Verified Solution • 2025–26 Session moderate

QJEEAdv20Ch3236: JEE Advanced 2020 Chemistry - Class 12 JEEAdv20Ch3236 Solution: Choose the correct statement(s) among the following :

Choose the correct statement(s) among the following :

Multiple Choice Options

  • A [FeCl4] −- has tetrahedral geometry.
  • B [Co(en)(NH3)2Cl2]+ has 2 geometrical isomers.
  • C [FeCl4] −- has higher spin-only magnetic moment than [Co(en)(NH3)2Cl2]+.
  • D The cobalt ion in [Co(en)(NH3)2Cl2]+ has sp3d2 hybridisation.

Step-by-Step Verified Solution

(a) In [FeCl4]-, oxidation number of Fe atom = +3

Electronic configuration of Fe in ground state = 3d64s2

Electronic configuration of

Fe3+ = 3d54s04p0

JEE Advanced 2020 Paper 1 Offline Chemistry - Coordination Compounds Question 36 English Explanation 1

Thus, [FeCl4]- has tetrahedral geometry.

(b) [Co(en)(NH3)2Cl2]+ have three geometrical isomers. Thus, statement (b) is incorrect.

JEE Advanced 2020 Paper 1 Offline Chemistry - Coordination Compounds Question 36 English Explanation 2

(c) Fe3+ in [FeCl4]- is sp3-hybridised with 5 unpaired electrons. (higher spin-only magnetic moment

= n(n+2)\sqrt {n(n + 2)} = 5.92 BM). While Co3+ in [Co(en)(NH3)2Cl2]+ is d2sp3-hybridised with zero unpaired electrons (low spin-only magnetic moment = n(n+2)\sqrt {n(n + 2)} = 0 BM).

Thus, the statement (c) is correct.

(d) Co3+[Co(en)(NH3)2Cl2]+

JEE Advanced 2020 Paper 1 Offline Chemistry - Coordination Compounds Question 36 English Explanation 3

Co3+ in [Co(en)(NH3)2Cl2]+ is d2sp3-hybridised and has octahedral geometry with 0 unpaired electron. Thus, statement (d) is incorrect.

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