Q1 · 2005-2021 · 2 marks
In the trigonal bipyramidal crystal field, the d orbital with the highest energy is
- (a) d_{xy}
- (b) d_{x^2-y^2}
- (c) d_{yz}
- (d) d_{z^2}
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Answer: (d)
GATE Chemistry (CY) — Coordination Chemistry previous year questions
36 questions · 2005 · all with verified answer · last checked 2026-11-06
Q2 · 2005-2021 · 2 marks
The pair of ions that most commonly forms complexes with coordination number 2 is
- (a) Cd (II) and Hg (II)
- (b) Cu (II) and Hg (I)
- (c) Cd (II) and Hg (I)
- (d) Cu (I) and Hg (II)
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Answer: (d)
Q3 · 2005-2021 · 2 marks
The set of ions expected to show Jahn-Teller distortion in their complexes is
- (a) Ti(III), Cu(II), High-spin Fe(III)
- (b) Cu(I), Ni(II), High-spin Fe(III)
- (c) Cu(II), Low-spin Fe(III), Ti(III)
- (d) Low-spin-Fe(III), Mn(II), Cu(I)
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Answer: (c)
Q4 · 2005-2021 · 2 marks
The CORRECT order of the rate of exchange of water molecules between the coordination sphere and the bulk is:
- (a) \mathrm{Cr^{3+} < Al^{3+} < Ni^{2+}}
- (b) \mathrm{Cr^{3+} < Al^{3+} < Ni^{2+} < Cr^{2+}}
- (c) \mathrm{Cr^{3+} < Ni^{2+} < Cr^{2+} < Al^{3+}}
- (d) \mathrm{Cr^{3+} < Cr^{2+} < Al^{3+} < Ni^{2+}}
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Answer: (b)
Q5 · 2005-2021 · 2 marks
The crystal structure of \mathrm{Pb}_{3}\mathrm{O}_{4} contains
- (a) octahedral and tetrahedra units
- (b) only octahedral units
- (c) octahedral and pyramidal units
- (d) octahedral and square-planar units
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Answer: (c)
Q6 · 2005-2021 · 2 marks
The compound which shows L \leftarrow M charge transfer is
- (a) \mathrm{Ni(CO)_4}
- (b) \mathrm{K_2Cr_2O_7}
- (c) HgO
- (d) [\mathrm{Ni(H_2O)_6}]^{2+}
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Answer: (a)
Q7 · 2005-2021 · 2 marks
The expected magnetic moments of the first – row transition metal complexes and those of the lanthanide metal complexes are usually calculated using
- (a) \mu_{\mathrm{s.o}} equation (s.o. = spin only) for both lanthanide and transition metal complexes
- (b) \mu_{\mathrm{s.o}} equation for lanthanide metal complexes and \mu_{J} equation for transition metal complexes
- (c) \mu_{\mathrm{s.o}} equation for transition metal complexes and \mu_{J} equation for lanthanide metal complexes
- (d) \mu_{L+S} equation for transition metal complexes and \mu_{\mathrm{s.o}} equation for lanthanide metal complexes
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Answer: (c)
Q8 · 2005-2021 · 2 marks
Designate the following complexes X, Y and Z as inert or labile:
\mathrm{X = [Al(C_2O_4)_3]^{3-}},\ \mathrm{Y = [V(H_2O)_6]^{2+}},\ \mathrm{Z = [Cr(C_2O_4)_3]^{3-}}
- (a) X and Y are inert; Z is labile
- (b) X and Z are labile; Y is inert.
- (c) X is inert; Y and Z are labile
- (d) X is labile; Y and Z are inert.
