Indian Forest Service (Mains), Chemistry optional · 2025 · Paper I

Q8(b)(i). Lanthanide separation by valence change

5 marks
Topic: General chemistry of 'f' block elements
Question only

Question

Explain separation of lanthanides by changing their oxidation states.

Model answer

The free solution for 2025 answers questions 1, 2, 3, 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.

Read the 2025 solution

Part of VKC Basic

Read the key points and the full model answer with VKC Basic

VKC Basic (₹999 for 6 months) opens every solved answer, the notes, the handbook and the daily answer archive. Every Mains test series includes it.

See what is included Already a member? Sign in

Printed copy and Kindle

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

Printed copy Kindle edition Read sample pages

Topic notes: lanthanides and actinides (lanthanide contraction, magnetic moments, separation), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversseparation of lanthanidesCe(IV) oxidationEu(II) reductionoxidation states of lanthanides

All parts of Question 8

8(a)(i) Alkyne–dicobalt bonding10 marks
8(a)(ii) Alkene insertion into metal bonds5 marks
8(b)(i) Lanthanide separation by valence change5 marks
8(b)(ii) Similarity of second and third transition series10 marks
8(c)(i) Conductance of metal–ammonia solutions5 marks
8(c)(ii) Blue colour in liquid ammonia5 marks