Q8(c)(ii). Lanthanide moments and intense UV transitions
Among Ce³⁺, Eu³⁺, Tb³⁺ and Yb³⁺ ions, for which one is the calculated magnetic moment zero? Why? Among these ions, for which two ions are appreciably higher intensity bands found in the lower energy UV-region than the other two? Explain mentioning the transition.
Model answer
The free solution for 2023 answers questions 1, 2, 4, 5 and 6, the ones picked in its time plan. Question 8 is answered in full in the IFoS Chemistry Paper I, 2021 to 2025 book, with every part of every paper.
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UPSC Indian Forest Service (Main) Chemistry Paper I: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Physical chemistry numericals worked with units; inorganic structures drawn
- Topic-wise weightage and a topic-wise index
Coverslanthanide magnetic momentEu³⁺ ground term4f–5d transitioncharge-transfer bandslanthanide spectra
All parts of Question 8
- 8(a) Concerted and SN2 oxidative addition10 marks
- 8(b) Reactions in liquid ammonia15 marks
- 8(c)(i) Basicity of lanthanide hydroxides7 marks
- 8(c)(ii) Lanthanide moments and intense UV transitions8 marks