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Answer: (d)
Q9 · 2005-2021 · 2 marks
The number of unpaired electron(s) present in the species [\mathrm{Fe(H_2O)_5(NO)}]^{2+} which is formed during 'brown ring test' is:
- (a) 2
- (b) 3
- (c) 4
- (d) 5
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Answer: (b)
Q10 · 2005-2021 · 2 marks
\mathrm{Fe}_{3}\mathrm{O}_{4} and \mathrm{Co}_{3}\mathrm{O}_{4} are metal oxides having spinel structure. Considering their CFSEs, the correct statement regarding their structure is
- (a) both have normal spinel structure
- (b) both have inverse spinel structure
- (c) \mathrm{Fe}_{3}\mathrm{O}_{4} has normal and \mathrm{Co}_{3}\mathrm{O}_{4} has inverse spinel structure
- (d) \mathrm{Fe}_{3}\mathrm{O}_{4} has inverse and \mathrm{Co}_{3}\mathrm{O}_{4} has normal spinel structure
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Answer: (d)
Q11 · 2005-2021 · 2 marks
The d–d absorption band of \mathrm{[Fe(H_2O)_6]^{2+}} is split due to
- (a) presence of octahedral geometry
- (b) static Jahn–Teller distortion
- (c) dynamic Jahn–Teller distortion
- (d) presence of trigonal bipyramidal geometry
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Answer: (c)
Q12 · 2005-2021 · 2 marks
The crystal-field symbol for the ground-state of \left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{4-} is
- (a) {}^{2}\mathrm{T}_{2\mathrm{g}}
- (b) {}^{1}\mathrm{A}_{1\mathrm{g}}
- (c) {}^{5}\mathrm{E}_{\mathrm{g}}
- (d) {}^{6}\mathrm{A}_{1\mathrm{g}}
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Answer: (a)
Q13 · 2005-2021 · 2 marks
The complex that exists as a pair of enantiomers is
- (a) trans-[\mathrm{Co(H_2NCH_2CH_2NH_2)_2Cl_2}]^+
- (b) cis-[\mathrm{Co(NH_3)_4Cl_2}]^+
- (c) [\mathrm{Pt(PPh_3)(Cl)(Br)(CH_3)}]^-
- (d) [\mathrm{Co(H_2NCH_2CH_2NH_2)_3}]^{3+}
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Answer: (d)
Q14 · 2005-2021 · 2 marks
The increasing order of wavelength of absorption for the complex ions (i) [\mathrm{Cr(NH_3)_6}]^{3+} (ii) [\mathrm{CrCl_6}]^{3-} (iii) [\mathrm{Cr(OH_2)_6}]^{3+} (iv) [\mathrm{Cr(CN)_6}]^{3-}, is
- (a) iv < ii < i < iii
- (b) iv < iii < ii < i
- (c) iv < i < iii < ii
- (d) ii < iii < i < iv
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Answer: (c)
Q15 · 2005-2021 · 2 marks
The complex with inverse-spinel structure is
- (a) \mathrm{Co}_{3} \mathrm{O}_{4}
- (b) \mathrm{Fe}_{3} \mathrm{O}_{4}
- (c) \mathrm{MgAlO}_{4}
- (d) \mathrm{Mn}_{3} \mathrm{O}_{4}
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Answer: (b)
Q16 · 2005-2021 · 2 marks
The geometries of \mathrm{Ni(CO)_4} and \mathrm{[NiCl_4]^{2-}}, respectively, are
- (a) tetrahedral and square planar
- (b) square planar and tetrahedral
- (c) tetrahedral and tetrahedral
- (d) square planar and square planar
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Answer: (c)
Q17 · 2005-2021 · 2 marks
The complexes \mathrm{[Co(H_2O)_4Cl_2]NO_2} and \mathrm{[Co(H_2O)_4Cl(NO_2)]Cl} are
- (a) linkage isomers
- (b) positional isomers
- (c) ionization isomers
- (d) optical isomers
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Answer: (c)
Q18 · 2005-2021 · 2 marks
The number of microstates in term {}^{1}\mathrm{G} is ________
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Answer: 9
Q19 · 2005-2021 · 2 marks
Amongst the following, the complex ion that is expected to the highest magnetic moment at room temperature is
- (a) \left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}
- (b) \left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}
- (c) \left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}
- (d) \left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}
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Answer: (b)
Q20 · 2005-2021 · 2 marks
\mathrm{MnCr}_{2}\mathrm{O}_{4} is
- (a) normal spinel with total CFSE of -15.5\,\mathrm{Dq}
- (b) inverse spinel with total CFSE of -15.5\,\mathrm{Dq}
- (c) normal spinel with total CFSE of -24\,\mathrm{Dq}
- (d) inverse spinel with total CFSE of -24\,\mathrm{Dq}
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Answer: (c)
Q21 · 2005-2021 · 2 marks
The absorption spectrum of [\mathrm{Ti(H_2O)_6}]^{3+} in solution comprises of a maximum with a shoulder. The reason for the shoulder is
- (a) ligand-to-metal charge transfer (LMCT)
- (b) metal-to-ligand charge transfer (MLCT)
- (c) Jahn-Teller distortion
- (d) nephelauxetic effect.
