UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper I covers inorganic chemistry.
Inorganic solids: every question, 2016 to 2025
33 parts worth 265 marks have been set on this unit in UPSC Geo-Scientist Chemistry Mains Paper I from 2016 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
Defects, non-stoichiometric compounds and solid solutions, atom and ion diffusion, solid electrolytes. Synthesis of materials, monoxides of 3d-metals, higher oxides, complex oxides (corundum, ReO₃, spinel, perovskites), framework structures (phosphates, aluminophosphates, silicates, zeolites), nitrides and fluorides, chalcogenides, intercalation chemistry, semiconductors, molecular materials.
Notes: Defects in solids, non-stoichiometry and semiconductors (full notes) · short notes
Notes: Inorganic solids: perovskite, spinel, ReO₃, corundum and high-Tc superconductors (full notes) · short notes
Notes: Main group chemistry: boranes, borazine, phosphazenes, silicates, silicones, interhalogens, xenon and S–N compounds (full notes) · short notes
2025
- Q1(a) Defect in silver chloride5 marks Answered
- Q2(a) Local ion displacement in BaTiO₃; electrical behaviour15 marks Question only
- Q2(b) Structures of non-stoichiometric hydrides and oxides10 marks Question only
- Q2(c) Synthesis of YBa₂Cu₃O₇5 marks Question only
2024
- Q1(a) Minerals and their compositions5 marks Answered
- Q2(a)(i) Fluorite and antifluorite5 marks Answered
- Q2(a)(ii) Schottky and Frenkel defects5 marks Answered
- Q2(a)(iii) Normal and inverse spinels5 marks Answered
- Q2(c) Polymorphism in crystals5 marks Answered
- Q4(c) Number of ions in an FeO unit cell10 marks Question only
2023
- Q1(a) Crystal structures and a point defect5 marks Answered
- Q3(a) Normal and inverse spinels15 marks Answered
- Q3(b) Composition of non-stoichiometric wustite10 marks Answered
- Q3(c) Point defects in crystals5 marks Answered
2022
- Q1(a) Minerals and framework structures5 marks Answered
- Q2(a) Two perovskite unit-cell origins10 marks Answered
- Q2(b) Increasing silicon conductivity10 marks Answered
- Q2(c) Fullerite basis and ammonolysis4 marks Answered
- Q2(d) Defects and solid-state properties6 marks Answered
2021
- Q1(a) Quartz-type aluminophosphate5 marks Answered
- Q2(a) ReO₃ unit cell and perovskite relation10 marks Answered
- Q2(b) Doping gallium arsenide10 marks Answered
- Q2(c)(i) Metal deficiency in wüstite5 marks Answered
- Q2(c)(ii) Solid-state and solution synthesis5 marks Answered
2020
- Q1(a) Normal and inverse spinels5 marks Answered
- Q2(b) Defects in CaCl₂ and AgBr10 marks Question only
- Q2(c) Non-stoichiometric defects in transition metal compounds5 marks Question only
2019
- Q1(i) Temperature and conductivity5 marks Answered
- Q10(c) Silicate units and pyro-, cyclic and chain silicates15 marks Question only
2018
- Q7(a) Band theory: conductors, semiconductors and insulators15 marks Question only
- Q10(b) Ortho-, pyro-, cyclic and chain silicates15 marks Question only
2017
- Q1(b) Phosphorus-doped silicon5 marks Answered
2016
- Q9(a) Classification of silicates15 marks Answered
UPSC Combined Geo-Scientist (Main) Chemistry Paper I: Model Answers 2021 to 2025
- All eleven questions of each paper, with the question printed above its answer
- Titration, gravimetric and nuclear numericals worked with units; structures drawn
- Topic-wise weightage and a topic-wise index