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Chemistry · Coordination Compounds

NEET (UG) 2023 — Question 75

Which complex compound is most stable?

  1. Option A:

    [Co(NH3)3(NO3)3]\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3}\left(\mathrm{NO}_{3}\right)_{3}\right]

  2. Option B:

    [CoCl2( en )2]NO3\left[\mathrm{CoCl}_{2}(\text { en })_{2}\right] \mathrm{NO}_{3}

    Correct
  3. Option C:

    [Co(NH3)6]2(SO4)3\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]_{2}\left(\mathrm{SO}_{4}\right)_{3}

  4. Option D:

    [Co(NH3)4(H2O)Br](NO3)2\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4}\left(\mathrm{H}_{2} \mathrm{O}\right) \mathrm{Br}\right]\left(\mathrm{NO}_{3}\right)_{2}

Answer: B

Step-by-step solution

The stability of a coordination complex is enhanced by chelation. Among the given complexes, only option B contains the bidentate ligand ethylenediamine (en), which forms a chelate ring with the metal ion. The chelate effect (entropic and enthalpic contributions) makes chelated complexes more stable than those with only monodentate ligands. Thus, [CoCl2(en)2]NO3[CoCl_2(en)_2]NO_3 is the most stable complex.

Answer key and solution verified before publishing.

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Exam
NEET (UG) 2023
Paper
2023 paper
Subject
Chemistry
Chapter
Coordination Compounds
Topic
Theories of Bonding in Coordination Compounds

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Which complex compound is most stable? | NEET (UG) 2023 PYQ with Solution · DhiX AI