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
General chemistry of 'f' block elements: every question, 2021 to 2025
11 parts worth 115 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
Lanthanides and actinides; separation, oxidation states, magnetic and spectral properties; lanthanide contraction.
Notes: Lanthanides and actinides: contraction, magnetism, spectra, separation (full notes) · short notes
2025
- Q5(h) Magnetic moment: spin only in the d-block, not in the f-block5 marks Answered
- Q8(c) Lanthanides separated by change of valency10 marks Answered
- Q8(d) Magnetic moments of Pr³⁺ and Tb³⁺10 marks Answered
2024
- Q5(e)(i) Lanthanide contraction5 marks Answered
- Q5(e)(ii) Why Hf is placed below Zr5 marks Answered
- Q8(c) Principles of four methods of separating the lanthanides20 marks Answered
2023
- Q5(d) Electronic transitions in the spectra of actinide ions10 marks Answered
- Q7(b) Configurations of Pr, Eu and Gd and the moments of their M³⁺ ions10 marks Answered
2022
- Q6(b) Pale colours and line-like spectra of lanthanide ions10 marks Answered
- Q7(b) Aqueous LaCl₃ and LuCl₃: which is more acidic10 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