Agency (jeemain.nta.ac.in) for JEE Main and the JEE Advanced papers from 2015 to 2026.
We went through every one of those questions and sorted each into one of four groups: the first law with work and processes, thermochemistry, entropy and Gibbs energy, and basic concepts such as standard states and heat capacities. The tables below show exactly where the marks come from, and the rest of the guide shows how to win them.
Chemical Thermodynamics also overlaps with Physics. The first law, work in isothermal and adiabatic processes and p–V graphs appear in both subjects with the same equations. The only thing that changes is the sign convention, which we cover below. Learn the overlap once and you gain marks in two papers.
It gives you at least one question in almost every JEE Main shift. JEE Main had 22 questions from this chapter in 2024, 31 in 2025 and 22 in 2026. That is 3.67%, 6.53% and 4.63% of all Chemistry questions in those years. In 2025, the busiest year, it averaged more than 1.5 questions per paper.
It is one of the most consistent chapters in JEE Advanced. JEE Advanced asked 25 questions from this chapter between 2015 and 2026 and never skipped a year. 12 of those 25 were numerical-answer questions, so the chapter rewards students who can calculate carefully without options to guide them.
The format is changing. In 2024, 19 of the 22 JEE Main questions were numericals. In 2026, 16 of the 22 were MCQs, many of them matching or statement questions about processes and signs. A plan that only drills calculations is now half a plan. You also need to read a process and decide the signs of q, w and ΔU in seconds.
It is the base of Physical Chemistry. ΔG° = −RT ln K links this chapter to Equilibrium, and ΔG = −nFE links it to Electrochemistry. Weakness here shows up as lost marks in both of those chapters.
"Most thermodynamics mistakes are not calculation mistakes. They are sign mistakes. Fix one sign convention, write the system and the surroundings clearly at the start, and half of the wrong answers disappear." — AN Naik Sir, Chemistry HOD (IIT BHU, Ex-HOD Narayana Academy Hyderabad)
Real result · JEE 2026
Thermodynamics marks are lost to signs and units far more than to hard ideas. Learn this chapter 1-on-1 with an IITian Chemistry HOD who checks every sign with you until it is automatic.
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Any plan for how to study Chemical Thermodynamics for JEE should start from the papers. Here is how many questions JEE Main asked from this chapter in each of the last three years.
| Year | Questions | MCQ + Numerical | Share of Chemistry Qs |
|---|---|---|---|
| 2024 | 22 | 3 + 19 | 3.67% |
| 2025 | 31 | 21 + 10 | 6.53% |
| 2026 | 22 | 16 + 6 | 4.63% |
| Total | 75 | 40 + 35 | — |
And here are the same 75 questions sorted by what they actually test.
| Sub-topic | 2024 | 2025 | 2026 | Total |
|---|---|---|---|---|
| Thermochemistry (Hess's law, enthalpies of formation and combustion, bond enthalpy, Born–Haber cycle, heats of solution and neutralisation, calorimetry) | 10 | 13 | 6 | 29 |
| First law, work and processes (signs of q, w and ΔU; isothermal, adiabatic and free expansion; p–V graphs; cycles) | 7 | 7 | 8 | 22 |
| Entropy, Gibbs energy and spontaneity (ΔG = ΔH − TΔS, temperature for spontaneity, ΔG° and K) | 5 | 8 | 6 | 19 |
| Basic concepts (standard state, heat capacities, Cp and Cv, phase behaviour) | 0 | 3 | 2 | 5 |
| Total | 22 | 31 | 22 | 75 |
Questions that test two ideas are counted once, under the idea they mainly test.
Thermochemistry is the biggest block: 29 of 75 questions, close to two in every five. The first law gives another 22, and it is the sub-topic that grew most clearly in 2026, when it gave 8 of the 22 questions. Entropy and Gibbs energy are steady at 5 to 8 a year. Together, the three main sub-topics cover 70 of the 75 questions.
Pattern 1: Ordering and matching work in isothermal processes. The same idea appeared at least four times in two years. 2026 asked students to match reversible expansion, free expansion, irreversible compression and a reversible cycle to their work expressions (twice, in different shifts), and to order single-stage and multi-stage expansions and compressions by the size of the work. 2025 asked the same ordering for reversible and single-stage irreversible expansion and compression. If you know why irreversible compression needs the most work and free expansion does none, these are 60-second marks.
