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Questions:

Case Study Questions

5 x 4 = 20

Read the passage given below and answer the following questions:
Valence bond theory considers the bonding between the metal ion and the ligands as purely covalent. On the other hand, crystal field theory considers the metal-ligand bond to be ionic arising from electrostatic interaction between the metal ion and the ligands. In coordination compounds, the interaction between the ligand and the metal ion causes the five d-orbitals to split-up. This is called crystal field splitting and the energy difference between the two sets of energy level is called crystal field splitting energy. The crystal field splitting energy (Δ_o) depends upon the nature of the ligand. The actual configuration of complexes is divided by the relative values of Δ_o and P (pairing energy)
If Δ_o < P, then complex will be high spin.
If Δ_o > P, then complex will be low spin.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following ligand has lowest Δ_o value?

(a) CN^-

(b) CO

(c) F^-

(d) NH₃

(ii) The crystal field splitting energy for octahedral (Δ_o) and tetrahedral (Δ_t) complex is related as

(a) \( \Delta_{t}=\frac{1}{2} \Delta_{o}\)	(b) \(\Delta_{t}=\frac{4}{9} \Delta_{o}\)
(c) \(\Delta_{t}=\frac{3}{5} \Delta_{o}\)	(d) \(\Delta_{t}=\frac{2}{5} \Delta_{o}\)

(iii) On the basis of crystal field theory, the electronic configuration of d⁴ in two situations: (i) Δ_o > P and (ii) Δ_o< P are

(i)	(ii)
(a) \(t_{2 g}^{4} e_{g}^{0}\)	\(t_{2 g}^{3} e_{g}^{1}\)
(b) \(t_{2 g}^{3} e_{g}^{1}\)	\(t_{2 g}^{4} e_{g}^{0}\)
(c) \(t_{2 g}^{3} e_{g}^{1}\)	\(t_{2 g}^{3} e_{g}^{1}\)
(d) \(t_{2 g}^{4} e_{g}^{0}\)	\(t_{2 g}^{4} e_{g}^{0}\)

(iv) Using crystal field theory, calculate magnetic moment of central metal ion of [FeF₆]^4-.

(a) 1.79 B.M.

(b) 2.83 B.M.

(c) 3.85 B.M.

(d) 4.9 B.M.

Read the passage given below and answer the following questions:
To explain bonding in coordination compounds various theories were proposed. One of the important theory was valence bond theory. According to that, the central metal ion in the complex makes available a number of empty orbitals for the formation ofcoordination bonds with suitable ligands. The appropriate atomic orbitals of the metal hybridise to give a set of equivalent orbitals of definite geometry. The d-orbitals involved in the hybridisation may be either inner d-orbitals i.e., (n - 1) d or outer d-orbitals i.e., nd. For example, CO³⁺ forms both inner orbital and outer orbital complexes, with ammonia it forms [Co(NH₃)₆]³⁺ and with fluorine it forms [CoF₆]^3- complex ion.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following is not true for [CoF₆]^3- ?

(a) It is paramagnetic.	(b) It has coordination number of 6.
(c) It is outer orbital complex.	(d) It involves d²sp³ hybridisation.

Which of the following is true for [Co(NH₃)₆]³⁺?

(a) It is an octahedral, dimagnetic and outer orbital complex.

(b) It is an octahedral, paramagnetic and outer orbital complex.

(c) It is an octahedral, paramagnetic and inner orbital complex.

(d) It is an octahedral, dimagnetic and inner orbital complex.

(iii) The paramagnetism of [CoF₆]^3- is due to

(a) 3 electrons

(b) 4 electrons

(c) 2 electrons

(d) 2 electrons

(iv) Which of the following is an inner orbital or low spin complex?

(a) \(\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\)

(b)\(\left[\mathrm{FeF}_{6}\right]^{3-}\)

(c) \(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}\)

(d) \(\left[\mathrm{NiCl}_{4}\right]^{2-}\)

Read the passage given below and answer the following questions:
Iron forms many complexes in its +2 and +3 oxidation states such as \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}(A) ;\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}(B)\) \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}(C) ;\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}(D)\) ,etc., They exhibit, different magnetic properties and undergo different hybridisation of iron.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following statements is correct?

(a) (B) is paramagnetic while (C) is diamagnetic.

(b) Both (B) and (D) are outer orbital complexes.

(c) Both (A) and (C) are paramagnetic.

(d) (A) is outer orbital complex and (C) is inner orbital complex.

(ii) The complex having maximum magnetic moment is

(a) (A)

(b) (B)

(c) (C)

(d) (D)

(iii) The spin only magnetic moment of complexes (A), (B), (C) and (D) are respectively (in BM)

(a) \(2 \sqrt{6}, 0, \sqrt{35}, \sqrt{3}\)

(b) \(0,2 \sqrt{6}, \sqrt{35}, \sqrt{3}\)

(c) \(\sqrt{15}, 2 \sqrt{6}, \sqrt{3}, 0\)

(d) \(\sqrt{3}, \sqrt{8}, 0, \sqrt{15}\)

(iv) Which of the given complexes are outer orbital complexes?

