CBSE Class 12 Chemistry Coordination Compounds VBQs

Question. A co-ordination complex compound of cobalt has the molecular formulae containing five ammonia molecules, one nitro group and two chlorine atoms for one cobalt atom. One mole of this compound produces three mole ions in an aqueous solution on reacting with excess of AgNO₃, AgCl precipitate. The ionic formula for this complex would be:
a. [Co (NH₃)₅ (NO₂)] Cl₂
b. [Co(NH₃)₅ Cl] [Cl(NO₂)]
c. [Co(NH₃) (No₂)Cl][(NH₃)Cl]
d. [Co(NH₃)₅ ][(NO₂)₂ Cl₂]
Answer : A

Question. Prussian blue is formed when:
a. Ferrous sulphate reacts with FeCl₃
b. Ferric sulphate reacts with K₄ [Fe (CN)₆]
c. Ferrous ammonium sulphate reacts with FeCl₃
d. Ammonium sulphate reacts with FeCl₃
Answer : B

Question. Silver sulphide dissolved in a solution of sodium cynamide to form the complex:
a. Na [Ag (CN)₂]
b. Na₃ [Ag (CN)₄]
c. Na₅ [Ag (CN)₆]
d. Na₂ [Ag (CN)₂]
Answer : A

Question. The cation that does not form an amine complex with excess of ammonia is:
a. Cd²⁺
b. Al³⁺
c. Cu²⁺
d. Ag⁺
Answer : B

Question. Ziegler-Natta catalyst is an organometallic compound of which metal:
a. Iron
b. Zirconium
c. Rhodium
d. Titanium
Answer : D

Question. Which of the following is formed when n-butyl lithium reacts with tin (II) chloride:
a. LiBr
b. Et₄ Pb
c. (C₄H₉)₄ Sn
d. (C₂H₅)₄ Pb
Answer : C

Question. Which one is not an organometallic compound?
a. RMgX
b. C₂H₅ONa
c. (CH₃)₄ Sn
d. KC₄H₉
Answer : B

Question. Among the following, which is not the π-bonded organometallic compound:
a. (CH₃)₄ Sn
b. K[PtCl₃ (η₂ – C²H₄)]
c. Fe (η⁵ – C₅H₅)₂
d. Cr (η⁶ – C₆H₆)₂
Answer : A

Question. Wilkinson's catalyst is used in
a. Polymerization
b. Condensation
c. Halogenation
d. Hydrogenation
Answer : D

Question. Which of the following is an organo-metallic compound?
a. Lithium ethoxide
b. Ethyl lithium
c. Lithium acetate
d. Lithium carbide
Answer : 

Question. Which of the following is not an organometallic compound?
a. Ethyl magnesium bromide
b. Tetraethyl lead
c. Sodium ethoxide
d. Trimethyl aluminium
Answer : C

Question. Which of the following does not have a metal carbon bond?
a. K [Pt (C₂ H₄) Cl₃]
b. Ni (CO)₄
c.  Al(OC₂H₅)₃
d. C₂H₅ MgBr
Answer : C

Question. Coordination compounds have great importance in biological systems. In this context which of the following statements is incorrect:
a. Cyanocobalamin is B₁₂ and contains cobalt.
b. Haemoglobin is the red pigment of blood and contains iron.
c. Chlorophylls are green pigments in plants and contains calcium.
d. Carboxypepticase-A is an enzyme and contains zinc.
Answer : C

Question. The π – bonded organo metallic compound which has ethene as one of its component is:
a. Zeise's salt
b. Ferrocene
c. Dibenzene chromium
d. Tetraethyl tin.
Answer : C

Question. Which of the following statements is correct for the complex [Fe(HeO) NO]SO ?
a. The EAN value of Fe in this complex depends on the charge of NO ligand
b. The EAN value of Fe in this complex does not depends on the charge of NO ligand
c. The hybridization of the central atom is d²sp³.
d. It is paramagnetic with μ = 1.73 B.M.
Answer : B

Question. [Fe(NO₂)₃Cl₃] and [Fe (ONO)₃Cl₃] show
(a) Linkage isomerism
(b) Optical isomerism
(c) Geometrical isomerism
(d) None of these
Answer. A

Question. The diamagnetic species is
(a) [Ni(CN)₄]^2-
(b) [NiCl₄]^2-
(c) [CuCl₄]^2-
(d) [CoF₆]^3-
Answer. B

Question. The oxidation state of Cr in [Cr(NH₃)₄Cl₂]⁺ is
(a) +3
(b) +1
(c) +2
(d) 0
Answer. A

Question. The spin only magnetic moment of [Ni( Cl₄)]^2- is
(a) 1.82 BM
(b) 5.46 BM
(c) 2.82BM
(d) 1.41 BM
Answer. C

Question. The type of isomerism shown by the complex [CoCl₂(en)₂] is
(a) Ionization isomerism
(b) Coordination isomerism
(c) Geometrical isomerism
(d) Linkage isomerism
Answer. C

