Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Coordination Compounds question

2025 · 29 Jan · Shift 2 · Q8
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Chemistry
  4. /Coordination Compounds
  5. /2025 · 29 Jan · Shift 2 · Q8

Coordination Compounds question

2025 · 29 Jan · Shift 2 · Q8

JEE MainChemistryCoordination CompoundsMCQ+4 / −1
Identify the homoleptic complexes with odd number of ddd electrons in the central metal : (A) [FeO4]2−\left[\mathrm{FeO}_4\right]^{2-}[FeO4​]2−(B) [Fe(CN)6]3−\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}[Fe(CN)6​]3−(C) [Fe(CN)5NO]2−\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NO}\right]^{2-}[Fe(CN)5​NO]2−(D) [CoCl4]2−\left[\mathrm{CoCl}_4\right]^{2-}[CoCl4​]2−(E) [Co(H2O)3 F3]\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_3 \mathrm{~F}_3\right][Co(H2​O)3​ F3​] Choose the correct answer from the options given below :
  1. A
    (C) and (E) only
  2. B
    (A), (B) and (D) only
  3. C
    (B) and (D) only
  4. D
    (A), (C) and (E) only
View written solutionFree

Correct answer: C

  1. First identify which complexes are homoleptic

A homoleptic complex has only one kind of ligand attached to the metal.

  • (A) [FeO4]2−[\mathrm{FeO}_4]^{2-}[FeO4​]2− : only O2−\mathrm{O}^{2-}O2− ligands ⇒\Rightarrow⇒ homoleptic
  • (B) [Fe(CN)6]3−[\mathrm{Fe}(\mathrm{CN})_6]^{3-}[Fe(CN)6​]3− : only CN−\mathrm{CN}^-CN− ligands ⇒\Rightarrow⇒ homoleptic
  • (C) [Fe(CN)5NO]2−[\mathrm{Fe}(\mathrm{CN})_5\mathrm{NO}]^{2-}[Fe(CN)5​NO]2− : CN−\mathrm{CN}^-CN− and NO\mathrm{NO}NO both present ⇒\Rightarrow⇒ heteroleptic
  • (D) [CoCl4]2−[\mathrm{CoCl}_4]^{2-}[CoCl4​]2− : only Cl−\mathrm{Cl}^-Cl− ligands ⇒\Rightarrow⇒ homoleptic
  • (E) [Co(H2O)3F3][\mathrm{Co}(\mathrm{H}_2\mathrm{O})_3\mathrm{F}_3][Co(H2​O)3​F3​] : H2O\mathrm{H_2O}H2​O and F−\mathrm{F}^-F− both present ⇒\Rightarrow⇒ heteroleptic

So only (A), (B), (D) are homoleptic. Now check whether the central metal has an odd number of ddd electrons.


  1. Option (A): [FeO4]2−[\mathrm{FeO}_4]^{2-}[FeO4​]2−

Let oxidation state of Fe be xxx.

x+4(−2)=−2x + 4(-2) = -2x+4(−2)=−2 x−8=−2x - 8 = -2x−8=−2 x=+6x = +6x=+6

Fe: Z=26Z=26Z=26, ground state [Ar]3d64s2[\mathrm{Ar}]3d^64s^2[Ar]3d64s2

For Fe6+\mathrm{Fe}^{6+}Fe6+, remove 222 electrons from 4s4s4s and 444 from 3d3d3d:

Fe6+:3d2\mathrm{Fe}^{6+} : 3d^2Fe6+:3d2

Number of ddd electrons =2=2=2 (even), so not required.


  1. Option (B): [Fe(CN)6]3−[\mathrm{Fe}(\mathrm{CN})_6]^{3-}[Fe(CN)6​]3−

Let oxidation state of Fe be xxx.

x+6(−1)=−3x + 6(-1) = -3x+6(−1)=−3 x−6=−3x - 6 = -3x−6=−3 x=+3x = +3x=+3

So,

Fe3+:3d5\mathrm{Fe}^{3+} : 3d^5Fe3+:3d5

Number of ddd electrons =5=5=5 (odd), so required.


  1. Option (D): [CoCl4]2−[\mathrm{CoCl}_4]^{2-}[CoCl4​]2−

Let oxidation state of Co be xxx.

x+4(−1)=−2x + 4(-1) = -2x+4(−1)=−2 x−4=−2x - 4 = -2x−4=−2 x=+2x = +2x=+2

Co: Z=27Z=27Z=27, ground state [Ar]3d74s2[\mathrm{Ar}]3d^74s^2[Ar]3d74s2

For Co2+\mathrm{Co}^{2+}Co2+:

Co2+:3d7\mathrm{Co}^{2+} : 3d^7Co2+:3d7

Number of ddd electrons =7=7=7 (odd), so required.


  1. Now collect the correct homoleptic complexes with odd number of ddd electrons

These are:

  • (B) [Fe(CN)6]3−[\mathrm{Fe}(\mathrm{CN})_6]^{3-}[Fe(CN)6​]3−
  • (D) [CoCl4]2−[\mathrm{CoCl}_4]^{2-}[CoCl4​]2−

Thus the correct choice is:

(B) and (D) only\boxed{\text{(B) and (D) only}}(B) and (D) only​

which corresponds to Option C.


  1. Comparison with stored correct answer

Stored correct answer = C

Derived answer = C

So they agree.

PreviousNext

More from Coordination Compounds

  • Given below are two statements : Statement (I) : A solution of [Ni(H2​O)6​]2+ is green in colour. Statement (II) : A solution of [Ni(CN)4​]2− is…2024 · MCQ
  • Which of the following complex is homoleptic?2024 · MCQ
  • Which of the following compounds show colour due to d-d transition?2024 · MCQ
  • [Co(NH3​)6​]3+ and [CoF6​]3− are respectively known as :2024 · MCQ
  • Given below are two statements : Statement (I) : Dimethyl glyoxime forms a six-membered covalent chelate when treated with NiCl2​ solution in presence of NH4​OH. Statement (II) : Prussian blue precipitate…2024 · MCQ
  • Number of complexes from the following with even number of unpaired "d" electrons is ​ [V(H2​O)6​]3+,[Cr(H2​O)6​]2+,[Fe(H2​O)6​]3+,[Ni(H2​O)6​]3+,[Cu(H2​O)6​]2+…2024 · MCQ
  • The correct sequence of ligands in the order of decreasing field strength is :2024 · MCQ
  • A first row transition metal in its +2 oxidation state has a spin-only magnetic moment value of 3.86 BM. The atomic number of the metal is2024 · MCQ