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Saturday, 31 October

JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumMulti-step

JEE Main 4 August 2021, Shift 1, Chemistry Q57

Question 57 of 90 in this shift, Chemistry question 27 of 30, Section B.

Among the following species, the number of species with oxidation state of Fe in +3 is ________. A. [(H2O)4(CN)Fe(μ-OH)2Fe(CN)(H2O)4]2+\mathrm{[(H_2O)_4(CN)Fe(\mu\text{-}OH)_2Fe(CN)(H_2O)_4]^{2+}} [drawn structure, see figure_note] B. [Fe3O(CH3COO)6(H2O)3]+\mathrm{[Fe_3O(CH_3COO)_6(H_2O)_3]^{+}} C. [Fe(CN)(CO)(NH3)3(H2O)]+\mathrm{[Fe(CN)(CO)(NH_3)_3(H_2O)]^{+}}

The figure, in words

Species A is drawn inside square brackets with charge 2+: '(H2O)4(CN)Fe' on the left and 'Fe(CN)(H2O)4' on the right joined by a four-membered diamond ring through two bridging O atoms, one above (with H on top of it) and one below (with H below it), each O bonded to both Fe atoms. B and C are printed as formulas. In B the subscripts printed are Fe3O(CH3COO)6(H2O)3 with charge +; in C Fe(CN)(CO)(NH3)3(H2O) with charge +.

Official answer

2

NTA final key.

Chapter
Coordination Compounds
Topic
Coordination Nomenclature
Idea tested
Oxidation State Calculation

Same idea in other shifts

Asked 7× in all
  1. 8 Apr 2024, Shift 1 · Q70An octahedral complex with the formula CoCl3⋅nNH3\mathrm{CoCl_3\cdot nNH_3} upon reaction with excess of AgNO3\mathrm{AgNO_3} solution gives 2 moles…MediumSingle correct
  2. 29 Jul 2022, Shift 2 · Q86Sum of oxidation state (magnitude) and coordination number of cobalt in Na[Co(bpy)Cl4]\mathrm{Na[Co(bpy)Cl_4]} is ____. (Given: bpy = [figure:…EasyNumerical valueHas a figure
  3. 30 Jul 2022, Shift 2 · Q50In the ring test of NO3−\mathrm{NO_3^-} ion what is the oxidation number of iron in the complex (brown ring)…MediumSingle correct
  4. 3 Aug 2021, Shift 2 · Q40The oxidation states of Fe in [Fe(NCS)(NH3)5]SO4\mathrm{[Fe(NCS)(NH_3)_5]SO_4}, Na3[Fe(S2O3)3]\mathrm{Na_3[Fe(S_2O_3)_3]} and [Fe(CO)5]\mathrm{[Fe(CO)_5]} respectively areEasySingle correct
  5. 4 Aug 2021, Shift 2 · Q38The oxidation states of Mn in Mn2(CO)10\mathrm{Mn_2(CO)_{10}}, [Mn(CO)5Br]\left[\mathrm{Mn(CO)_5Br}\right] and K[Mn(CN)6]\mathrm{K}\left[\mathrm{Mn(CN)_6}\right]…EasySingle correct
  6. 2 Sep 2020, Shift 1 · Q49The oxidation states of iron atoms in compounds (A), (B) and (C), respectively, are xx, yy and zz. The sum of xx, yy and zz is…MediumNumerical value

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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.