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
The gaseous state: every question, 2021 to 2025
6 parts worth 55 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
Equation of state for real gases, intermolecular interactions, liquefaction of gases and critical phenomena, Maxwell's distribution of speeds, intermolecular collisions, collisions on the wall and effusion.
Notes: Kinetic theory of gases: Maxwell distribution, collisions, mean free path, effusion and transport (full notes) · short notes
Notes: Real gases: van der Waals equation, critical constants, Boyle temperature (full notes) · short notes
2025
- Q3(b)(i) Composition after hydrogen leakage5 marks Answered
2024
- Q8(a) Equal mean speeds of oxygen and hydrogen10 marks Answered
- Q8(b) Critical compressibility of a van der Waals gas10 marks Answered
2023
- Q3(c) Ideal and van der Waals pressures10 marks Question only
2022
- Q4(a) Excluded volume of hard-sphere molecules10 marks Answered
2021
- Q3(a) Maximum low-pressure slope of Z10 marks Question only
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