IIT JEE Chemistry Practice Paper – Part 16 (Thermodynamics) with Formula Sheet
Instructions: Each question carries 4 marks. Select the correct answer and click Submit to view your score, correct answers, and explanations. Q1. The internal energy change (ΔU) for an isothermal process is: a) Positive b) Negative c) Zero d) Cannot be predicted Q2. The first law of thermodynamics is a statement of the law of conservation of: a) Mass b) Energy c) Momentum d) Entropy Q3. The enthalpy change (ΔH) and internal energy change (ΔU) are related by: a) ΔH = ΔU + ΔnRT b) ΔH = ΔU – ΔnRT c) ΔH = ΔU × ΔnRT d) ΔH = ΔU / ΔnRT Q4. The entropy of the universe in a spontaneous process: a) Decreases b) Increases c) Remains constant d) Becomes zero Q5. For an adiabatic process, which of the following is true? a) q = 0 b) ΔU = 0 c) w = 0 d) ΔH = 0 Q6. Which of the following thermodynamic quantities is a state function? a) Work b) Heat c) Internal Energy d) Both heat and work Q7. The Gibbs free energy change (ΔG) for a spontaneous process is: a) Positive b) Negative c) Zero d) Infinite Q8. Work done in an isothermal reversible expansion of an ideal gas is given by: a) w = nRT ln(V₂/V₁) b) w = –nRT ln(V₂/V₁) c) w = PΔV d) w = ΔU Q9. The condition for equilibrium in terms of Gibbs free energy is: a) ΔG > 0 b) ΔG = 0 c) ΔG < 0 d) ΔH = 0 Q10. Which of the following processes is endothermic? a) Condensation of steam b) Freezing of water c) Melting of ice d) Combustion of methane Submit IIT JEE Chemistry – Thermodynamics Summary & Formula Sheet Thermodynamics is the branch of physical chemistry that studies energy changes accompanying physical and chemical processes. It helps us understand the direction and feasibility of reactions — an essential part of IIT JEE Chemistry. 1. Basic Terms System: The part of the universe under study (e.g., reacting mixture). Surroundings: Everything outside the system. Types of Systems: Open – exchanges both matter and energy. Closed – exchanges energy but not matter. Isolated – exchanges neither energy nor matter. 2. Thermodynamic Processes Isothermal: Temperature constant (ΔT = 0). Adiabatic: No heat exchange (q = 0). Isobaric: Constant pressure. Isochoric: Constant volume. Reversible: Infinitely slow, equilibrium maintained. Irreversible: Rapid and spontaneous, not in equilibrium. 3. First Law of Thermodynamics Energy can neither be created nor destroyed; it can only be transformed. ΔU = q + w ΔU – Change in internal energy q – Heat absorbed by the system w – Work done on the system For ideal gas: w = –PextΔV At constant volume: qv = ΔU At constant pressure: qp = ΔH 4. Enthalpy (H) H = U + PV Change in enthalpy: ΔH = ΔU + PΔV For chemical reactions: ΔH = ΣHproducts – ΣHreactants Exothermic: ΔH < 0 Endothermic: ΔH > 0 5. Heat Capacities Cp – Cv = R For n moles of gas: ΔU = nCvΔT and ΔH = nCpΔT 6. Hess’s Law The total enthalpy change of a reaction is the same, irrespective of the path taken. ΔHoverall = ΣΔHindividual steps 7. Second Law of Thermodynamics The entropy (S) of an isolated system always increases in a spontaneous process. ΔSuniverse = ΔSsystem + ΔSsurroundings > 0 8. Gibbs Free Energy (G) G = H – TS Change in Gibbs energy: ΔG = ΔH – TΔS ΔG < 0 → Reaction is spontaneous ΔG = 0 → System at equilibrium ΔG > 0 → Non-spontaneous reaction 9. Key Relations ΔG° = –RT ln K (Relation between Gibbs energy and equilibrium constant) w = –nRT ln(V₂/V₁) (Reversible isothermal expansion of ideal gas) Conclusion Thermodynamics forms the backbone of physical chemistry, connecting energy, heat, and work with the spontaneity and equilibrium of reactions. By mastering concepts like internal energy (U), enthalpy (H), entropy (S), and Gibbs free energy (G), IIT JEE aspirants can predict the feasibility and direction of any chemical process — making it one of the most scoring topics in the exam.









