UPSC Combined Geo-Scientist, Mains · 2025 · Mains Paper II
Q15(b). Equispaced lines do not mean equispaced levels
Question
Spectral lines of the microwave spectrum of rigid diatomic molecules are equispaced. So energy levels are also equispaced. Justify or criticize with reasons.
Model answer
The free solution for 2025 answers questions 1, 2, 4, 5, 6, 7, 10, 11, 12 and 13, the ones picked in its time plan. Question 15 is answered in full in the Geo-Scientist Chemistry Paper II, 2021 to 2025 book, with every part of every paper.
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UPSC Combined Geo-Scientist (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All fifteen questions of each paper, with the question printed above its answer
- Numericals worked from formula to result with units; graphs with labelled axes
- Topic-wise weightage and a topic-wise index
Coversrigid rotorrotational energy levelsmicrowave spectrumselection rule ΔJ = ±1rotational constant
All parts of Question 15
- 15(a) Symmetric stretch of CO₂: IR inactive, Raman active5 marks
- 15(b) Equispaced lines do not mean equispaced levels5 marks
- 15(c) B, I and r₀ of H³⁵Cl from the line spacing10 marks