Coordination Chemistry MCQs
1. What is a metal complex?
- a) A metal bonded to another metal
- b) A central metal atom bonded to a group of molecules or ions
- c) A metal bonded to a non-metal
- d) A metal bonded to a gas
2. What is a complex ion?
- a) A neutral complex
- b) A charged complex
- c) A complex with no ligands
- d) A complex with only water ligands
3. What are ligands?
- a) Molecules or ions that bond to a central metal atom
- b) Only anions that bond to metals
- c) Only polar molecules that bond to metals
- d) Molecules that do not bond to metals
4. Which of the following is NOT a ligand?
- a) NH₃
- b) Cl⁻
- c) H₂O
- d) Na⁺
5. What is the coordination number of Co(III) in [Co(NH₃)₆]Cl₃?
- a) 3
- b) 4
- c) 5
- d) 6
6. According to Werner’s theory, what is the primary valence of a metal ion?
- a) The number of ligands bonded to the metal
- b) The oxidation number of the metal
- c) The charge on the complex ion
- d) The number of atoms in the coordination sphere
7. What is the secondary valence in Werner’s theory?
- a) The oxidation number of the metal
- b) The number of atoms directly bonded to the metal (coordination number)
- c) The charge on the complex ion
- d) The number of free ions in the solution
8. Which of the following complexes is green in color?
- a) [Co(NH₃)₆]Cl₃
- b) [Co(NH₃)₅Cl]Cl₂
- c) trans-[Co(NH₃)₄Cl₂]Cl
- d) cis-[Co(NH₃)₄Cl₂]Cl
9. What is the modern formulation of CoCl₃·6NH₃?
- a) [Co(NH₃)₆]Cl₃
- b) [Co(NH₃)₅Cl]Cl₂
- c) [Co(NH₃)₄Cl₂]Cl
- d) [Co(NH₃)₃Cl₃]
10. What is the coordination sphere in a complex?
- a) The central metal and the ligands directly bonded to it
- b) The free ions in the solution
- c) The ligands outside the coordination sphere
- d) The solvent molecules
11. Which of the following is a bidentate ligand?
- a) NH₃
- b) H₂O
- c) en (ethylenediamine)
- d) Cl⁻
12. What is the name of the ligand EDTA?
- a) Ethylenediaminetetraacetate
- b) Ethylenediaminetriacetate
- c) Ethylenediaminediacetate
- d) Ethylenediamine
13. What is the oxidation number of Cu in [Cu(NH₃)₄]²⁺?
- a) +1
- b) +2
- c) +3
- d) +4
14. What is the charge on the complex ion [Cr(H₂O)₄Cl₂]?
- a) +1
- b) +2
- c) +3
- d) 0
15. Which of the following is a polydentate ligand?
- a) NH₃
- b) H₂O
- c) EDTA
- d) Cl⁻
16. What is the coordination number of Cr(III) in [Cr(H₂O)₆]³⁺?
- a) 4
- b) 5
- c) 6
- d) 7
17. Which of the following is a square planar complex?
- a) [Co(NH₃)₆]³⁺
- b) [Pt(NH₃)₂Cl₂]
- c) [Fe(CN)₆]⁴⁻
- d) [Ni(CO)₄]
18. What is the name of the complex [Co(NH₃)₅Cl]Cl₂?
- a) Pentaamminechlorocobalt(III) chloride
- b) Pentachlorocobalt(III) ammine
- c) Pentaamminecobalt(III) chloride
- d) Chloropentaamminecobalt(III) chloride
19. Which of the following is an example of a linkage isomer?
- a) [Co(NH₃)₅NO₂]²⁺
- b) [Co(NH₃)₅Cl]²⁺
- c) [Co(NH₃)₆]³⁺
- d) [Co(en)₃]³⁺
20. What is the color of [Ti(H₂O)₆]³⁺?
- a) Green
- b) Purple
- c) Yellow
- d) Blue
21. Which of the following ligands is the strongest field ligand?
- a) Cl⁻
- b) H₂O
- c) NH₃
- d) CN⁻
22. What is the spectrochemical series?
- a) A series of metals arranged by their reactivity
- b) A series of ligands arranged by their strength of interaction with metal ions
- c) A series of complexes arranged by their color
- d) A series of coordination numbers
23. What is the splitting of d-orbitals in an octahedral field called?
- a) Crystal field splitting
- b) Ligand field splitting
- c) Molecular orbital splitting
- d) Hybridization
24. Which of the following is a high-spin complex?
- a) [Co(CN)₆]³⁻
- b) [CoF₆]³⁻
- c) [Co(NH₃)₆]³⁺
- d) [Co(en)₃]³⁺
25. What is the geometry of [Ni(CO)₄]?
- a) Tetrahedral
- b) Square planar
- c) Octahedral
- d) Linear
26. Which of the following is an example of a geometric isomer?
- a) [Co(NH₃)₅Cl]²⁺
- b) [Pt(NH₃)₂Cl₂]
