Coordination Compounds: Class 12 Important Questions with Answers

Practice set: test yourself

Try every question before looking at the answers below. 64 or more out of 80 means you are ready for the board.

C. Very short answer (1 mark each)

1. Define a ligand.
2. What is a chelate?
3. Name [Ni(CO)₄].
4. Formula of potassium hexacyanidoferrate(II).
5. Oxidation state of Cu in [Cu(CN)₄]³⁻.
6. What is linkage isomerism?
7. Why is CO a strong ligand?
8. Define pairing energy.
9. Give one biological complex.
10. What is a homoleptic complex?

D. Short answer I (2 marks each)

1. Name: (a) [Co(NH₃)₅Cl]Cl₂ (b) K₂[Ni(CN)₄].
2. Write the formulae: (a) tetraamminecopper(II) sulphate (b) potassium tetrachloridoplatinate(II).
3. Moles of AgCl from CoCl₃·5NH₃? Structure?
4. Draw cis and trans [Pt(NH₃)₂Cl₂].
5. Calculate μ for [Fe(H₂O)₆]³⁺.
6. Why is [Ti(H₂O)₆]³⁺ violet?
7. Give the d⁶ configurations for Δo > P and Δo < P.
8. Distinguish inner and outer orbital complexes.

Rough work

E. Short answer II (3 marks each)

1. Explain the hybridisation, shape and magnetism of [Co(NH₃)₆]³⁺ (VBT).
2. Draw the octahedral splitting diagram and explain Δo.
3. Explain linkage, ionisation and coordination isomerism with one example each.
4. Why is [NiCl₄]²⁻ paramagnetic but [Ni(CN)₄]²⁻ diamagnetic?
5. Write IUPAC names: [Cr(en)₃]Cl₃, [Pt(NH₃)₄][PtCl₄], K₃[Al(C₂O₄)₃].
6. Give three applications of coordination compounds.

F. Long answer (5 marks each)

1. (a) State the postulates of Werner's theory. (b) CoCl₃·4NH₃ gives 1 mol AgCl. Write its structure and name. (c) How many geometrical isomers does it have?
2. (a) Compare VBT and CFT for [Fe(CN)₆]³⁻ and [FeF₆]³⁻. (b) Explain why tetrahedral complexes are high spin. (c) Arrange [Co(H₂O)₆]³⁺, [Co(NH₃)₆]³⁺, [Co(CN)₆]³⁻ by Δo.

G. HOTS (higher-order thinking)

1. Why is [Co(NH₃)₆]³⁺ yellow-orange but [CoF₆]³⁻ blue?
2. Why does [Cu(NH₃)₄]²⁺ form a deep blue colour from pale blue [Cu(H₂O)₄]²⁺?
3. Why can't [Ni(NH₃)₆]²⁺ be an inner orbital complex?
4. Why is the cis isomer of [Pt(en)₂Cl₂]²⁺ optically active but not the trans?

20 MCQs

1. CN of Fe in [Fe(C₂O₄)₃]³⁻
   (a) 3 (b) 4 (c) 6 (d) 9
2. Ambidentate ligand
   (a) SCN⁻ (b) NH₃ (c) en (d) H₂O
3. Hybridisation of [Ni(CN)₄]²⁻
   (a) sp³ (b) sp³d² (c) d²sp³ (d) dsp²
4. Unpaired electrons in [CoF₆]³⁻
   (a) 0 (b) 4 (c) 2 (d) 5
5. Strongest field ligand
   (a) H₂O (b) CO (c) Cl⁻ (d) NH₃
6. Oxidation state of Pt in [PtCl₂(en)₂]²⁺
   (a) +2 (b) 0 (c) +6 (d) +4
7. Moles of AgCl from [Co(NH₃)₅Cl]Cl₂
   (a) 2 (b) 1 (c) 3 (d) 0
8. Optically active
   (a) trans-[CoCl₂(en)₂]⁺ (b) [Pt(NH₃)₂Cl₂] (c) [Co(en)₃]³⁺ (d) [Ni(CO)₄]
9. Geometry of [Ni(CO)₄]
   (a) square planar (b) linear (c) octahedral (d) tetrahedral
10. Highest conductivity
    (a) [Co(NH₃)₃Cl₃] (b) [Co(NH₃)₆]Cl₃ (c) [Co(NH₃)₄Cl₂]Cl (d) [Co(NH₃)₅Cl]Cl₂
11. Configuration of d⁶ with Δo > P
    (a) t₂g⁴e_g² (b) t₂g³e_g³ (c) t₂g⁶ (d) t₂g⁵e_g¹
12. Chelating ligand
    (a) C₂O₄²⁻ (b) Cl⁻ (c) NH₃ (d) CN⁻
13. Used against lead poisoning
    (a) cis-platin (b) EDTA (c) DMG (d) en
14. [Co(NH₃)₅NO₂]²⁺ and [Co(NH₃)₅ONO]²⁺ are
    (a) ionisation (b) coordination (c) linkage (d) optical isomers
15. Name of [Fe(CN)₆]³⁻
    (a) hexacyanidoiron(III) (b) ferricyanide(II) (c) hexacyanoiron(II) (d) hexacyanidoferrate(III)
16. Colourless complex
    (a) [Zn(H₂O)₆]²⁺ (b) [Ti(H₂O)₆]³⁺ (c) [Cu(H₂O)₄]²⁺ (d) [Ni(H₂O)₆]²⁺
17. Geometrical isomers of [Co(NH₃)₃Cl₃]
    (a) 2 (b) 1 (c) 3 (d) 4
18. e_g orbitals in an octahedral field
    (a) dxy, dyz (b) all five (c) dxz, dyz (d) d(x²−y²), d(z²)
19. Mond process refines
    (a) Fe (b) Ni (c) Cu (d) Ag
20. μ of [Mn(CN)₆]⁴⁻
    (a) 5.92 (b) 3.87 (c) 1.73 (d) 0

1 (c) · 2 (a) · 3 (d) · 4 (b) · 5 (b) · 6 (d) · 7 (a) · 8 (c) · 9 (d) · 10 (b) · 11 (c) · 12 (a) · 13 (b) · 14 (c) · 15 (d) · 16 (a) · 17 (a) · 18 (d) · 19 (b) · 20 (c)

Assertion–Reason (6)

(a) Both true, R explains A. (b) Both true, R does not explain A. (c) A true, R false. (d) A false, R true.

1. A: [Ni(CO)₄] is diamagnetic. R: CO pairs the electrons of Ni.
2. A: Tetrahedral complexes are generally high spin. R: Δt is smaller than the pairing energy.
3. A: [Co(NH₃)₃Cl₃] gives 3 mol AgCl. R: It has three Cl atoms.
4. A: [Fe(C₂O₄)₃]³⁻ is more stable than [FeCl₆]³⁻. R: Oxalate forms chelate rings.
5. A: Cu²⁺ salts are coloured. R: Cu²⁺ has a d⁹ configuration.
6. A: CO is a weak field ligand. R: CO forms σ and π bonds with the metal.

Key: 1 (a) · 2 (a) · 3 (d) · 4 (a) · 5 (a) · 6 (d)

Answers to the practice set