UPSC Combined Geo-Scientist, Mains · 2025 · Mains Paper II
Q15(a). Symmetric stretch of CO₂: IR inactive, Raman active
Question
The symmetric stretching vibration of the linear CO₂ molecule is vibrational spectrum inactive but vibrational Raman spectrum active. Give reason(s).
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
CoversRaman spectroscopyIR selection rulepolarisabilitysymmetric stretch of CO2rule of mutual exclusion
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