Q7(c)(i). Lanthanide oxidation states
What is the common oxidation state of lanthanides? Name two lanthanides which can exist in an oxidation state lower than the common one. What is this oxidation state? Name one lanthanide which can exist in a higher oxidation state than the common one. What is this oxidation state? Give an explanation for the existence of these uncommon oxidation states in each case.
Model answer
The free solution for 2022 answers questions 1, 2, 4, 5 and 6, the ones picked in its time plan. Question 7 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 oxidation statesEu2+ and Yb2+Ce4+f-block stabilityhalf-filled f shell
All parts of Question 7
- 7(a) Adsorption isotherms and BET theory10 marks
- 7(b)(i) Square-planar substitution and trans effect10 marks
- 7(b)(ii) Fluxional molecules and variable-temperature NMR5 marks
- 7(c)(i) Lanthanide oxidation states8 marks
- 7(c)(ii) Sharp weak f–f spectra7 marks