MCQs on Crystal Field Theory

Crystal Field Theory (CFT) explains the interaction of metals and ligands in a coordination compound. It explains the structure, colour, formation and magnetic properties of coordination compounds. According to this the metal-ligand bonds are electrostatic and formed between metal cations and negatively charged ligands. The ligand causes splitting of degenerate orbitals into two groups having different energies. In the octahedral environment, the crystal field splitting results in the formation of lower energy dxy dyz and dxz orbitals known as t2g orbitals and dx2-y2 and dz2 with higher energy known as eg orbitals. Crystal field theory explains that the colour of coordination compounds is due to d-d transition of electrons.

1. Which of the following complexes shows zero crystal field stabilization energy?

(a) [Co(H2O)6]3+

(b) [Fe(H2O)6]3+

(c) [Co(H2O)6]2+

(d) [Mn(H2O)6]3+

Answer: (b)

2. Which of the following is paramagnetic?

(a) [CoBr]42-

(b) Mo(Co)6

(c) [Pt(en)Cl2]

(d) [Co(NH3)6]3+

Answer: (a)

3. For a high spin d4 octahedral complex the crystal field splitting energy will be

(a) -1.6 Δo

(b) -0.8 Δo

(c) -0.6 Δo

(d) -1.2 Δo

Answer: (c)

4. Which of the following is a bidentate ligand?

(a) Br

(b) CH3NH2

(c) C2O42-

(d) CH3CN

Answer: (c)

5. How many unpaired electrons are present in [CoF6]3- complex?

(a) 4

(b) zero

(c) 2

(d) 3

Answer: (a)

6. Which of the following d orbitals take part in the octahedral complex with d2sp3 hybridisation?

(a) dxy, dyz

(b) dxz, dx2−y2

(c) dx2−y2, dz2

(d) dz2, dxz

Answer: (c)

7. The compound, which does not contain a metal-carbon bond is

(a) K[Pt(C2H4)Cl3]

(b) C2H5MgBr

(c) Ni(CO)4

(d) Al(OC2H5)3

Answer: (d)

8. The correct increasing order of splitting power of ligands according to spectrochemical series is

(a) Cl < OH < CN

(b) Cl < CN < OH

(c) OH < Cl < CN

(d) OH < CN < Cl

Answer: (a)

9. Which of the following complexes has a magnetic moment of 1.73 BM?

(a) [Ni(CN)4]2-

(b) TiCl4

(c) [Cu(NH3)4]2+

(d) [CoCl6]4-

Answer: (c)

10. Tetraamminecopper(II) sulphate is _______ in colour.

(a) violet

(b) blue

(c) green

(d) red

Answer: (b)

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