NCERT Exemplar Solutions Class 11 Chemistry Chapter 5 Thermodynamics PDF

NCERT Exemplar Solutions for Class 11 Chemistry Chapter 5 Thermodynamics solve all 62 questions from the Exemplar book. Every MCQ, Short Answer, Matching, Assertion and Reason and Long Answer problem is solved step by step in the free 240-page PDF, updated for the 2026-27 syllabus.

One detail confuses students before they even start. This chapter is Unit 6 in the printed Exemplar, not Unit 5, because the new edition dropped States of Matter. So the figures inside are labelled Fig. 6.1 onward. With 62 questions, this is the biggest chapter in the book.

• CBSE Weightage: 6 to 8 marks, usually one Hess's law numerical and one spontaneity reasoning question
• JEE Main Weightage: 2 to 3 questions per year, mostly first law, work and Gibbs energy
• NEET Weightage: 1 to 2 questions per year from enthalpy and entropy change

Every solution is checked against the official NCERT Exemplar key, and the three answer-key errors in this chapter are worked out in full.

Topics Covered in the Class 11 Chemistry Thermodynamics Exemplar

The 62 questions rest on four ideas that build in order. Each one feeds Equilibrium and the electrochemistry you meet in Class 12, so nothing here is spent effort.

• Systems and state functions: open, closed and isolated systems, and why enthalpy is a state function while heat is not
• The first law: ΔU = q + w, pressure-volume work, and reversible against irreversible paths
• Thermochemistry: enthalpy, heat capacity, Hess's law, bond and lattice enthalpy, and the Born-Haber cycle
• Spontaneity: entropy, Gibbs energy, and the link between ΔG and the equilibrium constant

Question Types in the Thermodynamics NCERT Exemplar

Six question types appear in this chapter. The Short Answer set alone holds 31 questions, which is half the chapter, and that is where the reasoning marks live.

Three Answer Key Errors in the Thermodynamics Exemplar

The printed key slips three times in this chapter. Each one is worked out in the PDF, so you are never asked to accept arithmetic that does not add up.

• Question 23: the key prints Δ_rH = +91.8 kJ mol^-1. That value fits decomposing one mole of ammonia, but the printed equation starts from 2NH₃, so every term doubles. The correct answer is +183.6 kJ mol^-1. The key flipped the sign without scaling for the coefficient.
• Question 40: the key writes C_p − C_v = nR = 10 × 4.184 J. The relation is right, but 4.184 is the joules-per-calorie factor, not R. Since R = 8.314 J K^-1 mol^-1, the answer is 83.14 J K^-1, not 41.84 J.
• Question 51: the key maps intensive property to heat. Heat is not an intensive property, and it is not a property at all. The same key calls it a path function two lines earlier, and nothing can be both.

Write the key's answer in the exam, then add one line explaining the slip. The marking scheme follows the printed key, so our solution gives the key's response first and then shows the correct physics.

Common Mistakes Students Make in Thermodynamics

The Exemplar plants wrong options on purpose here. These four catch most students, and each is flagged in the PDF at the question where it bites.

• Sign convention: in ΔU = q + w, work done on the system is positive. Reporting the work done by a gas as a negative number is the single most common slip in the Short Answer set.
• External pressure, never gas pressure: the work formula is w = −p_extΔV. Question 7 turns on this. In free expansion p_ext = 0, so w = 0, which forces q = 0, ΔT = 0 and w = 0 together.
• Exothermic does not mean spontaneous: a negative ΔH helps, but only ΔG decides. An endothermic change with a large positive ΔS still runs on its own.
• Coefficients in thermochemical equations: doubling a reaction doubles its ΔH. Question 23 exists to catch students who reverse but forget to scale.

How the Exemplar Steps Up from the Class 11 Chemistry Textbook

The textbook gives you a formula and asks you to substitute. The Exemplar asks you to decide which formula applies, and often to explain why the obvious one does not.

Question 9 shows this well. Water freezes in a beaker, and the entropy of the water clearly drops as a disordered liquid becomes an ordered crystal. Most students stop there and pick a wrong option. Freezing is exothermic, so the heat released raises the entropy of the surroundings. You have to run two entropy calculations, not one. No textbook question makes that split do real work.

How to Use These NCERT Exemplar Solutions for Boards, NEET and JEE

Attempt each question before you open the solution. The Exemplar repays the attempt far more than the reading.

• Boards: the 31 Short Answer questions match the 2 and 3 mark board pattern almost exactly
• NEET: work the 14 MCQ I questions first, since NEET repeats enthalpy and entropy at that level
• JEE Main: the MCQ II and Long Answer sets are the closest NCERT practice for multi-step Hess's law work

Student Feedback

Students using Collegedunia's Class 11 Chemistry Exemplar Solutions told us the sign conventions were the hardest part of this chapter. Around 7 in 10 said that seeing the three key errors explained, rather than glossed over, was what finally made them trust their own working.

Other Resources for Class 11 Chemistry Thermodynamics

Collegedunia has the full set of study material for this chapter. Use the Notes for a first read, then the Exemplar once the first law is steady.

Also Check:

• NCERT Solutions for Class 11 Chemistry Chapter 5
• Class 11 Chemistry Chapter 5 Notes
• Class 11 Chemistry Chapter 5 NCERT Book PDF
• Class 11 Chemistry Chapter 5 Exemplar Questions with Solutions

NCERT Exemplar Solutions for Other Class 11 Chemistry Chapters

Each chapter below has the same step-by-step treatment and a free PDF.