Question Set A

cbse 12th Standard Chemistry Coordination Compounds Model Questions Papers Study Material - QB365

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Questions:

Generic 3

5 x 3 = 15

Explain the following terms giving a suitable example in each case:
(i) Ambident ligand
(ii) Denticity of a ligand

For the complex [Fe(en)₂Cl₂]Cl, identify the following:
(i) Oxidation number of iron.
(ii) Hybrid orbitals and shape of the complex.
(iii) Magnetic behavior of the complex.
(iv) Number of its geometrical isomers.
(v) Whether there may be optical isomer also.
(vi) Name of the complex.

Compare the following complexes with respect to their molecular shape and mahnetic behaviour:
(i) [Cr(NH₃)₆]³⁺
(ii) [Fe(CN)₆]^4-
(iii) [NiCl₄]^2-
(At. No:Cr = 24, Fe = 26, Ni = 28)

What do you understand by stepwise stability constant and overall stability constant of a coordination compound? How are these two constants related?

What type of isomerism is exhibited by [CO(NH₃)₄CI₂]⁺ Br^-? Write the structures of the possible isomers and the state of hybridisation of the central metal atom.

Multiple Choice Question

10 x 1 = 10

2 : 4 Dinitrophenyl hydrazine is an example for

(a)

Tridentate ligend

(b)

Monodentate ligand

(c)

Polydentate ligand

(d)

Didentate ligand

Which of the following is not considered as an organometallic compound?

(a)

cis-platin

(b)

ferrocene

(c)

Zeise's salt

(d)

Grignard reagent

The non-existent metal carbonyl among the following is

(a)

Cr(CO)₆

(b)

Mn(CO)₅

(c)

Ni(CO)₄

(d)

Fe(CO)₅

The correct structure of Fe(CO)₅ is

(a)

octahedral

(b)

terahedral

(c)

square pyramidal

(d)

trigonal bipyramidal

10.

Zelse's salt is

(a)

[Fe(C₅H₅)₂]

(b)

[Pb(C₂H₅)₄]

(c)

K[PtCl₃(C₂H₄)]

(d)

[Ni(CO)₄]

11.

Prussian blue is obtained by mixing together aqueous solution of Fe³⁺ salt with

(a)

Ferricyanide

(b)

Ferocyanide

(c)

Hydrogen cyanide

(d)

Sodium cyanide

12.

The dark blue colour of the solution formed when excess of ammonia is added to a solution of copper (II) sulphate is due to the presence of the ion

(a)

[Cu(OH)₄ (H₂O)₂]^2-

(b)

[Cu(H₂O)₆]²⁺

(c)

[Cu(NH₃)₂ (H₂O)₄]²⁺

(d)

[Cu(NH₃)₄ (H₂O)₂]²⁺

13.

The most stable complex among the following is

(a)

K₃[Al(C₂O₄)₃]

(b)

[Pt(en)₂] Cl₂

(c)

[Ag(NH₃)₂] Cl

(d)

K₂[Ni(EDTA)]

14.

Which of the following configuration of ions has zero CFSE in both strong and weak ligand fields?

(a)

d¹⁰

(b)

d⁸

(c)

d⁶

(d)

d⁴

15.

Which of the following compound has tetrahedral geometry?

(a)

[Ni(CN)₄]^2-

(b)

[Pd(CN)₄]^2-

(c)

[PdCl₄]^2-

(d)

[NiCl₄]^2-

Generic 2

10 x 2 = 20

16.

Account fpr different magnetic behaviour of hexacyanoferrate (III) and hexafluoroferrate (III).

17.

Arrange the following complexes in order of increasing electrical conductivity:
[Co(NH₃)₃Cl₃], [Co(NH₃)₅Cl]Cl₂, [Co(NH₃)₆] Cl₃, [Co(NH₃)₄Cl₂]Cl

18.

On the basis of valence bond theory, explain geometry, nature of hybridisation, magnetic property and optical isomerism of [Co(ox)₃]^3- and [CoF₆]^3-.

19.

A coordination compound has the formula, CoCl₃.4NH₃. It doesnot liberate ammonia but precipitates chloride ions as silver chloride. Give the IUPAC name of the complex and write its structural formula.

20.

Write the names and draw the structures of each of the following complex compounds:
(i) [Co(NH₃)₄(H₂O)₂]Cl₃
(ii) [Pt(NH₃)₄] [NiCl₄]

21.

Write the correct formulae for the following coordination compounds ;
(a) CrCl₃.6H₂O (violet, with 3 chloride ions/ unit formula)
(b) CrCl₃.6H₂O (light green colour with 2 chloride ions/ unit formula)
(c) CrCl₃.6H₂O (dark green colour with 1 chloride ion/ unit formula)

22.

