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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper I covers physical and inorganic chemistry.

All topics
Paper I, physical and inorganic chemistry

Thermodynamics and statistical thermodynamics: every question, 2021 to 2025

17 parts worth 163 marks have been set on this unit in UPSC IFoS Chemistry Paper I from 2021 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.

Syllabus

Thermodynamic systems, states and processes, work, heat and internal energy; first law of thermodynamics, work done on the systems and heat absorbed in different types of processes; calorimetry, energy and enthalpy changes in various processes and their temperature dependence. Second law of thermodynamics; entropy as a state function, entropy changes in various processes, entropy–reversibility and irreversibility, free energy functions; criteria for equilibrium, relation between equilibrium constant and thermodynamic quantities; Nernst heat theorem and third law of thermodynamics. Micro and macro states; canonical ensemble and canonical partition function; electronic, rotational and vibrational partition functions and thermodynamic quantities; chemical equilibrium in ideal gas reactions.

  • 17 parts
  • 163 marks
  • Marks by year:
  • 2025: 36
  • 2024: 28
  • 2023: 28
  • 2022: 38
  • 2021: 33
Cover of UPSC Indian Forest Service (Main) Chemistry Paper I: Model Answers 2021 to 2025
Printed copy and Kindle

UPSC Indian Forest Service (Main) Chemistry Paper I: Model Answers 2021 to 2025

  • All eight questions of each paper, with the question printed above its answer
  • Physical chemistry numericals worked with units; inorganic structures drawn
  • Topic-wise weightage and a topic-wise index