Pattern 2: Signs of q, w and ΔU in a real situation. A cup of water at 5 °C heated in a microwave until it boils (2026). A liquid stirred inside a thermally insulated closed vessel (2025). A gas expanding into an evacuated vessel through a stopcock (2025). Adiabatic free expansion of an ideal gas (2024). Each one asks the same thing: define the system, then decide which of q, w and ΔU are positive, negative or zero.
Pattern 3: Bond enthalpy and Born–Haber numericals. The lattice enthalpy of LiF from a Born–Haber cycle (2026), the average O–H bond enthalpy in water (2025), the resonance energy of a molecule from bond enthalpies and its enthalpy of formation (2025), and the enthalpy of formation of ethane from bond energies (2024) all used the same bookkeeping: bonds broken minus bonds formed, or a cycle that must add to zero.
Pattern 4: Calorimetry and the gap between ΔU and ΔH. A bomb calorimeter measures heat at constant volume, which is ΔU, not ΔH. 2026 asked for the enthalpy of formation of ethanol from bomb-calorimeter data, 2025 for the heat of combustion of n-octane at constant volume, and 2024 for the constant-pressure heat of combustion of benzoic acid from its constant-volume value and for ΔU of vaporisation of water. The link is always ΔH = ΔU + ΔngRT.
Pattern 5: The temperature at which a reaction becomes spontaneous. 2024 asked for the temperature above which a reaction is spontaneous and for a boiling temperature from ΔHvap and entropy. 2025 asked for the temperature at which a reaction reaches equilibrium, and the signs of ΔH and ΔS for a reaction that is non-spontaneous at 0 °C but spontaneous at 100 °C. 2026 asked for a transition temperature at 1 atm. All of them come from setting ΔG = 0, so T = ΔH/ΔS.
This is the 12-year view that most guides skip. JEE Advanced has asked this chapter in every year from 2015 to 2026.
| Year | Qs | What was asked |
|---|---|---|
| 2026 | 2 | Ideal gas compressed isothermally in two steps: the intermediate pressure that minimises the work (single correct) · physisorption, diamond → graphite, protein denaturation and propene → cyclopropane matched to signs of ΔH and ΔS (matching) |
| 2025 | 1 | Expansion work done when 144 g of water is completely electrolysed at 300 K and constant pressure (numerical) |
| 2024 | 1 | Enthalpy change of 5 mol of a monoatomic ideal gas over a sequence of states on a volume–temperature diagram (numerical) |
| 2023 | 4 | ΔS and ΔH for a change from state α to state β (two numericals) · two reversible processes including an adiabatic step, total heat (numerical) · ΔG° from a reaction studied at two temperatures in a 1 L flask (numerical) |
| 2022 | 2 | Standard enthalpy of formation from bomb-calorimeter data with a temperature rise (numerical) · statements about entropy (multi-correct) |
| 2021 | 4 | ΔH° and ΔS° for X(s) ⇌ Y(s) + Z(g) (two numericals) · two reversible processes from 900 K doing equal work (numerical) · reversible isothermal then adiabatic expansion: which p–V, V–T, H and S plots are correct (multi-correct) |
| 2020 | 2 | Minimum temperature for reducing cassiterite with coke (numerical) · which process a given p–V work expression applies to (multi-correct) |
| 2019 | 1 | Reactions for which the standard enthalpy of reaction equals the standard enthalpy of formation (multi-correct) |
| 2018 | 3 | Minimum partial pressure of H2 needed to stop copper being oxidised by water vapour (numerical) · plots of thermodynamic quantities with time for A ⇌ P at two temperatures (multi-correct) · reversible cyclic process: q, w, ΔH and ΔU (multi-correct) |
| 2017 | 3 | Graphite → diamond: equilibrium pressure from Gibbs energies of formation and the volume change (single correct) · effect of temperature on K in terms of entropy change (multi-correct) · ideal gas expanded under different conditions (multi-correct) |
| 2016 | 1 | Entropy change of the surroundings for isothermal expansion of 1 mol of ideal gas against 3 atm at 300 K (single correct) |
| 2015 | 1 | Freezing water, expansion into vacuum, mixing of ideal gases and reversible heating of H2 matched to q, w, ΔS and ΔU (matching) |
| Total | 25 | 12 numerical · 8 multi-correct · 3 single correct · 2 matching |
One 2019 question on rms speed and kinetic energy of gas molecules, filed under this chapter in the archive, belongs to States of Matter and is not counted.
