UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper II covers physical chemistry.
Solids: every question, 2016 to 2025
29 parts worth 190 marks have been set on this unit in UPSC Geo-Scientist Chemistry Mains Paper II from 2016 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
Nature of solid state. Band theory of solids: qualitative idea of band theory, conducting, semiconducting and insulating properties. Law of constancy of angles, concept of unit cell, different crystal systems, Bravais lattices, law of rational indices, Miller indices, symmetry elements in crystals. X-ray diffraction, Bragg's law.
Notes: Defects in solids, non-stoichiometry and semiconductors (full notes) · short notes
Notes: Crystal systems, Miller indices, Bragg's law and radius ratio (full notes) · short notes
2025
- Q1(c) Band structure of n-type and p-type semiconductors5 marks Answered
- Q1(d) Symmetry elements of orthorhombic Mg₂SiO₄5 marks Answered
- Q3 Limits of powder XRD: Co–Ni alloy and sub-micron crystallites10 marks Question only
2024
- Q1(c) Conductors, semiconductors and insulators: band picture5 marks Answered
- Q1(d) Cubic and tetragonal Bravais lattices5 marks Answered
- Q3(a) Miller indices of the plane (2a, −3b, −3c)3 marks Answered
- Q3(b) Atomic mass of a bcc element from density and cell edge7 marks Answered
- Q13(a) Unit cell of HgCl₂ from three Bragg reflections10 marks Answered
2023
- Q1(c) Unit cell of solid C₆₀ and its carbon atoms5 marks Answered
- Q1(d) Planes that diffract: simple cubic, a = 5 Å5 marks Answered
- Q3 Orthorhombic cell: Bravais lattice and d₂₂₂10 marks Answered
- Q11(b) Cell edge of silicon from its density10 marks Answered
2022
- Q1(c) Temperature coefficient of conductivity: metal and semiconductor5 marks Answered
- Q1(d) Why KCl diffracts like a simple cubic lattice5 marks Answered
- Q3 Compactness of simple cubic, bcc and fcc crystals10 marks Answered
- Q11(b) Number of unit cells in 100 g of a cubic metal10 marks Question only
2021
- Q1(c) Formula from corner and face-centre positions5 marks Answered
- Q1(d) Crystal systems from the unit-cell constants5 marks Answered
- Q3 Lattice type from first-order Bragg reflections10 marks Answered
- Q11(b) Ionic, covalent, molecular and metallic crystals5 marks Question only
2020
- Q1(c) Accuracy at high diffraction angle5 marks Answered
- Q3 Formula units in rock-salt KCl10 marks Answered
2019
- Q1(d) Atoms in a BCC sample5 marks Answered
- Q3(a) Silver diffraction angles5 marks Answered
2018
- Q1(d) FCC particle count5 marks Answered
- Q8(a) BCC interplanar spacing5 marks Answered
2017
- Q10(a) First-order Bragg angle for Ag (111)5 marks Question only
2016
- Q1(c) Entropy and diffraction5 marks Answered
- Q4 Orthorhombic crystal: interplanar spacing d(hkl)10 marks Question only
UPSC Combined Geo-Scientist (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All fifteen questions of each paper, with the question printed above its answer
- Numericals worked from formula to result with units; graphs with labelled axes
- Topic-wise weightage and a topic-wise index