UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper III covers analytical and organic chemistry.
All topics
Mains Paper III, analytical and organic chemistry
X-ray methods of analysis: every question, 2016 to 2025
17 parts worth 155 marks have been set on this unit in UPSC Geo-Scientist Chemistry Mains Paper III from 2016 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
Syllabus
Introduction, theory of X-ray generation, X-ray spectroscopy, X-ray diffraction and X-ray fluorescence methods, instrumentation and applications. Qualitative and quantitative measurements. Powder diffraction method.
Notes: X-ray methods (XRD, XRF) and ICP-OES / ICP-MS (full notes) · short notes
2025
- Q1(h) Lattice spacing from Bragg’s law5 marks Answered
- Q5(a) Energy dispersive X-ray fluorescence: theory and instrument15 marks Question only
2024
- Q1(e) Properties needed in a detector for X-ray fluorescence5 marks Answered
- Q3(a) Qualitative phase analysis by X-ray powder diffraction10 marks Question only
- Q4(c) Detection of X-rays; types of X-ray detectors10 marks Answered
2023
- Q1(f) K and L lines in XRF; wavelength-dispersive spectrum of Zn5 marks Answered
- Q1(h) Type metal: constituents and non-destructive analysis5 marks Answered
- Q2(d) No K lines of silver at a tube voltage of 24 kV5 marks Question only
- Q4(a) Powder XRD: lattice type, cell edge and density15 marks Answered
2022
- Q1(f) X-rays from radioactive isotopes5 marks Answered
- Q3(a) Density of silver from its powder XRD pattern15 marks Question only
2021
- Q1(h) Powder X-ray diffraction for identifying solids5 marks Answered
- Q4(a) X-ray fluorescence: theoretical basis; bulk against surface15 marks Question only
2020
- Q1(e) Matrix effects in XRF5 marks Answered
2019
- Q5(a) Energy-dispersive XRF and matrix effects15 marks Question only
2017
- Q2(c) X-ray fluorescence10 marks Answered
- Q2(d) Orthorhombic unit cell10 marks Answered
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UPSC Combined Geo-Scientist (Main) Chemistry Paper III: Model Answers 2021 to 2025
- All ten questions of each paper, with the question printed above its answer
- Instruments drawn as labelled diagrams, numericals worked with units
- Topic-wise weightage and a topic-wise index