Werner's theory, ligands coordination number denticity and chelation - Question Bank

1. Which of the following is a common example of a chelating agent used to remove heavy metal ions from the body?
A) Sodium chloride
B) Aspirin
C) BAL (British Anti-Lewisite)
D) Glucose
2. The number of ionizable chloride ions in the complex [Co(NH3)5Cl]Cl2 is:
A) 1
B) 2
C) 3
D) 5
3. Werner's theory successfully explained the properties of coordination compounds by proposing the existence of:
A) Ionic bonds only
B) Covalent bonds only
C) Primary and secondary valencies
D) Metallic bonds
4. In the complex [Cr(en)3]^3+, the denticity of ethylenediamine (en) and the coordination number of Chromium (Cr) are respectively:
A) 1, 3
B) 2, 3
C) 3, 2
D) 2, 6
5. The chelate effect is a manifestation of:
A) Thermodynamic stability
B) Kinetic stability
C) Entropy effect
D) Enthalpy effect
6. The complex [Co(NH3)5Cl]Cl2 shows that the five ammonia molecules and one chloride ion are attached to Co by secondary valencies. What is the coordination number of Co in this complex?
A) 5
B) 6
C) 7
D) 8
7. A ligand that can coordinate through one donor atom is termed:
A) Bidentate
B) Tridentate
C) Monodentate
D) Polydentate
8. The secondary valency in Werner's theory is generally fixed for a given metal ion and is equal to its:
A) Atomic number
B) Mass number
C) Coordination number
D) Oxidation state
9. Which of the following coordination compounds exhibits the chelate effect?
A) [Ni(CN)4]^2-
B) [Co(NH3)6]^3+
C) [Cu(en)2]^2+
D) [Fe(H2O)6]^3+
10. The denticity of the diamine ligand, NH2-CH2-CH2-NH2, is:
A) 1
B) 2
C) 3
D) 4
11. In Werner's original work, the complex [Co(NH3)6]Cl3 was explained as having Co linked to six ammonia molecules by secondary valencies and the three chloride ions satisfied the primary valencies. What is the oxidation state of Co in this complex?
A) 0
B) +1
C) +2
D) +3
12. The coordination number of a central metal atom represents the total number of:
A) Ligands attached
B) Donor atoms attached
C) Coordinate bonds formed
D) All of the above
13. Which of the following is a bidentate ligand?
A) Ammonia (NH3)
B) Carbon monoxide (CO)
C) Dipyridyl (bpy)
D) Sulfide ion (S^2-)
14. The primary valency of a metal ion in a coordination compound is typically satisfied by:
A) Ligands
B) Anions
C) Cations
D) Neutral molecules
15. A ligand capable of coordinating through three donor atoms is called:
A) Monodentate
B) Bidentate
C) Tridentate
D) Tetradentate
16. What is the coordination number of Platinum (Pt) in the complex [PtCl4]^2-?
A) 1
B) 2
C) 4
D) 6
17. Which of the following statements about chelation is FALSE?
A) Chelation involves polydentate ligands.
B) Chelation leads to increased stability of complexes.
C) Chelation requires only one donor atom from the ligand.
D) Chelation forms a ring structure.
18. The term 'ligand' originates from the Latin word 'ligare' meaning:
A) To break
B) To bind
C) To separate
D) To dissolve
19. In the complex [Cu(NH3)4]^2+, the coordination number of Copper (Cu) is:
A) 2
B) 4
C) 8
D) 12
20. Which of the following is a hexadentate ligand commonly used in analytical chemistry?
A) Ethylenediamine
B) Bipyridine
C) EDTA
D) Glycine
21. The denticity of the thiocyanate ion (SCN-) can be:
A) 1 only
B) 2 only
C) 1 or 2
D) 3
22. Which of the following is NOT a characteristic of Werner's theory?
A) Primary valency is ionizable.
B) Secondary valency is non-directional.
C) Ligands are attached by secondary valencies.
D) Coordination number is usually fixed for a given metal ion.
