CUET Chemistry Set-4: Coordination & Compounds
Question 1
The IUPAC name of the complex $\mathrm{[Co(en)_2Cl_2]Cl}$ is
(1) dichloridobis(ethane-1,2-diamine)cobalt(III) chloride
(2) bis(ethane-1,2-diamine)dichloridocobalt(II) chloride
(3) dichloridobis(ethylenediamine)cobalt(III) chloride
(4) bis(ethylenediamine)dichloridocobalt(III) chloride
Show Answer
Answer: (1)
Solution: en = ethane-1,2-diamine; ligands in alphabetical order, Co oxidation state +3, anion Cl⁻ outside sphere.
Question 2
Which of the following is NOT a chelating ligand?
(1) oxalate
(2) glycinate
(3) ethylenediamine
(4) ammonia
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Answer: (4)
Solution: NH₃ is monodentate; others have two donor atoms forming rings.
Question 3
The coordination number of Pt in $\mathrm{[PtCl_4]^{2-}}$ is
(1) 2
(2) 4
(3) 6
(4) 8
Show Answer
Answer: (2)
Solution: Four Cl⁻ ligands give CN = 4.
Question 4
The hybridisation of Fe in $\mathrm{[Fe(CN)_6]^{3-}}$ is
(1) $\mathrm{sp^3}$
(2) $\mathrm{sp^3d^2}$
(3) $\mathrm{d^2sp^3}$
(4) $\mathrm{dsp^3}$
Show Answer
Answer: (3)
Solution: CN⁻ is strong field → low spin; inner orbital octahedral complex.
Question 5
Which complex ion is diamagnetic?
(1) $\mathrm{[Cu(NH_3)_4]^{2+}}$
(2) $\mathrm{[Ni(CN)_4]^{2-}}$
(3) $\mathrm{[Fe(H_2O)_6]^{3+}}$
(4) $\mathrm{[CoF_6]^{3-}}$
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Answer: (2)
Solution: $\mathrm{[Ni(CN)_4]^{2-}}$ is square-planar, $\mathrm{d^8}$, all electrons paired.
Question 6
The EAN of Co in $\mathrm{[Co(NH_3)_6]^{3+}}$ is
(1) 33
(2) 36
(3) 35
(4) 34
Show Answer
Answer: (2)
Solution: Co(27) – 3 + 12 = 36 (Kr configuration).
Question 7
The number of geometrical isomers possible for $\mathrm{[Pt(NH_3)_2Cl_2]}$ is
(1) 1
(2) 2
(3) 3
(4) 4
Show Answer
Answer: (2)
Solution: Square-planar complex shows cis & trans forms.
Question 8
Which statement is WRONG about crystal-field theory?
(1) $\mathrm{t_{2g}}$ orbitals are stabilised in an octahedral field
(2) $\mathrm{e_g}$ orbitals are destabilised
(3) $\Delta_{\mathrm{o}}$ increases with ligand field strength
(4) $\Delta_{\mathrm{o}}$ is larger for 3d than for 4d metals
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Answer: (4)
Solution: 4d/5d metals give larger $\Delta_{\mathrm{o}}$ due to greater orbital extension.
Question 9
The colour of $\mathrm{[Ti(H_2O)_6]^{3+}}$ is due to
(1) d–d transition
(2) charge transfer
(3) ligand transition
(4) f–f transition
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Answer: (1)
Solution: Single d electron promotes from $\mathrm{t_{2g}}$ to $\mathrm{e_g}$.
Question 10
The ligand field strength order is
(1) $\mathrm{I^- < Br^- < Cl^- < F^- < H_2O < NH_3 < CN^-}$
(2) $\mathrm{F^- < Cl^- < Br^- < I^- < H_2O < NH_3 < CN^-}$
(3) $\mathrm{CN^- < NH_3 < H_2O < F^- < Cl^- < Br^- < I^-}$
(4) $\mathrm{I^- < Br^- < Cl^- < CN^- < NH_3 < H_2O}$
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Answer: (1)
Solution: Spectrochemical series places CN⁻ strongest, halides weakest.
Question 11
Which complex shows optical isomerism?
(1) $\mathrm{[Co(en)_3]^{3+}}$
(2) $\mathrm{[Co(NH_3)_4Cl_2]^+}$
(3) $\mathrm{[Pt(NH_3)_2Cl_2]}$
(4) $\mathrm{[Fe(CN)_6]^{3-}}$
Show Answer
Answer: (1)
Solution: Tris-chelate gives chiral octahedral arrangement.
Question 12
The magnetic moment of $\mathrm{[MnCl_4]^{2-}}$ (tetrahedral) is closest to
(1) 1.7 BM
(2) 2.8 BM
(3) 5.9 BM
(4) 4.9 BM
Show Answer
Answer: (3)
Solution: Mn²⁺ $\mathrm{d^5}$, high spin; 5 unpaired electrons, $\sqrt{35}$ ≈ 5.9 BM.
Question 13
In the complex $\mathrm{[Cr(C_2O_4)_3]^{3-}}$, the denticity of oxalate is
(1) 1
(2) 2
(3) 3
(4) 4
Show Answer
Answer: (2)
Solution: Oxalate is bidentate via two O atoms.
Question 14
The oxidation state of Ni in $\mathrm{[Ni(CO)_4]}$ is
(1) 0
(2) +2
(3) +4
(4) –2
Show Answer
Answer: (1)
Solution: CO is neutral ligand; Ni is in zero oxidation state.
