UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper I covers inorganic chemistry.
Nuclear chemistry: every question, 2016 to 2025
39 parts worth 355 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.
Radioactive decay: general characteristics, decay kinetics, parent-daughter decay growth relationships, determination of half-lives. Nuclear stability. Decay theories. Unit of radioactivity. Preparation of artificial radionuclides by bombardment, radiochemical separation techniques. Experimental techniques in the assay of radioisotopes, Geiger-Muller counters. Solid state detectors.
Notes: Nuclear chemistry: decay, binding energy and the GM counter (full notes) · short notes
2025
- Q1(i) Complete the nuclear equations5 marks Answered
- Q4(c) Magic numbers; stability of ²⁰⁸₈₂Pb5 marks Answered
- Q5(c) Blood volume by ²⁴Na isotope dilution10 marks Question only
- Q9(a) Binding energy per nucleon; fusion and fission15 marks Answered
- Q11(a) Geiger–Müller counter: components and working15 marks Question only
2024
- Q1(i) Identifying radioactive decay5 marks Answered
- Q5(b) Balancing nuclear capture products10 marks Answered
- Q9(a) Carbon-14 activity in living carbon10 marks Answered
- Q9(b) Missing nuclear reaction partners5 marks Answered
- Q9(c) Separation and enrichment factors10 marks Answered
- Q9(d) Time for activity to fall5 marks Answered
2023
- Q1(h) Time for 74% radioactive material to remain5 marks Answered
- Q11(a) Packing fraction and binding energy of iron-5615 marks Question only
- Q11(b) Radiocarbon age of a wood sample10 marks Question only
- Q11(c) Balancing missing nuclear particles5 marks Question only
2022
- Q1(i) Carbon-14 dating of wood5 marks Answered
- Q10(a) Initial activity and first-second disintegrations15 marks Question only
- Q10(b) Completing nuclear decay equations5 marks Question only
- Q10(c) Geiger-Müller counter10 marks Question only
2021
- Q1(i) Balancing nuclear reactions5 marks Answered
- Q10(a) Thermal-neutron fission of uranium-2355 marks Question only
- Q10(b) Displacement law and four radioactive series15 marks Question only
- Q10(c) Alpha decay10 marks Question only
2020
- Q1(i) Iodine beta decay5 marks Answered
- Q10(a) Argon mass defect and packing fraction15 marks Answered
- Q10(c) Completing nuclear reactions5 marks Answered
2019
- Q1(b) Carbon isotopes and stability5 marks Answered
- Q8(a) Geiger–Müller counter and its limits for α and γ15 marks Question only
- Q8(b) Packing fraction versus mass number15 marks Question only
2018
- Q1(g) Radiocarbon age5 marks Answered
- Q8(a) Nuclear shell model15 marks Answered
- Q8(b) Binding-energy curve10 marks Answered
- Q8(c) Beta decay products5 marks Answered
2017
- Q1(e) Magic numbers5 marks Answered
- Q10(b) Nuclear stability and packing fraction10 marks Question only
2016
- Q1(g) Packing fraction5 marks Answered
- Q2(a) Liquid-drop model; why U-238 is an α-emitter15 marks Question only
- Q3(b) Mass defect and binding energy10 marks Answered
- Q11(b) Detection and measurement of nuclear radiations15 marks Question only
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