Thermodynamics JEE Main Questions 2026: Important Practice Questions with PYQs

Thermodynamics JEE Main Questions 2026: What makes Thermodynamics different from other physics topics for JEE Mains 2026 is its very high potential for students to score marks in the JEE Mains 2026 exam. Often, experts recommend candidates who are preparing for the JEE Main 2026 to practise the Thermodynamics JEE Main Questions 2026 to successfully answer all the questions from this chapter. Moreover, solving as many questions from Thermodynamics for JEE Mains 2026 can help students to prepare well for the exams. Candidates can check this article on Thermodynamics JEE Main 2026 questions for more detailed knowledge.

Also Read: JEE Main Previous Year Question Paper

Section-Wise Thermodynamics Weightage JEE Main 2026

Check the section-wise Thermodynamics weightage JEE Main 2026 in the table below:

JEE Main 2025 Thermodynamics PYQs (Jan & April Sessions) with Solutions

Below are 12 recent Thermodynamics questions from JEE Main January 2025 (Shifts 1-2) and April 2025 (Shifts 1-2), sourced from official papers and expert analyses. These cover high-weightage sub-topics like First Law, processes, and Carnot efficiency. Solutions include step-by-step workings for exam-style practice.

JEE Main January 2025 Questions

Q1 (Jan 22 Shift 2 - First Law Application): 500 J of energy is transferred as heat to 2.5 moles of Argon at 298 K and 1 atm pressure. If the gas expands isothermally against constant pressure, calculate ΔU. (Nearest integer)

Solution: For ideal gas isothermal processes, ΔU = 0 (internal energy depends only on T). Answer: 0.

Q2 (Jan 23 Morning Shift - Enthalpy): The standard enthalpy and entropy of decomposition of CaCO₃(s) are +178 kJ/mol and +161 J/K mol. Above what temperature will the reaction be spontaneous? (R = 8.314 J/mol K)

Solution: ΔG = ΔH - TΔS = 0 at the spontaneity threshold. T = ΔH/ΔS = 178000 / 161 ≈ 1105 K.

Q3 (Jan 2025 - Adiabatic Expansion): 2 L ideal gas at 2 atm expands adiabatically to 6 L (γ=1.4). Final pressure? (Nearest integer)

Solution: 𝑃1𝑉1𝛾=𝑃2𝑉2𝛾

P1V1γ=P2V2γ.

𝑃2=2×(2/6)1.4≈0.76P2=2×(2/6)1.

4≈0.76 atm.  Answer: 1 (rounded).

Q4 (Jan Attempt - Carnot Efficiency): Carnot engine between 500 K and 300 K; efficiency?

Solution: η = 1 - (T_c/T_h) = 1 - 300/500 = 0.4 or 40%.

Q5 (Jan 2025 - Entropy Change): 1 mol ideal gas isothermal expansion from 10 L to 20 L at 300 K. ΔS?

Solution: ΔS = nR ln(V_f/V_i) = 1 × 8.314 × ln(2) ≈ 5.76 J/K.

Q6 (Jan Shift 1 - Work Done): Work by gas in isothermal expansion (1 mol, 300 K, 1L to 5L)?​

Solution: W = nRT ln(V_f/V_i) = 1×8.314×300×ln(5) ≈ 1240 J.

JEE Main April 2025 Questions

Q7 (April 2 Shift 1 - Processes): During the melting of an ice slab at 273 K (1 atm), identify the correct statement: (A) ΔH=0 (B) ΔS_system >0 (C) q_rev = ΔH (D)

Solution: Phase change at constant T: ΔH_fusion >0, ΔS = ΔH/T >0, reversible heat = ΔH. Answer: D.

Q8 (April 2025 - van der Waals Gas): Work done by van der Waals gas (isothermal, V1 to V2): Match options.youtube​

Solution: For real gas, W = ∫(P dV) using (P + a/V_m²)(V_m - b) = RT. Closest: nRT ln((V2-nb)/(V1-nb)) - a(1/V1 - 1/V2)/n.

Answer: A .

Q9 (April Session - Cyclic Process): For the cyclic process in an ideal gas, ΔU = ? (Options: Q=W, ΔU=0, etc.)

Solution: Cyclic: State function ΔU=0; Q=W. Answer: ΔU=0.

