Q7(c). Why thick bottle glass looks coloured
Ordinary bottle glass appears nearly colourless when viewed through the wall of the bottle but visibly coloured (green) when viewed from the end so that light has a long path through the glass. The colour is associated with the presence of Fe³⁺ in the silicate matrix. Explain this observation.
Model answer
The free solution for 2024 answers questions 1, 2, 5, 6, 9 and 11, the ones picked in its time plan. Question 7 is answered in full in the Geo-Scientist Chemistry Paper I, 2021 to 2025 book, with every part of every paper.
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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
CoversBeer-Lambert lawFe3+ in glassspin-forbidden transitionspath length absorbanceglass colour
All parts of Question 7
- 7(a) Oxidative addition and reductive elimination10 marks
- 7(b)(i) Two forms of dicobalt octacarbonyl5 marks
- 7(b)(ii) Tetrahedral Ir₄(CO)₁₂5 marks
- 7(c) Why thick bottle glass looks coloured10 marks