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Friday, 9 October

JEE Main 2021 · ChemistryMultiple choiceSingle correctMediumRecall

JEE Main 3 August 2021, Shift 2, Chemistry Q42

Question 42 of 90 in this shift, Chemistry question 12 of 30, Section A.

In the detection of nitrogen in an organic compound by Lassaigne's test, the iron compounds formed are
  1. (1)[Fe(CN)6]3−\mathrm{[Fe(CN)_6]^{3-}}, Fe[Fe(CN)6]⋅xH2O\mathrm{Fe[Fe(CN)_6]\cdot xH_2O}
  2. (2)[Fe(CN)6]4−\mathrm{[Fe(CN)_6]^{4-}}, Fe2[Fe(CN)6]⋅xH2O\mathrm{Fe_2[Fe(CN)_6]\cdot xH_2O}
  3. (3)[Fe(CN)6]4−\mathrm{[Fe(CN)_6]^{4-}}, Fe4[Fe(CN)6]3⋅xH2O\mathrm{Fe_4[Fe(CN)_6]_3\cdot xH_2O}Official answer
  4. (4)[Fe(CN)6]3−\mathrm{[Fe(CN)_6]^{3-}}, Fe3[Fe(CN)6]2⋅xH2O\mathrm{Fe_3[Fe(CN)_6]_2\cdot xH_2O}

Official answer

Option 3

NTA final key.

Chapter
Organic Chemistry: Some Basic Principles and Techniques
Topic
Anion Analysis
Idea tested
Cyanide Prussian Blue Test

Same idea in other shifts

Asked 2× in all
  1. 8 Apr 2024, Shift 1 · Q73Match List I with List II LIST I (Compound): A. Fe4[Fe(CN)6]3⋅xH2O\mathrm{Fe_4[Fe(CN)_6]_3\cdot xH_2O}; B. [Fe(CN)5NOS]4−[\mathrm{Fe(CN)_5NOS}]^{4-}; C.…MediumMatch the list

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 42 of the 174 JEE Main shifts held from 2017 to 2026.