The Advanced pattern is close to the Main one, with one shift in weight. Entropy and Gibbs energy give the most Advanced questions (12 of 25), especially ΔG° and K with real systems: graphite and diamond, cassiterite, copper oxidation. The first law and processes give 10, and thermochemistry only 3. In Main it is the other way round: thermochemistry leads. So if you are writing JEE Advanced, give Gibbs energy more time than the Main data alone would suggest.
The smartest way to decide how to study Chemical Thermodynamics for JEE is to match your time to each sub-topic. Use the time column in your mock tests: if you are consistently slower than the target, that sub-topic needs more practice, not more reading.
| Sub-topic | Main Qs (2024–26) | Advanced Qs (2015–26) | Difficulty | Target time |
|---|---|---|---|---|
| Thermochemistry | 29 | 3 | Easy–Medium | 90 s–2 min |
| First law, work and processes | 22 | 10 | Medium | 60 s for sign questions · 2–3 min for work numericals |
| Entropy, Gibbs energy and spontaneity | 19 | 12 | Medium–Hard | 90 s–3 min |
| Basic concepts | 5 | 0 | Easy | 30–60 s |
Difficulty and target time are our faculty's guidance for exam practice, not exam data.
Thermochemistry covers Hess's law, enthalpies of formation and combustion, bond enthalpies, Born–Haber cycles, heats of solution, hydration and neutralisation, phase-change enthalpies and bomb calorimetry. It is the largest block in JEE Main and mostly numerical.
First law, work and processes covers ΔU = q + w, work in reversible, irreversible and free expansions, adiabatic processes, cycles and p–V graphs. In 2026 it moved towards matching and ordering MCQs.
Entropy, Gibbs energy and spontaneity covers ΔS for phase changes and processes, the second law, ΔG = ΔH − TΔS, the sign table for spontaneity, and ΔG° = −RT ln K. It is the most important sub-topic for JEE Advanced.
Basic concepts covers standard states, extensive and intensive properties, heat capacities and the relation between Cp and Cv. It gives few questions, but they are the fastest marks in the chapter.
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Thermochemistry and the first law gave two-thirds of this chapter's JEE Main questions from 2024 to 2026. Work through both with your own faculty, at your pace, with every doubt answered the same day.
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Knowing how to study Chemical Thermodynamics for JEE also means knowing what not to do. These are the mistakes we see most often when students solve this chapter's PYQs.
Keep this table open while you practise. Most of the chapter runs on these results, which is why learning how to study Chemical Thermodynamics for JEE is mostly about applying them quickly and without sign errors.
| Sub-topic | Formula / result |
|---|---|
| First law | ΔU = q + w (Chemistry convention: work done on the system is positive) |
| Work, constant external pressure | w = −pext(V2 − V1) · free expansion (pext = 0): w = 0 |
| Reversible isothermal work | w = −2.303 nRT log(V2/V1) = −2.303 nRT log(p1/p2) · ideal gas: ΔU = 0, q = −w |
| Adiabatic process | q = 0, w = ΔU = nCv(T2 − T1) · reversible: TVγ−1 = constant, pVγ = constant |
| Heat capacities | Cp − Cv = R (ideal gas, per mole) · monoatomic: Cv = 3R/2, Cp = 5R/2 · diatomic: Cv = 5R/2, Cp = 7R/2 |
| Enthalpy | H = U + pV · ΔH = ΔU + ΔngRT · qp = ΔH, qv = ΔU |
| Hess's law | ΔrH° = ΣΔfH°(products) − ΣΔfH°(reactants) · ΔfH° of an element in its standard state = 0 |
| Combustion | ΔrH° = ΣΔcH°(reactants) − ΣΔcH°(products) |
| Bond enthalpy | ΔrH = Σ(bond enthalpies of bonds broken) − Σ(bond enthalpies of bonds formed) · resonance energy = ΔfH(calculated) − ΔfH(observed) |
| Born–Haber / solution | ΔsolH = ΔlatticeH (breaking the lattice) + ΔhydH · the cycle's enthalpy changes add to zero |
| Neutralisation | Strong acid + strong base: about −57.3 kJ per mol of water formed · weak acid or base: less negative (part of the heat ionises it) |
| Calorimetry | q = CΔT (calorimeter) · q = mcΔT |
| Entropy | ΔS = qrev/T · phase change: ΔS = ΔH/T · heating: ΔS = nC ln(T2/T1) · ideal gas, isothermal: ΔS = nR ln(V2/V1) |
| Second law | ΔStotal = ΔSsystem + ΔSsurroundings > 0 for a spontaneous change · ΔSsurr = −qsystem/T |
| Gibbs energy | ΔG = ΔH − TΔS · ΔG < 0 spontaneous · ΔG = 0 at equilibrium, so T = ΔH/ΔS |
| Gibbs energy and K | ΔG° = −RT ln K = −2.303RT log K · ΔG = ΔG° + RT ln Q · log K = −ΔH°/(2.303RT) + ΔS°/(2.303R) |
| Link to Electrochemistry | ΔG = −nFE · ΔG° = −nFE° |
This is the core of how to study Chemical Thermodynamics for JEE: one sub-topic at a time, starting with the ones that have given the most marks. Do not move on until you can solve the PYQ type listed under each heading without notes.
