Chemistry

Coordination Chemistry

325 Questions

Coordination chemistry focuses on coordination compounds, their structures, and their magnetic properties. The questions cover primary and secondary valencies, ligand types, and geometries of complexes. This topic is heavily tested in chemistry competitive exams and requires a good grasp of molecular structures.

primary and secondary valencycomplex geometriesligand field theorymagnetic properties of complexesisomerism in complexes

Coordination Chemistry Questions

Multiple choice

Which of the following complexes are diamagnetic in nature? P. [CoF6]3- Q. [Fe(CN)6]4- R. Zn(H2O)6]2+ S. [Cr(H2O)6]3+

  1. Only P and Q

  2. Only P and S

  3. Only Q and R

  4. Only Q and S

  5. Only R and S
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is incorrect. [Fe(CN)6]4- is an inner orbital complex with octahedral geometry (d2sp3 hybridisation); No unpaired electrons; diamagnetic

Zn(H2O)6]2+ is an outer orbital complex with square planar geometry (sp3d2 hybridisation); No unpaired electrons; diamagnetic

Multiple choice

Which of the following sets represents diamagnetic metal ions only?

  1. Mn3+, Fe2+, Ni2+, Zn2+

  2. Ti4+, Ni2+, Cu+, Zn2+

  3. Mn3+, Fe3+, Ni2+, Cu2+

  4. Sc3+, Fe3+, Ni2+, Cu2+

  5. Sc3+, Ti4+, Cu+, Zn2+
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Sc3+: 3d0, No unpaired electrons; diamagnetic. Ti4+: 3d0, No unpaired electrons; diamagnetic. Cu+: 3d10, 1 unpaired electron; diamagnetic. Zn2+: 3d10, No unpaired electrons; diamagnetic.

Multiple choice

Which one of the following transition metal ions is expected to form coloured complexes?

  1. Mn2+
  2. Fe3+
  3. Zn2+

Select the correct answer using codes given below:

  1. 1 and 2

  2. 1 and 3

  3. 2 and 3

  4. 1, 2 and 3

  5. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mn: 3d54s2 Mn2+: 3d5 In Mn2+ d orbitals are not completely filled, so it is expected to form coloured complexes.

Fe: 3d64s2 Fe3+: 3d5 In Fe3+ d orbitals are not completely filled, so it is expected to form coloured complexes.

Multiple choice

Arrange the following central metal ions in order of increasing nephelauxetic effect.

a. Co(III) b. Ir(III) c. Fe(III)

  1. a < b < c

  2. a < c < b

  3. b < a < c

  4. c < b < a

  5. c < a < b
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The nephelauxetic effect not only depends upon the ligand type, but also upon the central metal ion. These too can be arranged in order of increasing nephelauxetic effect as follows: Mn(II) < Ni(II) ≈ Co(II) < Mo(II) < Re(IV) < Fe(III) < Ir(III) < Co(III) < Mn(IV).

Multiple choice

Which of the following is a pair of paramagnetic complexes?

  1. [W(CO)6] and [Cr(NH3)6]3+

  2. [Co(NH3)6]3+ and [W(CO)6]

  3. [Fe(CN)6]3- and [Co(NH3)6]3+

  4. [Co(NH3)6]3+ and [Cr(NH3)6]3+

  5. [Cr(NH3)6]3+ and [Fe(CN)6]3-
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

[Cr(NH3)6]3+: t2g3 eg0; 3 unpaired electrons; paramagnetic [Fe(CN)6]3-: t2g5 eg0; one unpaired electron; paramagnetic

Multiple choice

Geometrical isomerism is exhibited by

  1. [Zn(NH3)2Cl2]

  2. [Co(NH3)6]3+

  3. [Pt(NH3)2Cl2]

  4. [Ni(CN)4]2-

  5. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

[Pt(NH3)2Cl2] is a heteroleptic square planar complex of Ma2b2 type. In a square planar complex of formula [Ma2b2], the two similar ligands may be arranged adjacent to each other in a cis isomer or opposite to each other in a trans isomer.

Multiple choice

Which of the following statements is incorrect?

  1. [Mn(CN)6]3-, [Fe(CN)6]3- and [Co(C2O4)3]3- are diamagnetic inner orbital complexes that involve d2sp3 hybridisation.

  2. The ligand field strength increases in the order SCN- < C2O42- < NCS- < en < CO.

  3. [Mn2(CO)10] has one Mn-Mn bond and [Co2(CO)8] has one Co-Co bond.

  4. [MnCl6]3-, [FeF6]3- and [CoF6]3- are paramagnetic outer orbital complexes that involve sp3d2 hybridisation.

  5. M-C bond length in [Fe(CN)6]3- is lower than that in [Mn(CN)6]3-.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Correct Answer: [Mn(CN)6]3-, [Fe(CN)6]3- and [Co(C2O4)3]3- are diamagnetic inner orbital complexes that involve d2sp3 hybridisation.

Multiple choice

Primary valency of iron in K4 [Fe (CN)6] is

  1. 2

  2. 3

  3. 4

  4. 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In K4[Fe(CN)6], the primary valency corresponds to the oxidation state of the central metal ion. Since the total charge of the complex is 0 and CN is -1, Fe + 6(-1) = -4, so Fe = +2.