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Chemical Thermodynamics - WBJEE Practice & MCQs

Revision and practice for the Chemical Thermodynamics chapter for WBJEE. Topic-wise MCQs with answers, explanations and quick notes to strengthen core concepts.

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Chemical Thermodynamics Revision Guide for WBJEE 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 WBJEE 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 WBJEE Chemistry.

Performance Practice

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

Top 19 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.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

1. The first law of thermodynamics is mathematically expressed as

  • A. ΔU = q/w
  • B. ΔU = 0 for every process
  • C. ΔU = q + w
  • D. ΔU = q - w always
Answer: C
Explanation: Using the chemistry sign convention, change in internal energy equals heat supplied plus work done on the system.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

2. Gibbs free energy is defined as

  • A. G = U + TS
  • B. G = PV - TS
  • C. G = H - TS
  • D. G = H + TS
Answer: C
Explanation: Gibbs energy combines enthalpy and entropy contributions.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

3. At constant temperature and pressure, a process is spontaneous when

  • A. ΔH must be zero
  • B. ΔG < 0
  • C. ΔG > 0
  • D. ΔG = +∞
Answer: B
Explanation: Negative Gibbs energy change indicates spontaneous direction at constant T,P.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

4. Energetics concept check

  • A. G = H - TS
  • B. G = H + TS
  • C. G = U + TS
  • D. G = PV - TS
Answer: A
Explanation: Gibbs energy combines enthalpy and entropy contributions.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

5. WBJEE advanced

  • A. G = U + TS
  • B. G = PV - TS
  • C. G = H - TS
  • D. G = H + TS
Answer: C
Explanation: Gibbs energy combines enthalpy and entropy contributions.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

6. At constant pressure, heat absorbed by a system equals its change in

  • A. Enthalpy
  • B. Entropy only
  • C. Helmholtz energy
  • D. Volume
Answer: A
Explanation: For pressure-volume work only, qp = ΔH.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

7. Enthalpy is defined by

  • A. H = U - PV
  • B. H = PV/U
  • C. H = U/PV
  • D. H = U + PV
Answer: D
Explanation: Enthalpy is the state function H=U+PV.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

8. For an exothermic reaction at constant pressure, ΔH is

  • A. Zero always
  • B. Infinite
  • C. Negative
  • D. Positive
Answer: C
Explanation: An exothermic process releases heat, so products have lower enthalpy.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

9. For an endothermic reaction at constant pressure, ΔH is

  • A. Undefined
  • B. Positive
  • C. Negative
  • D. Zero always
Answer: B
Explanation: Heat absorption gives positive enthalpy change.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

10. Hess's law follows from the fact that enthalpy is a

  • A. State function
  • B. Path function
  • C. Vector quantity
  • D. Kinetic parameter
Answer: A
Explanation: The enthalpy change depends only on initial and final states.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

11. Standard enthalpy of formation of an element in its standard state is

  • A. One kJ mol^-1
  • B. Always negative
  • C. Always positive
  • D. Zero
Answer: D
Explanation: By convention, ΔHf° of an element in its reference state is zero.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

12. For a spontaneous process in an isolated system, total entropy tends to

  • A. Decrease
  • B. Remain zero always
  • C. Become negative
  • D. Increase
Answer: D
Explanation: The second law requires ΔS_universe > 0 for a spontaneous irreversible process.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

13. If K is much greater than 1, ΔG° is generally

  • A. Zero necessarily
  • B. Infinite positive
  • C. Negative
  • D. Positive
Answer: C
Explanation: ln K is positive, so -RT ln K is negative.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

14. A catalyst affects ΔH of a reaction by

  • A. Always making it positive
  • B. Not changing it
  • C. Making it zero
  • D. Always making it negative
Answer: B
Explanation: Reaction enthalpy is a state-function difference independent of pathway.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

15. Bond dissociation enthalpy is the enthalpy needed to

  • A. Condense a gas
  • B. Freeze a liquid
  • C. Break a specified bond in gaseous species
  • D. Form an ionic lattice
Answer: C
Explanation: Bond dissociation enthalpy refers to gas-phase bond cleavage.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

16. Using average bond enthalpies, reaction enthalpy is approximated by

  • A. Product of bond enthalpies
  • B. Σ bonds broken - Σ bonds formed
  • C. Σ bonds formed - Σ bonds broken
  • D. Σ all bonds
Answer: B
Explanation: Energy is absorbed in bond breaking and released in bond formation.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

17. Entropy is a thermodynamic measure associated with

  • A. Energy dispersal and number of accessible microstates
  • B. Atomic number
  • C. Reaction rate only
  • D. Molar mass only
Answer: A
Explanation: Entropy reflects the multiplicity and dispersal of energy.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

18. At equilibrium at constant T and P

  • A. ΔG = 0
  • B. ΔG < 0
  • C. ΔG > 0
  • D. ΔH = 0 necessarily
Answer: A
Explanation: There is no net driving force at equilibrium.

WBJEE Chemistry · Chemical Thermodynamics · Very Very Hard

19. The relation between standard Gibbs energy and equilibrium constant is

  • A. ΔG° = RT ln K
  • B. ΔG° = -KRT
  • C. ΔG° = RT/K
  • D. ΔG° = -RT ln K
Answer: D
Explanation: Standard Gibbs energy determines the equilibrium constant.

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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.

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