250+ TOP MCQs on Definitions – Coordination Compounds and Answers

Chemistry Written Test Questions for Schools on “Definitions – Coordination Compounds – 2”.

1. The coordination number is determined by the number of both, sigma and pi bonds formed by the ligand with the central atom/ion.
a) True
b) False
Answer: b
Clarification: The CN is found by only considering the number of sigma bonds between the donor atoms and central atom/ion. Pi bonds between ligand and central atom/ion are not counted for this purpose.

2. The coordination polyhedron geometry shown belongs to which of the following complexes?

a) [Co(NH₃)₆]³⁺
b) [Ni(CO)₄]
c) [CoCl₂(en)₂]²⁺
d) [Fe(C₂O₄)₃]^3-
Answer: b
Clarification: The arrangement shown is tetrahedral and CN=4. [Co(NH₃)₆]³⁺ is octahedral with CN=6. Both [CoCl₂(en)₂]²⁺ and [Fe(C₂O₄)₃]^3- have didentate ligands and hence CN=6.

3. What is the correct way of representing nickel in [Ni(CO)₄]?
a) Ni(0)
b) Ni(I)
c) Ni(II)
d) Ni(III)
Answer: a
Clarification: The oxidation number of a metal is represented as Roman numeral in parenthesis preceded by the name of the entity. Since oxidation number of nickel in the given compound is zero, it is represented as Ni(0).

4. What is the shape of the coordination polyhedron of [PtCl₄]^2-?
a) Linear
b) Square planar
c) Tetrahedral
d) Octahedral
Answer: b
Clarification: The CN of the metal ion is 4 because Cl^– is a unidentate ligand. The only possibility for the shape of its coordination polyhedra is square planar or tetrahedral. From crystal field splitting diagram, it is known that [PtCl₄]^2- is square planar.

5. Complexes in which a metal is attached to only one kind of donor group is called _______
a) Unidentate
b) Chelate
c) Homoleptic
d) Heteroleptic
Answer: c
Clarification: Unidentate and chelate are words associated with ligands, whereas coordination complexes can be either homoleptic or heteroleptic depending upon whether only one kind or different kinds of ligands linked to the metal atom/ion respectively.

6. Which of the following compounds consists of a homoleptic complex?
a) [Co(NH₃)₆]Cl₃
b) [Co(NH₃)₅Cl]Cl₂
c) [Co(NH₃)₄Cl₂]Cl
d) [Co(NH₃)₅(CO₃)]Cl
Answer: a
Clarification: [Co(NH₃)₆]Cl₃ consists of only ammonia ligands in the complex and is hence homoleptic. The rest of the compounds consists of two kinds of ligates, either NH₃ and Cl or NH₃ and CO₃, and hence they are heteroleptic.

7. The oxidation number of the central metal ion in a coordination entity is the charge it would carry if all the _________ are removed along with the electron pairs that are shared with it.
a) lewis acids
b) anions
c) ligands
d) didentate ligands
Answer: c
Clarification: The oxidation number or primary valence of a central atom is its charge if all the ligands and its donor atoms are not present in the coordination entity.

8. The oxidation number of the central metal in a coordination entity is always a positive quantity.
a) True
b) False
Answer: b
Clarification: The oxidation number might not always be positive. It can also be 0 or a negative value. For example, the oxidation number of cobalt in K[Co(CO)₄] is -1.

9. What is the denticity of the ligand shown in the figure?

a) 2
b) 4
c) 6
d) 8
Answer: c
Clarification: The ion shown in the figure is ethylenediaminetetraacetate which is a hexadentate ligand and can bind through its two N atoms or four O atoms. Hence, its denticity is 6.

10. When a polydentate ligand uses all its donor atoms simultaneously to bond to a single metal ion, it is said to be a _______ ligand.
a) unidentate
b) didentate
c) chelate
d) ambidentate
Answer: c
Clarification: Unidentate ligands use only one donor atom at a time. Didentate are polydentate ligands that have two donor atoms. An ambidentate ligand can bind through different donor atoms.

Chemistry Written Test Questions for Schools,