CPC Inorganic Chemistry & Coordination Compounds

Question 1

What is the coordination number of the central metal ion in [Co(NH3)6]3+?

Accepted Answer

6

Answer

The coordination number equals the number of ligands directly bonded to the central metal; in [Co(NH3)6]3+, six NH3 molecules coordinate to cobalt.

Question 2

Which of the following best describes a chelating ligand?

Accepted Answer

A ligand that binds to the metal at two or more donor atoms, forming a ring

Answer

Chelating (polydentate) ligands coordinate through two or more donor atoms simultaneously, forming a ring structure with the metal center.

Question 3

What is the ground-state electron configuration of Fe2+?

Accepted Answer

[Ar] 3d6

Answer

Neutral Fe is [Ar] 3d6 4s2; losing two electrons removes the 4s electrons first, yielding [Ar] 3d6 for Fe2+.

Question 4

In an octahedral crystal field, which d-orbitals constitute the eg set?

Accepted Answer

dx²−y² and dz²

Answer

The eg set (dx²−y² and dz²) points directly toward the six ligands along the axes and is destabilized more than the t2g set.

Question 5

What type of isomerism is exhibited by [Co(NH3)4Cl2]NO2 and [Co(NH3)4ClNO2]Cl?

Accepted Answer

Ionization isomerism

Answer

Ionization isomers produce different ions in solution; the first complex releases NO2− while the second releases Cl− as the counter ion.

(CPC) Certified Professional Chemist Practice Test