UPSC Civil Services (Mains)
Chemistry optional
- 2 papers
- 250 marks each
- 3 h per paper
- 5 of 8 questions, Q1 and Q5 compulsory
Paper I covers physical and inorganic chemistry.
All years
Pages 1 and 2 of 50 
Pages 3 and 4 of 50 
Pages 5 and 6 of 50 
Pages 7 and 8 of 50
Pages 9 and 10 of 50 Pages 11 and 12 of 50 Pages 13 and 14 of 50 Pages 15 and 16 of 50 Pages 17 and 18 of 50 Pages 19 and 20 of 50 Pages 21 and 22 of 50 Pages 23 and 24 of 50 Pages 25 and 26 of 50 Pages 27 and 28 of 50 Pages 29 and 30 of 50 Pages 31 and 32 of 50 Pages 33 and 34 of 50 Pages 35 and 36 of 50 Pages 37 and 38 of 50 Pages 39 and 40 of 50 Pages 41 and 42 of 50 Pages 43 and 44 of 50 Pages 45 and 46 of 50 Pages 47 and 48 of 50 Pages 49 and 50 of 50 
Paper I, physical and inorganic chemistry
Solution, 2023
UPSC Civil Services (Mains), Chemistry optional. 50 pages. All eight questions are answered.
Every question of 2023, one page each36 parts in 8 questions, with the question as text and the key points of its answer
Question 1 50 marks
- 1(a)Light emitted by a particle in a box; the uncertainty principle10 marks
- 1(b)Lewis structures of [Br₃]⁻ and thiourea; the most polar bond10 marks
- 1(c)Bragg equation and the layer spacing10 marks
- 1(d)Root-mean-square speed of water molecules10 marks
- 1(e)(i)E° of Cr³⁺/Cr from two couples5 marks
- 1(e)(ii)Surface tension, contact angle and loss of gravity5 marks
Question 2 50 marks
Question 3 50 marks
Question 4 50 marks
Question 5 50 marks
Question 6 50 marks
Question 7 50 marks
- 7(a)Haemoglobin and cytochrome c; oxy- and deoxyhaemoglobin10 marks
- 7(b)Configurations of Pr, Eu and Gd and the moments of their M³⁺ ions10 marks
- 7(c)Rate expression for a bimolecular surface reaction10 marks
- 7(d)Electronic spectrum of [Ni(OS(CH₃)₂)₆]²⁺10 marks
- 7(e)Reversible isothermal expansion of an ideal gas10 marks
Part of VKC Basic
Read the full model answer to every question of this paper with VKC Basic
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Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Printed copy and Kindle
UPSC Civil Services (Main) Chemistry Paper I: Model Answers 2021 to 2025
The book has all five years of Paper I in one volume, with every question printed above its answer, a time plan for each paper, the topic-wise weightage of marks and a topic-wise index.