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Answer: (c)
Q22 · 2005-2021 · 2 marks
The intense red color of \left[\mathrm{Fe}(\mathrm{bpy})_{3}\right]^{2+} (bpy =2,2' -bipyridine) is due to)
- (a) metal-to-ligand charge transfer (MLCT)
- (b) ligand-to-metal charge transfer (LMCT)
- (c) d-d transition
- (d) inter-valence charge transfer (IVCT)
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Answer: (a)
Q23 · 2005-2021 · 2 marks
The complexes \mathrm{K_2[NiF_6]} and \mathrm{K_3[CoF_6]} are
- (a) both paramagnetic
- (b) both diamagnetic
- (c) paramagnetic and diamagnetic, respectively
- (d) diamagnetic and paramagnetic, respectively
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Answer: (d)
Q24 · 2005-2021 · 2 marks
In the first row high-spin transition metal complexes \mathrm{[M(H_2O)_6]Cl_2} with \mathrm{d^5} and \mathrm{d^7} metal ions, the d-d transitions are
- (a) spin-forbidden for both
- (b) spin-allowed for both
- (c) spin-forbidden for \mathrm{d^5} and spin-allowed for \mathrm{d^7}
- (d) spin-allowed for \mathrm{d^5} and spin-forbidden for \mathrm{d^7}
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Answer: (c)
Q25 · 2005-2021 · 2 marks
According to Irving-Williams series, the number of d electrons for the first row transition metal (M) ion having the highest overall stability constant (\log \beta) for \mathrm{[M(EDTA)]^{2-}} is ____
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Answer: 9
Q26 · 2005-2021 · 2 marks
The spinel structure of \mathrm{MgAl_2O_4} has cubic close packed arrangement of oxide ions. The fractions of the octahedral and tetrahedral sites occupied by cations, respectively, are
- (a) 1/8 and 1/2
- (b) 1/4 and 1/2
- (c) 1/2 and 1/4
- (d) 1/2 and 1/8
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Answer: (d)
Q27 · 2005-2021 · 2 marks
The water exchange rates for the complex ions follow the order
- (a) \mathrm{[V(H_2O)_6]^{2+} > [Co(H_2O)_6]^{2+} > [Cr(H_2O)_6]^{3+}}
- (b) \mathrm{[Cr(H_2O)_6]^{3+} > [Co(H_2O)_6]^{2+} > [V(H_2O)_6]^{2+}}
- (c) \mathrm{[Co(H_2O)_6]^{2+} > [Cr(H_2O)_6]^{3+} > [V(H_2O)_6]^{2+}}
- (d) \mathrm{[Co(H_2O)_6]^{2+} > [V(H_2O)_6]^{2+} > [Cr(H_2O)_6]^{3+}}
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Answer: (d)
Q28 · 2005-2021 · 2 marks
The lowest energy \mathrm{d} \rightarrow \mathrm{d} transition of the complexes follow the order
- (a) [\mathrm{Cr(H_2O)_6}]^{3+} < [\mathrm{Cr(NH_3)_6}]^{3+} < [\mathrm{Cr(CN)_6}]^{3-}
- (b) [\mathrm{Cr(CN)_6}]^{3-} < [\mathrm{Cr(NH_3)_6}]^{3+} < [\mathrm{Cr(H_2O)_6}]^{3+}
- (c) [\mathrm{Cr(CN)_6}]^{3-} < [\mathrm{Cr(H_2O)_6}]^{3+} < [\mathrm{Cr(NH_3)_6}]^{3+}
- (d) [\mathrm{Cr(NH_3)_6}]^{3+} < [\mathrm{Cr(CN)_6}]^{3-} < [\mathrm{Cr(H_2O)_6}]^{3+}
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Answer: (a)
Q29 · 2005-2021 · 2 marks
The symmetry label of valence p orbitals of a metal ion in an octahedral ligand field is
- (a) t_{1g}
- (b) t_{1u}
- (c) e_g + a_{1g}
- (d) t_{2g}
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Answer: (b)
Q30 · 2005-2021 · 2 marks
Spectroscopic ground state term symbols of cobalt ions in \mathrm{[Co(H_2O)_6]^{2+}} and \mathrm{[CoCl_4]^{2-}} respectively are
- (a) {}^{2}T_{1g} and {}^{4}A_{2}
- (b) {}^{4}T_{1g} and {}^{4}A_{2}
- (c) {}^{4}T_{2g} and {}^{4}T_{1}
- (d) {}^{2}T_{1} and {}^{4}A_{1}
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Answer: (b)
Q31 · 2005-2021 · 2 marks
For an inverse spinel, \mathrm{AB_2O_4}, the A and B, respectively, can be
- (a) Ni(II) and Ga(III)
- (b) Zn(II) and Fe(III)
- (c) Fe(II) and Cr(III)
- (d) Mn(II) and Mn(III)
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Answer: (a)
Q32 · 2005-2021 · 2 marks
The reaction of \mathrm{NiBr}_{2} with two equivalents of \mathrm{PPh}_{3} in \mathrm{CS}_{2} at -78^{\circ} \mathrm{C} gives a red-colored diamagnetic complex. \left[\mathrm{NiBr}_{2}\left(\mathrm{PPh}_{3}\right)_{2}\right]. This transforms to a green-colored paramagnetic complex with the same molecular formula at 25^{\circ} \mathrm{C}. The geometry and the number of unpaired electrons in the green-colored complex, respectively, are:
