CN  ChemNexa

Chemical Thermodynamics JEE Main MCQ & Practice Questions

Practice Chemical Thermodynamics MCQs for JEE Main Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

Register Free for Full Chemistry Practice

Chemical Thermodynamics Revision Guide for JEE Main Chemistry

Thermodynamics relates heat, work, internal energy, enthalpy and spontaneity. It is best learned through sign conventions and state-function logic rather than isolated memorisation.

For JEE Main Chemistry, revise the first law, enthalpy changes, Hess law, entropy and Gibbs free energy, then practise conceptual and numerical MCQs together.

Important Topics

  • System, surroundings and state functions
  • First law of thermodynamics
  • Enthalpy and heat capacity
  • Hess law
  • Entropy
  • Gibbs free energy and spontaneity

Important Formulae & Relationships

  • ΔU = q + w
  • At constant pressure: qp = ΔH
  • ΔH = ΔU + ΔngRT (for ideal-gas reactions)
  • ΔG = ΔH − TΔS
  • ΔG° = −RT ln K

Use formulas only after checking the required units, sign convention and assumptions for the question.

What to practise in Chemical Thermodynamics

Concept Revision

Revise definitions, principles, equations, trends and core ideas from Chemical Thermodynamics before attempting MCQs.

Exam-style MCQs

Use chapter-focused multiple-choice practice to improve accuracy, recall and application for JEE Main Chemistry.

Performance Practice

Attempt ChemNexa tests, review results and return to weak areas for another round of targeted revision.

Top 20 Chemical Thermodynamics MCQs with Answers

These public questions are selected from the exact Chemical Thermodynamics chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

1. Hess's law works because enthalpy is a

  • A. Kinetic quantity
  • B. State function
  • C. Path function
  • D. Vector
Answer: B
Explanation: Overall ΔH is path independent.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

2. At constant T,P, spontaneity requires

  • A. ΔG>0
  • B. ΔG=0 always
  • C. ΔH=0
  • D. ΔG<0
Answer: D
Explanation: Negative ΔG indicates spontaneous direction.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

3. First law of thermodynamics is

  • A. ΔU=q/w
  • B. ΔU=0 always
  • C. ΔU=q+w
  • D. ΔU=q-w always
Answer: C
Explanation: Using chemistry sign convention, ΔU=q+w.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

4. Standard enthalpy of formation of an element in standard state is

  • A. Zero
  • B. 1 kJ mol^-1
  • C. Always negative
  • D. Always positive
Answer: A
Explanation: By convention ΔHf°=0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

5. For spontaneous process in isolated system, entropy of universe

  • A. Decreases
  • B. Always zero
  • C. Becomes negative
  • D. Increases
Answer: D
Explanation: Second law gives ΔSuniv>0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

6. For spontaneous irreversible process, ΔSuniverse is

  • A. Undefined
  • B. Positive
  • C. Zero
  • D. Negative
Answer: B
Explanation: Irreversibility produces entropy.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

7. If ΔH<0 and ΔS>0, process is

  • A. Only high T
  • B. Only low T
  • C. Spontaneous at all temperatures
  • D. Never spontaneous
Answer: C
Explanation: Both terms favour ΔG<0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

8. If ΔH>0 and ΔS<0, process is

  • A. Only low T
  • B. Non-spontaneous at all temperatures
  • C. Always spontaneous
  • D. Only high T
Answer: B
Explanation: Both terms make ΔG>0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

9. If ΔH<0 and ΔS<0, spontaneity is favoured at

  • A. Low temperature
  • B. High temperature
  • C. All temperatures
  • D. No temperature
Answer: A
Explanation: At low T, negative ΔH can dominate.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

10. If ΔH>0 and ΔS>0, spontaneity is favoured at

  • A. Low temperature
  • B. All temperatures
  • C. No temperature
  • D. High temperature
Answer: D
Explanation: At high T, -TΔS can dominate.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

11. If ΔH=0 and ΔS>0, then at T>0

  • A. ΔG<0
  • B. ΔG>0
  • C. ΔG=0
  • D. Cannot decide
Answer: A
Explanation: ΔG=-TΔS<0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

12. If ΔS=0 and ΔH<0, then

  • A. ΔG>0
  • B. ΔG=0
  • C. Only high T spontaneous
  • D. ΔG<0 at all temperatures
Answer: D
Explanation: ΔG=ΔH<0.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

13. JEE Main advanced

  • A. ΔH=0
  • B. ΔG<0
  • C. ΔG>0
  • D. ΔG=0 always
Answer: B
Explanation: Negative ΔG indicates spontaneous direction.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

14. A state function depends on

  • A. Path
  • B. Time only
  • C. Rate
  • D. Initial and final states only
Answer: D
Explanation: State functions are path independent.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

15. Which is a path function?

  • A. Internal energy
  • B. Entropy
  • C. Heat
  • D. Enthalpy
Answer: C
Explanation: Heat depends on process path.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

16. Enthalpy is

  • A. H=U/PV
  • B. H=U+PV
  • C. H=U-PV
  • D. H=PV/U
Answer: B
Explanation: Definition of enthalpy is H=U+PV.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

17. At constant pressure, qp equals

  • A. ΔH
  • B. ΔU always
  • C. ΔS
  • D. ΔV
Answer: A
Explanation: For PV work, qp=ΔH.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

18. For an exothermic reaction, ΔH is

  • A. Zero
  • B. Infinite
  • C. Negative
  • D. Positive
Answer: C
Explanation: Exothermic reactions release heat.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

19. For an endothermic reaction, ΔH is

  • A. Undefined
  • B. Positive
  • C. Negative
  • D. Zero
Answer: B
Explanation: Endothermic reactions absorb heat.

JEE Main Chemistry · Chemical Thermodynamics · Very Very Hard

20. For an ideal gas, internal energy depends only on

  • A. Molar mass
  • B. Temperature
  • C. Pressure
  • D. Volume
Answer: B
Explanation: Ideal-gas U depends only on T.

Login to Start Full Test

Chemical Thermodynamics Practice Tests

Chemical Thermodynamics Frequently Asked Questions

What causes most Thermodynamics mistakes?

Sign conventions for heat and work, confusing state functions with path functions, and using inconsistent units are common sources of error.

What does negative ΔG indicate?

For a process under the stated conditions, negative Gibbs free-energy change indicates thermodynamic spontaneity.

How should I revise Thermodynamics?

Build a one-page sign-convention and formula sheet, then practise problems that require choosing the correct relation rather than only substituting numbers.

Continue with another chapter to build connected concepts and strengthen your overall Chemistry preparation.

Continue JEE Main Chemistry

View all JEE Main chapters and testsBrowse all Chemistry PracticeCreate a free account