Q11(c). Pale pink octahedral and intense blue tetrahedral Co²⁺
Many octahedral complexes of Co²⁺ are pale pink in colour, while tetrahedral complexes of Co²⁺ are intensely blue in colour. Why?
Model answer
The free solution for 2025 answers questions 1, 3, 4, 6, 9 and 10, the ones picked in its time plan. Question 11 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
Topic notes: crystal field theory, with every Civil Services, IFoS and Geo-Scientist PYQ →
CoversLaporte selection ruletetrahedral vs octahedral cobalt(II)d-d transitionsCoCl4 2- bluemolar absorptivity
All parts of Question 11
- 11(a) Geiger–Müller counter: components and working15 marks
- 11(b) cis- and trans-[PtCl₂(NH₃)₂] with thiourea5 marks
- 11(c) Pale pink octahedral and intense blue tetrahedral Co²⁺10 marks