23. In [Ni(CO)4], the coordination number of Nickel (Ni) is:
A) 1
B) 2
C) 3
D) 4
24. The phenomenon where a polydentate ligand forms a stable ring structure with a metal ion is called:
A) Complexation
B) Chelation
C) Coordination
D) Polymerization
25. What is the denticity of the acetylacetonate (acac) ligand?
A) 1
B) 2
C) 3
D) 4
26. The complex ion [Fe(CN)6]^3- has a coordination number of:
A) 1
B) 3
C) 6
D) 12
27. Which of the following ligands can form a chelate ring with a metal ion?
A) Cl-
B) H2O
C) en (ethylenediamine)
D) CO
28. In Werner's theory, which valency satisfies the coordination number of the metal ion?
A) Primary valency
B) Secondary valency
C) Both
D) Neither
29. What is the denticity of the cyanide ion (CN-)?
A) 1
B) 2
C) 3
D) 4
30. The number of coordinate bonds formed by a ligand with the central metal atom is called its:
A) Coordination number
B) Denticity
C) Chelation index
D) Valency
31. Which of the following is a polydentate ligand?
A) H2O
B) NH3
C) CO
D) EDTA
32. In [Co(en)2Cl2]+, how many donor atoms are contributed by the ethylenediamine (en) ligands?
A) 2
B) 4
C) 6
D) 8
33. In the complex [Co(en)2Cl2]+, what is the coordination number of Co?
A) 2
B) 3
C) 4
D) 6
34. Which of the following complexes is expected to be more stable, [Fe(CN)6]^4- or [Fe(en)3]^2+?
A) [Fe(CN)6]^4-
B) [Fe(en)3]^2+
C) They have equal stability
D) Stability cannot be determined
35. The stability of coordination complexes formed by chelating ligands is known as the:
A) Ligand effect
B) Chelate effect
C) Coordination effect
D) Werner effect
36. Which type of ligands are more effective in stabilizing coordination complexes due to the formation of a ring structure?
A) Monodentate ligands
B) Bidentate ligands
C) Chelating ligands
D) Anionic ligands
37. The process of formation of a chelate ring by a polydentate ligand with a metal ion is known as:
A) Coordination
B) Chelation
C) Ionization
D) Dissociation
38. What is the denticity of the oxalate ion (C2O4^2-)?
A) 1
B) 2
C) 3
D) 4
39. The ED TA ligand is an example of which type of ligand based on denticity?
A) Monodentate
B) Bidentate
C) Hexadentate
D) Octadentate
40. What is the denticity of the ethylenediamine (en) ligand?
A) 1
B) 2
C) 3
D) 4
41. A ligand that can bind to the central metal atom through two donor atoms is called:
A) Monodentate
B) Bidentate
C) Tridentate
D) Polydentate
42. Which of the following is a monodentate ligand?
A) Ethylenediamine (en)
B) Oxalate (ox)
C) Chloride ion (Cl-)
D) Acetylacetonate (acac)
43. What is the coordination number of the central metal ion in the complex [PtCl2(en)2]?
A) 2
B) 3
C) 4
D) 6
44. For a complex like [Co(NH3)6]3+, what is the coordination number of Cobalt (Co)?
A) 1
B) 3
C) 6
D) 9
45. The number of donor atoms attached to the central metal atom in a coordination complex is called the:
A) Denticity
B) Coordination number
C) Chelation number
D) Ligand number
46. What is the term used for a molecule or ion that binds to a central metal atom to form a coordination complex?
A) Counter ion
B) Ligand
C) Chelating agent
D) Oxidizing agent
47. Which type of valency is responsible for the formation of the complex ion in a coordination compound?
A) Primary valency
B) Secondary valency
C) Both primary and secondary
D) Neither primary nor secondary
48. Secondary valency in coordination compounds, according to Werner, is directed towards:
A) The counter ions
B) The solvent molecules
C) The ligands
D) The surrounding atoms in the crystal lattice
49. In Werner's theory, primary valency is generally considered equivalent to:
A) Coordination number
B) Oxidation state
C) Ligand number
D) Chelate effect
50. According to Werner's theory, what are the two types of valencies exhibited by the central metal atom in a coordination compound?
A) Primary and secondary
B) Ionic and covalent
C) Sigma and pi
D) Oxidation and coordination
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