- (a) square planar and 2
- (b) tetrahedral and 2
- (c) square planar and 4
- (d) tetrahedral and 1
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Answer: (b)
Q33 · 2005-2021 · 2 marks
The rate of the substitution reaction of \left[\mathrm{Co}(\mathrm{CN})_{5} \mathrm{Cl}\right]^{3-} with \mathrm{OH}^{-}to give \left[\mathrm{Co}(\mathrm{CN})_{5}(\mathrm{OH})\right]^{3-}
- (a) is inversely proportional to the concentration of \mathrm{OH}^{-} perchlorate ion, +7 , charge transfer
- (b) depends on the concentrations of both \left[\mathrm{Co}(\mathrm{CN})_{5} \mathrm{Cl}\right]^{3-} and \mathrm{OH}^{-} chromium chloride, +3 , d-d transition
- (c) depends on the concentration of \left[\mathrm{Co}(\mathrm{CN})_{5} \mathrm{Cl}\right]^{3-} only dichromate ion, +6 and +6 , charge transfer
- (d) is directly proportional to the concentration of \mathrm{OH}^{-}only HCl . The red-orange complex, the oxidation state of its central element(s), and the origin of its color, respec tively, are: chromic acid, +6 , charge transfer
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Answer: (c)
Q34 · 2005-2021 · 2 marks
The \Delta_{0} of \left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+},\left[\mathrm{CrF}_{6}\right]^{3-} and \left[\mathrm{Cr}(\mathrm{CN})_{6}{ }^{3-}\right. follows the order:
- (a) \left[\mathrm{CrF}_{6}\right]^{3-}>\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}>\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}
- (b) \left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}>\left[\mathrm{CrF}_{6}\right]^{3-}>\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}
- (c) \left[\mathrm{CrF}_{6}\right]^{3-}>\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}>\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}
- (d) \left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}>\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}>\left[\mathrm{CrF}_{6}\right]^{3-}
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Answer: (d)
Q35 · 2005-2021 · 2 marks
The spin-only magnetic moment of \left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+} (rounded off to one decimal place) is ____ BM.
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Answer: 3.9
Q36 · 2005-2021 · 2 marks
The correct order of increasing intensity (molar absorptivity) of the UV-visible absorption bands for the ions \left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+},\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+},\left[\mathrm{CrO}_{4}\right]^{2-}, and \left[\mathrm{NiCl}_{4}\right]^{2-} is
- (a) \left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}<\left[\mathrm{NiCl}_{4}\right]^{2-}<\left[\mathrm{CrO}_{4}\right]^{2-}<\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}
- (b) \left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}<\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}<\left[\mathrm{CrO}_{4}\right]^{2-}<\left[\mathrm{NiCl}_{4}\right]^{2-}
- (c) \left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}<\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}<\left[\mathrm{NiCl}_{4}\right]^{2-}<\left[\mathrm{CrO}_{4}\right]^{2-}
- (d) \left[\mathrm{NiCl}_{4}\right]^{2-}<\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}<\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}<\left[\mathrm{CrO}_{4}\right]^{2-} COORDINATION ANSWERS KEY
1. (a) 2. (d) 3. (a) 4. (d) 5. (b) 6. (b) 7. (d) 8. (c) 9. (c) 10. (a) 11. (b) 12. (c) 13. (b) 14. (a) 15. (c) 16. (d) 17. (d) 18. (a) 19. (d) 20 (b) 21. (d) 22. (c) 23. (b) 24. (c) 25. (?) 26. (b) 27. (?) 28. (d) 29. (b) 30. (d) 31. (a) 32. (c) 33. (a) 34. (?) 35. (?) 36. (d) 37. (d) 38. (b) 39. (c) 40. (c) 41. (b) 42. (b) 43. (d) 44. (c) 45. (c) 46. (c) 47. (c) 48. (9) 49. (a) 50. (b) 51. (c) 52. (c) 53. (a) 54. (d) 55. (d) 56. (c) 57. (c) 58. (9) 59. (2.0) 60. (d) 61. (b) 62. (c) 63. (c) 64. (d) 65. (d) 66. (a) 67. (b) 68. (b) 69. (a) 70. (?) 71. (?) 72. (?) 73. (?) 74. (?) 75. (2) 76. (a) 77. (b) 78. (c) 79. (?) 80. (d) 81. (3.9) 82. (c)
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Answer: (c)
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