UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper I covers inorganic chemistry.
Redox titrations: every question, 2016 to 2025
35 parts worth 320 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.
Standard redox potentials, Nernst equation. Influence of complex formation, precipitation and change of pH on redox potentials, Normal Hydrogen Electrode (NHE). Feasibility of a redox titration, redox potential at the equivalence point, redox indicators. Redox potentials and their applications. Principles behind iodometry, permanganometry, dichrometry, difference between iodometry and iodimetry. Principles of estimation of iron, copper, manganese, chromium by redox titration.
Notes: Redox titrations: equivalence potential, indicators, iodometry (full notes) · short notes
2025
- Q1(f) Colour change interval of diphenylamine5 marks Answered
- Q6(b) Equivalence-point potential: Fe²⁺ with dichromate at pH 115 marks Answered
- Q7(c) Oxidation of iron(II) by chlorine10 marks Question only
- Q8(a) Redox indicators; ferroin15 marks Question only
2024
- Q1(e) Spontaneity of Fe²⁺ oxidation5 marks Answered
- Q8(a) Completing useful redox equations15 marks Question only
- Q8(b) Ordering reducing strength5 marks Question only
- Q8(c) Redox-indicator transition potential10 marks Question only
2023
- Q1(f) Iodometry versus iodimetry5 marks Answered
- Q7(a) Mohr’s salt from a permanganate titre10 marks Answered
- Q7(b) Zimmermann-Reinhardt preventive solution15 marks Answered
- Q7(c) Products of permanganate reduction5 marks Answered
2022
- Q1(f) Iron percentage by permanganate5 marks Answered
- Q7(a) Permanganate potential at pH 310 marks Answered
- Q7(b) Iodine titrations and starch10 marks Answered
- Q7(c) Will silver nitrate dissolve all the copper?10 marks Answered
2021
- Q1(f) Role of mercuric chloride in iron titration5 marks Answered
- Q7(a) Types of redox titration15 marks Question only
- Q7(b) Practical conditions in iodine and permanganate titrations15 marks Question only
2020
- Q1(e) Iodometry and iodimetry5 marks Answered
- Q6(c) Zimmermann–Reinhardt solution in Fe²⁺–KMnO₄ titration10 marks Question only
- Q7(a) Cerimetric titration of iron15 marks Answered
- Q7(b) Nickel–cobalt displacement15 marks Answered
2019
- Q1(a) Permanganate and iron(II)5 marks Answered
- Q2(b) Equilibrium constant from cell potential10 marks Answered
- Q3(c) Copper wire in silver nitrate solution5 marks Question only
2018
- Q1(e) Halogen displacement5 marks Answered
- Q5(b) Premature end point in Fe²⁺–dichromate titration10 marks Question only
- Q6(c) Iron–hydrogen cell10 marks Answered
2017
- Q1(a) Dichromate oxidation of iron5 marks Answered
- Q2(c) Iodimetry and iodometry10 marks Answered
2016
- Q1(e) Interpreting the redox data5 marks Answered
- Q9(b) Dichromate half-reaction7 marks Answered
- Q9(c) Oxidation of iodide by dichromate8 marks Answered
- Q10(c) Iodometric determination of copper10 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