UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper II covers physical chemistry.
All years
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Mains Paper II, physical chemistry
Solution, 2026
UPSC Combined Geo-Scientist, Stage II (Mains). 22 pages. Questions 1, 2, 3, 5, 8, 9, 10, 13, 14 and 15 are answered.
Every question of 2026, one page each35 parts in 15 questions, with the question as text and the key points of its answer
Question 1 80 marks
- 1(a)Compressibility factor and its significance5 marks
- 1(b)Andrew's isotherms and the critical-point conditions5 marks
- 1(c)First-order Bragg angle for the (110) planes5 marks
- 1(d)Intrinsic semiconductor and its conversion to extrinsic5 marks
- 1(e)Fugacity against pressure of a non-ideal gas5 marks
- 1(f)Kₚ and K_c for A+B⇌ C5 marks
- 1(g)Half-life of a nuclide with two parallel first-order decays5 marks
- 1(h)Soap and detergent5 marks
- 1(i)Galvanic cell for 2 Cu⁺leftharpoonsCu²⁺+Cu5 marks
- 1(j)pH when a weak base is 65% neutralised5 marks
- 1(k)Uncertainty in an energy eigenstate5 marks
- 1(l)Expectation value and eigenvalue5 marks
- 1(m)Normal modes of vibration5 marks
- 1(n)Raman activity and polarisability ellipsoids of CO₂5 marks
- 1(o)The incorrect statement on electronic spectra5 marks
- 1(p)Non-radiative decay competing with fluorescence5 marks
Question 2 10 marks
Question 3 10 marks
Question 4 10 marks
Question 5 10 marks
Question 6 10 marks
Question 7 10 marks
Question 8 10 marks
Question 9 10 marks
Question 10 10 marks
Question 11 20 marks
Question 12 20 marks
Question 13 20 marks
Question 14 20 marks