(a) (A) and (B) only

(b) (B) and (C) only

(c) (A) and (C) only

(d) (B) and (D) only

Read the passage given below and answer the following questions:
Coordination compounds are formulated and named according to the IUPAC system.
Few rules for naming coordination compounds are:
(I) In ionic complex, the cation is named first and then the anion.
(II) In the coordination entity, the ligands are named first and then the central metal ion.
(III) When more than one type of ligands are present, they are named in alphabetical order of preference without any consideration of charge.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The IUPAC name of the complex \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Br}\left(\mathrm{NO}_{2}\right) \mathrm{Cl}\right] \mathrm{Cl}\) is

(a) triamminechlorobromonitroplatinum (IV) chloride

(b) triamminebromonitrochloroplatinum (IV) chloride

(c) triamminebromidochloridonitroplatinum (IV) chloride

(d) triamminenitrochlorobromoplatinum (IV) chloride

(ii) The lUPAC name of [Ni(CO)₄] is

(a) tetracarbonylnickel (II)	(b) tetracarbonylnickel (0)
(c) tetracarbonylnickelate (II)	(d) tetracarbonylnickelate (0).

(iii) As per IUPAC nomenclature, the name of the complex \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{Cl}_{3}\) is

(a) tetraaquadiamminecobalt (II) chloride	(b) tetraaquadiamminecobalt (III) chloride
(c) diamminetetraaquacobalt (II) chloride	(d) diamminetetraaquacobalt (III) chloride

(iv) Which of the following represents correct formula of dichloridobis( ethane-1, 2-diamine ) cobalt (III) ion?

(a) [CoCl₂(en)]²⁺

(b) [Co(ONO)(NH₃)₅]SO₄

(c) [Co(NO₂)(NH₃)₄] (SO₄)₂

(d) [Co(NO)(NH₃)₄] (SO₄)₂

Read the passage given below and answer the following questions:
The molecular compounds which are formed from the combination of two or more simple stable compounds and retain their identity in the solid as well as in the dissolved state are called coordination compounds. Their properties are completely different from the constituents. In coordination compounds, the central metal atom or ion is linked to a number of ions or neutral molecules, called ligands, by coordinate bonds. For example, Dimethyl glyoxime (dmg) is a bidendate ligand chelating large amounts of metals. When dimethyl glyoxime is added to alcoholic solution of NiCl₂and ammonium hydroxide is slowly added to it, a rosy red precipitate of a complex is formed.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The structure of the complex is

(ii) Oxidation number of Ni in the given complex is

(a) +3

(b) +1

(c) +2

(d) zero.

(iii) Which of the following is true about this complex?

(a) It is paramagnetic, containing 2 unpaired electrons.

(b) It is paramagnetic, containing 1 unpaired electron.

(c) It is paramagnetic, containing 4 unpaired electrons.

(d) It is diamagnetic with no unpaired electron

(iv) Which one will give test for Fe³⁺ ions in the solution?

(a) [Fe(CN)₆]^3-	(b) [Fe(CN)₆]^2-
(c) (NH₄)₂SO₄· FeSO₄· 6H₂O	(d) Fe₂(SO₄)₃

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Answers Key:

Case Study Questions

5 x 4 = 20

(i) (c): Spectrochemical series:
\((\mathrm{I}^{-}<\mathrm{Br}^{-}<\mathrm{SCN}^{-}<\mathrm{Cl}^{-}<\mathrm{S}^{2-}<\mathrm{F}^{-}<\mathrm{OH}^{-}<\mathrm{C}_{2} \mathrm{O}_{4}^{2-}<\mathrm{O}^{2-}< \mathrm{H}_{2} \mathrm{O}<\mathrm{NCS}^{-}<\mathrm{EDTA}^{4-}<\mathrm{NH}_{3}\)(ii) (b)
(iii) (a) : When Δ_o > P, the electrons paired up in the t_2g level rather than going to the e_g level, so
when Δ_o> P : \(t_{2 g}^{4} e_{g}^{0}\)
and Δ_o < P : \(t_{2 g}^{3} e_{g}^{1}\)
(iv) (d): Fe²⁺: 3d⁶ ⇒\(t_{2 g}^{4} e_{g}^{2}\)
(Since, F^-is a weak field ligand)
Hence four unpaired electrons are present.
Magnetic moment (μ)\(=\sqrt{n(n+2)}=\sqrt{4(4+2)}=4.9 \mathrm{~B} \cdot \mathrm{M}\)

(i) (d): It involves sp³ d² hybridisation and not d²sp³.
(ii) (d) : [Co(NH3)₆]³⁺ is d²sp³hybridised with all electrons paired hence, it is diamagnetic and inner
orbital complex.

(iv) (c): Inner orbital complexes are formed with strong ligands as they force electrons to pair up and hence the complex will be either diamagnetic or will have less number of unpaired electrons.

(i) (c): (A) : sp³d² hybridisation (outer orbital)
No. of unpaired electrons = 4
(B) : d²sp³ hybridisation (inner orbital)
No. of unpaired electrons = 0
(C) : sp³ d² hybridisation (outer orbital)
No. of unpaired electrons = 5
(D) : d²sp³ hybridisation (inner orbital)
No. of unpaired electron = 1
(ii) (c): It has 5 unpaired electrons.
(iii) (a): Magnetic moments of (A), (B), (C) and (D) are respectively.
\(\sqrt{4(4+2)}, 0, \sqrt{5(5+2)}, \sqrt{1(1+2)}\)
(iv) (c)

(i) (c): Ligands are named in alphabetical order irrespective of their charge.
(ii) (b)
(iii) (d)
(iv) (d)

(ii) (c)
(iii) (d) : It has no unpaired electrons hence, it is diamagnetic.
(iv) (d): (a) and (b) are coordination compounds hence cannot give free Fe²⁺ or, Fe³⁺ ions in solution. (c) and (d) represent simple compounds hence are free to give ions in solution, but only Fe₂(SO₄)₃contains Fe³⁺ ions.(NH₄)₂SO_4・FeSO_4・ 6H₂O contains Fe²⁺ ions not Fe³⁺ ions.