Q10 (April 2025 - Heat Engine): 5 mol N₂ in adiabatic vessel; heater 100 cal/s to N₂, 30 cal/s to 3 mol He piston. dT/dt for N₂?

Solution: For diatomic γ=1.4, C_v=5/2 R. Rate: (100-heat to He)/ (5R). Approx 0.8 K/s.

Answer: Option B.

Q11 (April Shift - Bond Enthalpy): Average O=O bond enthalpy from given reactions.youtube​

Solution: Use Hess's law: Balance H₂O₂ decomposition. Avg ≈ 498 kJ/mol. Answer: Nearest integer 498.

Q12 (April 2025 - Blackbody):

Blackbody radiation: Peak shifts to shorter λ as T↑?

Solution: Wien's law: λ_max T = constant. Answer: C.
Also Read: JEE Main Application Form 2025

Thermodynamics JEE Main Questions 2026 - Conceptual Questions

Add CollegeDekho as a Trusted Source

Candidates can check the questions along with their respective answers for the following sets of conceptual questions.

Q) Which of the following statements about an isothermal process is true?

A) The internal energy of the system remains constant.

B) The temperature of the system changes.

C) The work done by the system is zero.

D) The system does not exchange heat with the surroundings.

Answer : A

Q) Which law of thermodynamics states that the entropy of an isolated system always increases over time?

A) Zeroth Law

B) First Law

C) Second Law

D) Third Law

Answer : C

Q) For an ideal gas, which of the following expressions correctly describes the relationship between heat (Q), work (W), and change in internal energy (ΔU) in a cyclic process?

A) Q = W + ΔU

B) ΔU = W + Q

C) Q = ΔU

D) ΔU = 0

Answer : D

Q) The efficiency (η) of a heat engine is given by η = 1 - (T_c / T_h), where T_c is the temperature of the cold reservoir and T_h is the temperature of the hot reservoir. What type of process is this engine operating in?

A) Isothermal

B) Adiabatic

C) Isobaric

D) Isometric

Answer : A

Q) For an ideal gas undergoing an isothermal expansion, which of the following quantities remains constant?

A) Pressure

B) Volume

C) Temperature

D) Internal Energy

Answer : C

Q) In an adiabatic process, which of the following is true about the heat transfer?

A) Heat is absorbed by the system.

B) Heat is released by the system.

C) There is no heat transfer between the system and the surroundings.

D) The heat transfer is equal to the work done by the system.

Answer : C

Practice Questions for JEE Mains 2026

Candidates must solve the following practice questions for JEE Mains 2026.

Q 1) For an ideal gas undergoing an isobaric process, which of the following is true?

A) The pressure remains constant, and the volume changes.

B) The volume remains constant, and the temperature changes.

C) The temperature remains constant, and the pressure changes.

D) The internal energy remains constant.

Q 2) The change in enthalpy ΔH during a chemical reaction is equal to:

A) The heat absorbed or released at constant volume

B) The work done by the system

C) The heat absorbed or released at constant pressure

D) The change in internal energy minus the work done

Q 3) The first law of thermodynamics is a statement of the conservation of:

A) Energy

B) Momentum

C) Mass

D) Charge

Q 4) Which of the following statements is true for an isothermal process?

A) The temperature remains constant, and internal energy remains constant.

B) The temperature remains constant, and heat is transferred into or out of the system.

C) The volume remains constant, and work is done on or by the system.

D) The pressure remains constant, and the system is isolated.

Q 5) For an ideal gas, the internal energy depends only on:

A) Pressure

B) Volume

C) Temperature

D) Pressure and Volume

Q 6) The efficiency of a heat engine is given by

A) Heat Input / Work Output

B) Work Output / Heat Input

C) Heat Output / Heat Input

D) (Heat Input - Heat Output) / Heat Input

Related Reads

Candidates can check this article to solve Thermodynamics JEE Main Questions 2026 along with practising the conceptual and formula-based questions. Stay tuned to Collegedekho for the latest updates on JEE Mains 2026.

Are you feeling lost and unsure about what career path to take after completing 12th standard?

Say goodbye to confusion and hello to a bright future!

Take The Free Test Now

Was this article helpful?

0 Upvotes

0 Downvotes