Thermochemistry is bookkeeping. Every question gives you a set of known enthalpy changes and asks for an unknown one. There are four standard set-ups, and you should know which one you are in before you write anything:
Bomb calorimetry is the fifth idea in this group and appears every year. Convert heat at constant volume (ΔU) to heat at constant pressure (ΔH) with ΔH = ΔU + ΔngRT. For the combustion of benzoic acid, C6H5COOH(s) + 15/2 O2(g) → 7CO2(g) + 3H2O(l), Δng = 7 − 7.5 = −0.5.
Practice target: 25 thermochemistry PYQs, at least five of each set-up. Write which set-up it is in the margin before you start.
"For every thermochemistry question, I ask students to write the target equation first, with the states of every species. Once the target is on paper, the given data almost arranges itself. Students who start adding equations without a target get lost." — AN Naik Sir, Chemistry HOD (IIT BHU, Ex-HOD Narayana Academy Hyderabad)
This sub-topic has two kinds of question, and 2026 used both.
For p–V graphs, work is the area under the curve, and for a cycle the work is the area enclosed. ΔU for any complete cycle is zero, because U is a state function. 2025 tested exactly this with a cyclic process on a diagram, and 2024 asked for the total work in a cyclic transformation.
For adiabatic processes, remember that q = 0, so all the work changes U. 2024 asked for the final temperature after an adiabatic expansion against 1 atm. Because it is irreversible, use nCv(T2 − T1) = −pext(V2 − V1), not TVγ−1 = constant.
Practice target: 15 PYQs from this group, including every matching and ordering question from 2025 and 2026. For each, write q, w and ΔU with their signs before looking at the options.
"When I teach work, I draw the same two states and then four paths between them: reversible, single-stage, two-stage and free expansion. Once students see the four areas side by side, every ordering question becomes obvious." — AN Naik Sir, Chemistry HOD (IIT BHU, Ex-HOD Narayana Academy Hyderabad)
Learn this sub-topic as three connected tools:
For entropy changes along a path, split the path into heating steps and phase changes, as in the 2025 question that took ice at −5 °C to vapour. For the surroundings, ΔSsurr = −qsystem/T, which JEE Advanced 2016 asked for an isothermal expansion against 3 atm.
Practice target: 15 PYQs from this group, including every JEE Advanced ΔG° question from 2017 to 2023. Always convert ΔH to J before dividing by ΔS.
These are short, factual questions, and they are the easiest marks in the chapter:
Practice target: read the NCERT definitions of system, surroundings, state functions, extensive and intensive properties, and standard state once a week until they are automatic.
That is how to study Chemical Thermodynamics for JEE sub-topic by sub-topic. Once you have finished all four, test yourself under exam conditions with our JEE test series, and bring any question that still does not make sense to the JEE Doubt Lab for a 1-on-1 explanation.
Ready for exam-level practice?
JEE Advanced applies Gibbs energy to real systems and asks paired numericals on one reaction. Practise them 1-on-1 with an IITian Chemistry HOD who has taught them for years.
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If you are deciding how to study Chemical Thermodynamics for JEE Advanced as well as Main, this section is for you. Advanced uses the same syllabus but goes deeper in five places.
Advanced likes to put Gibbs energy into a real chemical situation: the pressure at which graphite and diamond are in equilibrium (2017), the minimum temperature to reduce cassiterite with coke (2020), and the minimum partial pressure of H2 that stops copper being oxidised by water vapour (2018). Each one needs ΔG = ΔG° + RT ln Q and the condition ΔG ≤ 0 or ΔG = 0.
