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.
Paper I, physical and inorganic chemistry
Blog
Strategy, answer writing, toppers' suggestions, booklists and video links for this paper.
Crystal field theory: why [CoF₆]³⁻ is paramagnetic but [Co(CN)₆]³⁻ is diamagnetic
Asked in 14 of 15 papers from 2021 to 2025 across CSE, Geo-Scientist and IFoS: book source, keyword map and a two-page model answer.
Particle in a box: probability in part of the box
Asked in CSE 2025, CSE 2022 and Geo-Scientist 2021: book source, keyword map and a three-page model answer.
How the Chemistry optional paper is built
Eight questions, five to attempt, and about 0.7 minutes for every mark.
Choosing three questions in the first ten minutes
Two questions are fixed. The other three decide whether you finish the paper.