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Chemistry · Practical Inorganic chemistry (Qualitative Analysis)

JEE Main 2025 — 24 January, Evening Shift — Question 30

Find the compound 'A' from the following reaction sequences.

A→ aqua-regia B→(2)AcOH(1)KNO2/NH4OH\mathrm{A} \xrightarrow{\text { aqua-regia }} \mathrm{B} \xrightarrow[(2) \mathrm{AcOH}]{(1) \mathrm{KNO}_{2} / \mathrm{NH}_{4} \mathrm{OH}} yellow ppt

  1. Option A:

    ZnS

  2. Option B:

    CoS

    Correct
  3. Option C:

    MnS

  4. Option D:

    NiS

Answer: B

Step-by-step solution

3 CoS(s)+2 HNOX3(aq)+12 HCl(aq)→3 CoClX2(aq)+3 S(s)+2 NO(g)+8 HX2O(l)\ce{3CoS(s) + 2HNO3(aq) + 12HCl(aq) -> 3CoCl2(aq) + 3S(s) + 2NO(g) + 8H2O(l)}

CoCl2→2.AcOH1.KNO2/NH4OH \mathrm{CoCl}_{2} \xrightarrow[2 . \mathrm{AcOH}]{1 . \mathrm{KNO_2} / \mathrm{NH}_{4} \mathrm{OH}} K3[Co(NO2)6]↓\mathrm{K}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right] \downarrow yellow

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
24 January, Evening Shift
Subject
Chemistry
Chapter
Practical Inorganic chemistry (Qualitative Analysis)
Topic
Identification of Cations (Groups 1 to 3)