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
Liquid state: every question, 2021 to 2025
9 parts worth 75 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
Kelvin equation; surface tension and surface energy, wetting and contact angle, interfacial tension and capillary action.
Notes: Liquid state: surface tension, Kelvin equation, capillary action, viscosity and liquid crystals (full notes) · short notes
2025
- Q1(e) Superheating of liquids and the Kelvin equation5 marks Answered
- Q3(b) Droplets made from one mole of water15 marks Answered
2024
- Q3(b)(i) Surface tension: ethanol or dimethyl ether5 marks Answered
- Q3(b)(ii) Pressure difference across a water droplet of radius 150 nm5 marks Answered
2023
- Q1(e)(ii) Surface tension, contact angle and loss of gravity5 marks Answered
- Q4(b) Pressure difference needed to drink through a tilted straw10 marks Answered
- Q4(c) Diameter of a capillary from the pressure needed to blow a bubble10 marks Answered
2022
- Q4(c) Capillary rise of two liquids in the same tube10 marks Answered
2021
- Q3(a) Surface energy when one drop is split into 125 drops10 marks Answered
Printed copy and Kindle
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