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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumCalculation

JEE Main 31 August 2021, Shift 2, Chemistry Q39

Question 39 of 90 in this shift, Chemistry question 9 of 30, Section A.

Spin only magnetic moment in BM of [Fe(CO)4(C2O4)]+[\mathrm{Fe(CO)_4(C_2O_4)}]^+ is :
  1. (1)1
  2. (2)1.73Official answer
  3. (3)5.92
  4. (4)0

Official answer

Option 2

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.