Why only transition metals are known to form \(\pi \) complexes?

23.

Which of the following is more stable complex and why?
[Co(NH₃)₆]³⁺ and [Co(en)₃]³⁺

24.

\(Fe^{ 2+ }\overset { SCN^{ - } }{ \underset { { excess } }{ \rightarrow } } (A)\overset { { F }^{ - } }{ \underset { excess }{ \rightarrow } } (B)\)
What are (A) and (B)? Give IUPAC name of (A). Find the spin only magnetic moment of (B).

25.

Dimethyl glyoxime is added to alcoholic solution of NiCl₂. When ammonium hydroxide is slowly added to it, a rosy red precipitate of a complex appears
(i) Give the structure of the complex showing hydrogen bonds.
(ii) Give oxidation state and hybridisation of central metal ion.
(iii) Identify whether it is paramagnetic or diamagnetic.

Generic 5

3 x 5 = 15

26.

CoSO₄Cl.5 NH₃exists in two isomeric forms 'A' and 'B' gives white precipitate with BaCl₂but does not react with AgNO₃. Answer the following questions.
(i) Identify 'A' and 'B' and write their structure formulas.
(ii) Name the type of isomerism involved
(iii) Give the IUPAC name of 'A' and 'B'.

27.

Using valence bond theory, explain the following in relation to the complexes given below :
\([Mn(CN)_6]^{3-}, [Co(NH_3)_6]^{3+}, [Cr(H_2O)_6]^{3+}, [FeCl_6]^{4-}\)
(i) Type of hybridisation
(ii) Inner or outer orbital complex.
(iii) Magnetic behaviour.
(iv) Spin only magnetic moment value.

28.

Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).

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Answers Key:

Generic 3

5 x 3 = 15

(i) Ambidentate ligand: Ligands which can ligate (link) through two different atoms present in it are called ambidentate ligands, e.g.\({ { NO }_{ 2 } }^{ - },{ SCN }^{ - },{ CNO }^{ - },{ CN }^{ - },{ { NO }_{ 2 } }^{ - }\) can link through 'N' as well as oxygen while SCN^- can link through'S' as well as 'N' atom.
(ii) Denticity: The number of ligating (linking) atoms present in ligand is called denticity of a ligand, e.g.
CN^- has 1,\(\overset { { COO }^{ - } }{ \underset { { COO }^{ - } }{ | } } \) has 2,
H₂N-CH₂-CH₂-NH-CH₂-CH₂-NH₂ has 3.
H₂NCH₂CH₂NHCH₂CH₂NHCH₂CH₂NH₂ has 4.
[EDTA]^3- has 5, [EDTA]^4- has 6 denticity.

(i) +3 (III)
(ii) dsp, octahedral
(iii) paramagnetic
(iv) Two geometrical isomers
(v) Yes, there may be optical isomer also due to presence of polydentate ligand.
(vi) Dichlorido bis-(ethane 1, 2-diamine) Iron (III)

(i) In [Cr(NH₃)₆]³⁺
Cr(24): [Ar]4s¹3d⁵
Cr³⁺: [Ar]4s⁰3d³
(ii)

[CN^- being strong field ligand, paired up the d-electrons of the metal].

Shape Octahedral
Magnetic property Diamagnetic.

Complexes are formed from aqueous solution and the reaction involves the replacement of water molecules by the ligands in various steps, each step having its formation constant, e.g.
[CU(H₂O)₄]SO₄ + 4NH₃ \(\overset { K }{ \rightleftharpoons } \) [Cu(NH₃)₄]SO₄ + 4H₂O
1st step: [CU(H₂O)₄]SO₄ + NH₃ \(\overset { { K }_{ 1 } }{ \rightleftharpoons } \) [CU(H₂O)₃NH₃] SO₄ + H₂O
2nd step: [Cu(H₂O)₃NH₃]SO₄ + NH₃ \(\overset { { K }_{ 2 } }{ \rightleftharpoons } \) [CU(H₂O)₂(NH₃)₂] + H₂O
3rd step: [CU(H₂O)₂(NH₃)₂]SO₄ + NH₃ \(\overset { { K }_{ 3 } }{ \rightleftharpoons } \) [Cu(H₂O)(NH₃)₃] + H₂O
4th step: [Cu(H₂O)(NH₃)₃]SO₄ + NH₃ \(\overset { { K }_{ 4 } }{ \rightleftharpoons } \) [Cu(NH₃)₄]SO₄ + H₂O
K= k₁ x k₂ x k₃ x k₄

Ionisation isomerism and Geometrical isomerism are exhibited by [CO(NH₃)₄CI₂] Br.
The ionisation isomers are [CO(NH₃)₄CI₂] Br and [CO(NH₃)₄(CI)(Br)CI.
The geometrical isomers are

The central atom has d²sp³ hybridisation.