Advanced 2021 asked for ΔH° and then ΔS° for the same decomposition, X(s) ⇌ Y(s) + Z(g), and Advanced 2023 asked for ΔS and then ΔH for a change from state α to state β. An error in the first answer carries into the second. Practise these as one problem and check the first answer before you use it.
Advanced 2021 asked which p–V, V–T, H and S plots correctly describe a reversible isothermal expansion followed by an adiabatic one. Advanced 2018 asked about plots of thermodynamic quantities with time as A ⇌ P approached equilibrium. For each step of a process, decide which quantities stay constant before you look at any graph: T in an isothermal step, S in a reversible adiabatic step, H for an ideal gas at constant T.
Advanced 2026 compressed a gas isothermally in two steps and asked for the intermediate pressure that makes the work smallest. Write the total work as a function of the intermediate pressure and minimise it. You will find it is the geometric mean of the initial and final pressures.
Advanced 2015 and 2026 had matching questions with four processes: freezing water, expansion into a vacuum, mixing ideal gases, protein denaturation, physisorption and similar. For each process, write the signs of q, w, ΔH, ΔS and ΔU on one line before you match anything.
"Advanced thermodynamics questions are long, but the chemistry inside them is short. Underline the process, write which quantity is zero, and the question is half solved before you start calculating." — AN Naik Sir, Chemistry HOD (IIT BHU, Ex-HOD Narayana Academy Hyderabad)
The last step in how to study Chemical Thermodynamics for JEE is an honest self-check. You should be able to answer "yes" to every line below without notes.
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Start the free test series →Chemical Thermodynamics gave JEE Main 75 questions from 2024 to 2026 and appeared in every JEE Advanced exam from 2015 to 2026, 25 questions in all. In JEE Main, thermochemistry gave 29 questions, the first law and processes 22, and entropy and Gibbs energy 19. In JEE Advanced, Gibbs energy led with 12. So if you are working out how to study Chemical Thermodynamics for JEE, the order is clear: fix your sign convention first, then master the four thermochemistry set-ups, then work in processes and the ordering questions, and finally entropy, the spontaneity table and ΔG° = −RT ln K, which Advanced asks most.
How we built this data. We went through every JEE Main shift paper from 2024, 2025 and 2026 and every JEE Advanced paper from 2015 to 2026, picked out each question from this chapter and tagged it by the main idea it tests. One Advanced question that the archive files under this chapter but belongs to another chapter is left out, as the footnote explains. No number on this page is estimated.
If you want a faculty member to check your preparation, every pack starts with a free 30-minute mentorship call. See all Chemistry chapter packs on our JEE Chemistry coaching page, and once your exam is done, our JEE counselling team can help you turn your rank into the right college and branch.
JEE Main asked 22 questions from this chapter in 2024 (3.67% of Chemistry questions), 31 in 2025 (6.53%) and 22 in 2026 (4.63%), counting all shifts. That is about one question per paper, and in 2025 often two.
JEE Main questions are mostly easy to medium. Most thermochemistry numericals are bookkeeping, and most process questions come down to signs. The difficulty is in sign conventions and units, not in ideas. JEE Advanced questions are harder because they apply ΔG° to real systems and use paired numericals. If you follow this guide on how to study Chemical Thermodynamics for JEE, the Main questions become routine with steady practice.
Yes. It was asked 75 times in JEE Main from 2024 to 2026 and in every JEE Advanced exam from 2015 to 2026. It is also the base for Equilibrium (ΔG° = −RT ln K) and Electrochemistry (ΔG = −nFE).
No. Skipping it gives up about one question per JEE Main paper, and it weakens Equilibrium and Electrochemistry as well. Because most Main questions follow a few fixed set-ups, it is one of the quickest Physical Chemistry chapters to turn into reliable marks.
Master thermochemistry first, then the first law with work in processes. In JEE Main 2024–2026 these two sub-topics gave 51 of the 75 questions, about two-thirds of the chapter. Add the spontaneity table and T = ΔH/ΔS and you cover 70 of 75.
JEE Advanced focuses more on entropy and Gibbs energy (12 of 25 questions from 2015 to 2026), especially ΔG° applied to real systems such as graphite and diamond, cassiterite reduction and copper oxidation. It also asks graphs of state functions and paired numericals on one reaction. 12 of the 25 Advanced questions were numerical-answer questions.