Question 15
Which pair represents linkage isomers?
(1) $\mathrm{[Co(NH_3)_5NO_2]Cl_2}$ and $\mathrm{[Co(NH_3)_5ONO]Cl_2}$
(2) $\mathrm{[Co(NH_3)_4Cl_2]Cl}$ and $\mathrm{[Co(NH_3)_5Cl]Cl_2}$
(3) $\mathrm{[Cr(H_2O)_5SCN]^{2+}}$ and $\mathrm{[Cr(H_2O)_5NCS]^{2+}}$
(4)
(1) and (3) both
Show Answer
Answer: (4)
Solution: NO₂⁻ & SCN⁻ can bind through different donor atoms.
Question 16
The crystal-field stabilisation energy (CFSE) for $\mathrm{[Fe(CN)_6]^{3-}}$ is
(1) –0.4 $\Delta_{\mathrm{o}}$
(2) –2.0 $\Delta_{\mathrm{o}}$
(3) –2.4 $\Delta_{\mathrm{o}}$
(4) –1.2 $\Delta_{\mathrm{o}}$
Show Answer
Answer: (2)
Solution: Low spin $\mathrm{d^5}$: $\mathrm{t_{2g}^5 e_g^0}$ → –2.0 $\Delta_{\mathrm{o}}$.
Question 17
The complex that is outer orbital is
(1) $\mathrm{[Fe(CN)_6]^{3-}}$
(2) $\mathrm{[Co(NH_3)_6]^{3+}}$
(3) $\mathrm{[FeF_6]^{3-}}$
(4) $\mathrm{[Cr(NH_3)_6]^{3+}}$
Show Answer
Answer: (3)
Solution: F⁻ is weak field → uses 4d orbitals, $\mathrm{sp^3d^2}$ hybridisation.
Question 18
The formula of potassium trioxalatoaluminate(III) is
(1) $\mathrm{K[Al(C_2O_4)_3]}$
(2) $\mathrm{K_3[Al(C_2O_4)_3]}$
(3) $\mathrm{K[Al(C_2O_4)_2]}$
(4) $\mathrm{K_2[Al(C_2O_4)_2]}$
Show Answer
Answer: (2)
Solution: Al³⁺ needs 3 oxalates; overall –3 charge balanced by 3 K⁺.
Question 19
Which statement is TRUE for tetrahedral complexes?
(1) CFSE is larger than for octahedral
(2) They always show optical activity
(3) Crystal-field splitting $\Delta_{\mathrm{t}} \approx \frac{4}{9} \Delta_{\mathrm{o}}$
(4) They are always low spin
Show Answer
Answer: (3)
Solution: $\Delta_{\mathrm{t}}$ is ~4/9 of $\Delta_{\mathrm{o}}$; generally high spin.
Question 20
The complex ion $\mathrm{[Cu(NH_3)_4]^{2+}}$ has a
(1) square-planar geometry
(2) tetrahedral geometry
(3) octahedral geometry
(4) distorted octahedral geometry
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Answer: (1)
Solution: $\mathrm{d^9}$ Cu²⁺ undergoes Jahn–Teller distortion → square-planar.
Question 21
The value of $\Delta_{\mathrm{o}}$ for $\mathrm{[Co(en)_3]^{3+}}$ is larger than for $\mathrm{[Co(NH_3)_6]^{3+}}$ because
(1) en is a stronger field ligand
(2) en causes chelate effect
(3) en increases CFSE
(4) all of these
Show Answer
Answer: (4)
Solution: Chelate ring stabilises complex and increases ligand field.
Question 22
The number of unpaired electrons in $\mathrm{[NiCl_4]^{2-}}$ (tetrahedral) is
(1) 0
(2) 1
(3) 2
(4) 4
Show Answer
Answer: (3)
Solution: Ni²⁺ $\mathrm{d^8}$, tetrahedral; two unpaired electrons in high-spin state.
Question 23
Which complex will have the highest molar conductivity?
(1) $\mathrm{[Co(NH_3)_3Cl_3]}$
(2) $\mathrm{[Co(NH_3)_4Cl_2]Cl}$
(3) $\mathrm{[Co(NH_3)_5Cl]Cl_2}$
(4) $\mathrm{[Co(NH_3)_6]Cl_3}$
Show Answer
Answer: (4)
Solution: Gives 4 ions in solution, highest number of free ions.
Question 24
The correct order of increasing magnetic moment is
(1) $\mathrm{[Fe(CN)_6]^{3-} < [Fe(H_2O)_6]^{3+} < [MnCl_4]^{2-}}$
(2) $\mathrm{[MnCl_4]^{2-} < [Fe(CN)_6]^{3-} < [Fe(H_2O)_6]^{3+}}$
(3) $\mathrm{[Fe(H_2O)_6]^{3+} < [Fe(CN)_6]^{3-} < [MnCl_4]^{2-}}$
(4) $\mathrm{[Fe(CN)_6]^{3-} < [MnCl_4]^{2-} < [Fe(H_2O)_6]^{3+}}$
Show Answer
Answer: (1)
Solution: 1 < 5 < 5 unpaired electrons respectively.
Question 25
The complex $\mathrm{[Fe(CO)_5]}$ obeys the 18-electron rule. The number of CO ligands is
(1) 4
(2) 5
(3) 6
(4) 3
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Answer: (2)
Solution: Fe(8) + 5×2 = 18 electrons; hence 5 CO ligands.
BETA
