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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumCalculation

JEE Main 24 February 2021, Shift 2, Chemistry Q40

Question 40 of 90 in this shift, Chemistry question 10 of 30, Section A.

The calculated magnetic moments (spin only value) for species [FeCl4]2−\mathrm{[FeCl_4]^{2-}}, [Co(C2O4)3]3−\mathrm{[Co(C_2O_4)_3]^{3-}} and MnO42−\mathrm{MnO_4^{2-}} respectively are :
  1. (1)4.90, 0 and 1.73 BMOfficial answer
  2. (2)5.92, 4.90 and 0 BM
  3. (3)5.82, 0 and 0 BM
  4. (4)4.90, 0 and 2.83 BM

Official answer

Option 1

NTA final key.

Chapter
Coordination Compounds
Topic
Crystal Field Theory
Idea tested
Spin-only Magnetic Moment

Same idea in other shifts

Asked 28× in all
  1. 4 Apr 2026, Shift 1 · Q62Match the LIST-I with LIST-II List-I (Complex ion): A. [Cr(H2O)6]2+[\mathrm{Cr(H_2O)_6}]^{2+}; B. [Co(H2O)6]2+[\mathrm{Co(H_2O)_6}]^{2+}; C.…EasyMatch the list
  2. 8 Apr 2025, Shift 2 · Q60Match the LIST-I with LIST-II LIST-I (Complex/ Species) | LIST-II (Shape & magnetic moment) A. [Ni(CO)4]\mathrm{[Ni(CO)_4]} | I. Tetrahedral, 2.8…MediumMatch the list
  3. 5 Apr 2024, Shift 1 · Q71Which one of the following complexes will exhibit the least paramagnetic behaviour ? [Atomic number, Cr = 24, Mn = 25, Fe = 26, Co = 27]EasySingle correct
  4. 8 Apr 2024, Shift 2 · Q70Match List - I with List - II. List - I (Complex ion) | List - II (Spin only magnetic moment in B.M.) (A) [Cr(NH3)6]3+[\mathrm{Cr(NH_3)_6}]^{3+} |…MediumMatch the list
  5. 27 Jan 2024, Shift 1 · Q69Consider the following complex ions P=[FeF6]3−\mathrm{P=[FeF_6]^{3-}} Q=[V(H2O)6]2+\mathrm{Q=[V(H_2O)_6]^{2+}} R=[Fe(H2O)6]2+\mathrm{R=[Fe(H_2O)_6]^{2+}} The correct…MediumSingle correct
  6. 31 Jan 2024, Shift 1 · Q86The 'Spin only' Magnetic moment for [Ni(NH3)6]2+[\mathrm{Ni(NH_3)_6}]^{2+} is _________ ×10−1\times10^{-1} BM. (given = Atomic number of Ni : 28)EasyNumerical value
  7. 31 Jan 2024, Shift 2 · Q70Select the option with correct property -MediumSingle correct
  8. 6 Apr 2023, Shift 1 · Q72Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: The spin only magnetic…MediumAssertion–reason

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.