Multiple Choice Question

10 x 1 = 10

(b)
Monodentate ligand

(b)
ferrocene

(b)
Mn(CO)₅

10.

11.

(b)
Ferocyanide

12.

(d)
[Cu(NH₃)₄ (H₂O)₂]²⁺

13.

(d)
K₂[Ni(EDTA)]

14.

(a)
d¹⁰

15.

(d)
[NiCl₄]^2-

Generic 2

10 x 2 = 20

16.

In [Fe(CN )₆]^3- , CN^- is a strong ligand. Hence, electrons in the d-subshell pair up and there is only one unpaired electron left.In [FeF₆]^3- ,is a weak ligand. Hence, electrons in the 3 d subshell do not pair up. There are five unpaired electrons in the 3d-subshell. (The hybridization involved is sp³d² _ outer orbital complex is formed). Hence, [FeF₆ ]^3- has greater magnetic moment than [Fe(CN ]^3- .

17.

[Co(NH₃)₃Cl₃] < [Co(NH₃)₄Cl₂]Cl < [Co(NH₃)₅Cl]Cl₂< [Co(NH₃)₆] Cl₃. This is because number of ions produced from these complexes are 0,2,3 and 4 respectively.

18.

[Co(ox)₃]^3-: Geometry = octahedral, Hybridisation = sp³d², Magnetic properties = paramagnetic. Two optical isomers.
[CoF₆]^3-: Geometry = octahedral, Hybridisation = sp³d², Magnetic properties = paramagnetic. No optical isomers.

19.

Remembering that coordination number of Co is 6, the formula of the complex will be [Co(NH₃)₄Cl₂] Cl. The name will be tetraamminedichloridocobalt (III) chloride.

20.

21.

(a) [Cr(H₂O)₆Cl₃ (b) [Cr(H₂O)₅Cl]Cl₂.H₂O (c) [Cr(H₂O)₄Cl₂]Cl.2H₂O
Note that coordination number of Cr is 6 in each case.

22.

Transition metals/ions have empty d-orbitals into which the electron-pairs can be donated by ligands containing \(\pi \) electrons, i.e., CH₂ = CH₂, C₅H₅, C₆H₆, etc.

23.

[Co(en)₃]³⁺is more stable due to chelate effect of the bidentate ligand, en, as it forms rings.

24.

(A) = Fe(SCN)₃, (B) = [FeF₆]^3- .
IUPAC name of A = trithiocyanatoiron (Ill)
E.C. of Fe (III) = d⁵. Unpaired electrons = 5
Spin only magnetic moment = \(\sqrt { 5(5+2) } \) = 5·916 BM.

25.

(ii) Oxidation state of Ni in the complex = + 2
Hybridisation = dsp² (because it is a planar molecule)
(iii) It is diamagnetic (because there is no unpaired electron present)

Generic 5

3 x 5 = 15

26.

(i) As isomer A reacts with AgNO₃ to give a white precipitate, CI must be present in the ionization sphere. As it does not react with BaCI₂, SO₄^2- must be present in coordination sphere.
Formula of A = [Co(NH₃)₅SO₄] CI (coordination no. of Co = 6) As reactions are reverse for isomer B, formula of B = [Co(NH₃)₅CI]S0₄
(ii) Ionization isomerism.
(iii) A = Pentaarnminesulphatocobalt (III) chloride ; B = Pentaamminechloridocobalt (ill) sulphate

27.

\([Mn(CN)_6]^{3-}\)
d²sp³, (ii) inner orbital complex, (iii) paramagnetic, (iv) 2.87 B.M.
(i) d²sp³ (ii) Inner orbital complex, (iii) diamagnetic, (iv) \(\mu=0\)
(i) d²sp³, (ii) Inner orbital complex, (iii) paramagnetic, (iv) 3.87 B.M.
(i) sp³d², (ii) outer orbital complex (iii) paramagnetic (iv) 4.9 B.M.

28.

(i) \([CoF_6]^{3-}\)
\( [Co(H_2O)_6]^{2+}\)
\([Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}\)
\(\ [Fe(H_2O)_6]^{2+}\)
\([Fe(CN)_6]^{4-}\)
It is diamagnetic due to the absence of unpaired electrons.