UPSC Civil Services (Mains)
Chemistry optional
- 2 papers
- 250 marks each
- 3 h per paper
- 5 of 8 questions, Q1 and Q5 compulsory
Paper I covers physical and inorganic chemistry.
All topics
Paper I, physical and inorganic chemistry
Surface phenomena and catalysis: every question, 2021 to 2025
9 parts worth 100 marks have been set on this unit in UPSC CSE 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
Adsorption from gases and solutions on solid adsorbents; Langmuir and B.E.T. adsorption isotherms; determination of surface area, characteristics and mechanism of reaction on heterogeneous catalysts.
Notes: Adsorption, heterogeneous catalysis and colloids (full notes) · short notes
2025
- Q5(c) Surface area of charcoal from a nitrogen monolayer5 marks Answered
- Q6(c) Langmuir adsorption isotherm20 marks Answered
2024
- Q5(b)(i) How water condenses onto glass5 marks Answered
- Q5(b)(ii) Time to form half a monolayer at 2.0 × 10⁻¹¹ torr5 marks Answered
- Q6(b) Heterogeneous catalysis; PH₃ on tungsten15 marks Answered
2023
- Q7(c) Rate expression for a bimolecular surface reaction10 marks Answered
2022
- Q7(d) Surface area of an adsorbent from the nitrogen monolayer10 marks Answered
- Q8(e) Langmuir isotherm and the kinetics of surface reactions10 marks Answered
2021
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UPSC Civil Services (Main) Chemistry Paper I: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Question choice and time plan for each paper
- Topic-wise weightage and a topic-wise index