- c) [Co(en)₃]³⁺
- d) [Fe(CN)₆]⁴⁻
27. What is the name of the complex [Cr(H₂O)₄Cl₂]Cl?
- a) Tetrachlorodiaquachromium(III) chloride
- b) Dichlorotetraaquachromium(III) chloride
- c) Tetraaquadichlorochromium(III) chloride
- d) Dichlorotetraaquachromium(II) chloride
28. Which of the following is an example of an optical isomer?
- a) [Co(NH₃)₅Cl]²⁺
- b) [Co(en)₃]³⁺
- c) [Pt(NH₃)₂Cl₂]
- d) [Fe(CN)₆]⁴⁻
29. What is the color of [Cr(H₂O)₆]³⁺?
- a) Green
- b) Violet
- c) Yellow
- d) Blue
30. Which of the following is a low-spin complex?
- a) [CoF₆]³⁻
- b) [Co(CN)₆]³⁻
- c) [Co(H₂O)₆]³⁺
- d) [Co(NH₃)₆]³⁺
31. What is the name of the complex [Co(NH₃)₄Cl₂]Cl?
- a) Tetraamminedichlorocobalt(III) chloride
- b) Dichlorotetraamminecobalt(III) chloride
- c) Tetraamminecobalt(III) dichloride
- d) Dichlorotetraamminecobalt(II) chloride
32. Which of the following is a chelating agent?
- a) NH₃
- b) H₂O
- c) EDTA
- d) Cl⁻
33. What is the oxidation number of Cr in [Cr(H₂O)₄Cl₂]Cl?
- a) +1
- b) +2
- c) +3
- d) +4
34. Which of the following is a tetradentate ligand?
- a) NH₃
- b) en (ethylenediamine)
- c) EDTA
- d) Cl⁻
35. What is the color of [Cr(CN)₆]³⁻?
- a) Green
- b) Violet
- c) Yellow
- d) Blue
36. Which of the following is a high-spin complex?
- a) [Co(CN)₆]³⁻
- b) [CoF₆]³⁻
- c) [Co(NH₃)₆]³⁺
- d) [Co(en)₃]³⁺
37. What is the geometry of [Pt(NH₃)₂Cl₂]?
- a) Tetrahedral
- b) Square planar
- c) Octahedral
- d) Linear
38. Which of the following is an example of a coordination-sphere isomer?
- a) [Co(NH₃)₅Cl]Cl₂
- b) [Co(NH₃)₅NO₂]Cl₂
- c) [Co(NH₃)₆]Cl₃
- d) [Co(en)₃]Cl₃
39. What is the name of the complex [Co(NH₃)₅NO₂]Cl₂?
- a) Pentaamminechlorocobalt(III) chloride
- b) Pentaamminecobalt(III) nitrite chloride
- c) Pentaamminecobalt(III) nitro chloride
- d) Pentaamminecobalt(III) nitrito chloride
40. Which of the following is a low-spin complex?
- a) [CoF₆]³⁻
- b) [Co(CN)₆]³⁻
- c) [Co(H₂O)₆]³⁺
- d) [Co(NH₃)₆]³⁺
41. What is the color of [CrF₆]³⁻?
- a) Green
- b) Violet
- c) Yellow
- d) Blue
42. Which of the following is a high-spin complex?
- a) [Co(CN)₆]³⁻
- b) [CoF₆]³⁻
- c) [Co(NH₃)₆]³⁺
- d) [Co(en)₃]³⁺
43. What is the geometry of [Ni(CO)₄]?
- a) Tetrahedral
- b) Square planar
- c) Octahedral
- d) Linear
44. Which of the following is an example of a geometric isomer?
- a) [Co(NH₃)₅Cl]²⁺
- b) [Pt(NH₃)₂Cl₂]
- c) [Co(en)₃]³⁺
- d) [Fe(CN)₆]⁴⁻
45. What is the name of the complex [Cr(H₂O)₄Cl₂]Cl?
- a) Tetrachlorodiaquachromium(III) chloride
- b) Dichlorotetraaquachromium(III) chloride
- c) Tetraaquadichlorochromium(III) chloride
- d) Dichlorotetraaquachromium(II) chloride
46. Which of the following is an example of an optical isomer?
- a) [Co(NH₃)₅Cl]²⁺
- b) [Co(en)₃]³⁺
- c) [Pt(NH₃)₂Cl₂]
- d) [Fe(CN)₆]⁴⁻
47. What is the color of [Cr(H₂O)₆]³⁺?
- a) Green
- b) Violet
- c) Yellow
- d) Blue
48. Which of the following is a low-spin complex?
- a) [CoF₆]³⁻
- b) [Co(CN)₆]³⁻
- c) [Co(H₂O)₆]³⁺
- d) [Co(NH₃)₆]³⁺
49. What is the name of the complex [Co(NH₃)₄Cl₂]Cl?
- a) Tetraamminedichlorocobalt(III) chloride
- b) Dichlorotetraamminecobalt(III) chloride
- c) Tetraamminecobalt(III) dichloride
- d) Dichlorotetraamminecobalt(II) chloride
50. Which of the following is a chelating agent?
- a) NH₃
- b) H₂O
- c) EDTA
- d) Cl⁻
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