Question. The geometry and magnetic behaviour of the complex [Ni(CO)₄] are
(a) Square planar and paramagnetic
(b) Tetrahedral and diamagnetic
(c) Square planar and diamagnetic
(d) Tetrahedral and paramagnetic
Answer. B

Question. Correct increasing order for the wavelengths of absorption in the visible region in the complexes of Co³⁺ is
(a) [Co(H₂O)₆]³⁺ , [Co (en)₃]³⁺ , [Co(NH₃)₆]³⁺
(b) [Co(H₂O)₆]³⁺, [Co(NH₃)₆]³⁺ , [Co (en)₃]³⁺
(c) [Co(NH₃)₆]³⁺, [Co (en)₃]³⁺, [Co(H₂O)₆]³⁺
(d) [Co (en)₃]³⁺,[Co(NH₃)₆]³⁺, [Co(H₂O)₆]³⁺
Answer. D

Question. Which of the following complexes is used to be as an anticancer agent
(a) Na₂CoCl₄
(b) cis-[PtCl₂(NH₃)₂]
(c) mer-[Co (NH₃)₃Cl₃]
(d) cis-K₂ [PtCl₂Br₂]
Answer. B

Question. The IUPAC name of complex ion ,[Fe(CN)₆]^3- is
(a) Hexacyanidoiron(III)ion
(b) Hexacyanatoferrate (III)ion
(c) Hexacyanidoferrate (III)ion
(d) Tricyanoiron(III)ion
Answer. C

Question. Which of the following complex has minimum magnitude of Δo ?
(a) [Cr (CN)₆]^3-
(b) [Co (NH₃)₆]³⁺
(c) [Co (Cl)₆]^3-
(d) [Cr (H₂O)₆]³⁺
Answer. C

Question. The hybridisation involved in the complex [Ni(CN)₄]^2- is
(a) d²sp²
(b) d²sp³
(c) dsp²
(d) sp³
Answer. C

SHORT ANSWER TYPE QUESTIONS

Question. Write the IUPAC names of the following coordination compounds.
Answer. 
(i) K₃[Fe(C₂O₄)₃]     Potasium trioxalatoferrate(III)
(ii) K₂[PdCl₄]            Potasium tetrachloridopalladate(II)
(iii) K₃[FeF₆]            Potassium hexafluoroferrate (III)
(iv) [Zn(OH)₄] ^-2     Tetrahydroxozincate (II) ion
(v) [Pt(NH₃)₄Cl₂] [PtCl₆]   Tetraamminedichloroplatinum (IV) hexachloroplatinate (IV)

Question. Write the formula for each of the following complex compounds or ions.
Answer.(i)Hexaamminecobalt (III) chloride [Co (NH₃)₆] Cl₃
(ii)Diamminetetrabromoplatinum (VI) bromide [Pt (NH₃)₂ Br₄] Br₂
(iii)Tetraaquacadmium (II) nitrate [Cd (H₂O)₄] (NO₃)₂
(iv)Sodium tetracyanocuprate (I) Na₃[Cu (CN)₄]
(v)Silver hexacyanoferrate (II) Ag4[Fe (CN)₆]

Question. Give reasons
Question. CuSO₄ 5H₂O is blue in colour while CuSO₄ is colourless.
Answer. In CuSO₄ 5H₂O , water acts as ligand and causes crystal field splitting. Hence d-d transition is possible and shows colour.
In anhydrous CuSO₄ crystal field splitting is not possible due to absence of ligand and is colourlesss.

Question. Low spin tetrahedral complexes not formed
Answer. In a tetrahedral complex, the d-orbital is split too small as compared to octahedral complex. For the same metal and same ligand Δt = 4/9Δo.Hence, the orbital energies are not enough to force pairing. As a result, low spin configurations are rarely observed in tetrahedral complexes.

Question. Arrange the following complexes in the increasing order of conductivity of their solution:
[Co(NH₃)₃Cl₃], [Co(NH₃)₄Cl₂]CI, [Co(NH₃)₆]Cl₃, [Cr(NH₃)₅Cl]Cl₂
Answer. Co(NH₃)₃Cl₃] < [Co(NH₃)₄Cl₂]Cl < [Cr(NH₃)₅Cl]Cl₂ < [Co(NH₃)₆]Cl₃
Here, the number of ions increases and conductivity increases.

Question. A coordination compound CrCl₃. 4H₂O precipitates silver chloride when treated with silver nitrate. The molar conductance of its solution corresponds to a total of two ions. Write the structural formula of the compound and name it.
Answer. Silver chloride precipitates when treated with silver nitrate because there is chloride ion outside the complex. There is only one chloride ion outside the complex since only two ions are generated. As a result, the compound’s structural formula and nomenclature are:
[Co(H₂O)₄Cl₂]Cl – Tetraaquadichloridocobalt(III) chloride.

Question. Explain why [Fe(H₂O)₆]³⁺ has a magnetic moment value of 5.92 BM whereas [Fe(CN)₆]^3- has a value of only 1.74 BM.
Answer. [Fe(CN)₆]^{3– i}nvolves d²sp³ hybridisation with one unpaired electron and [Fe(H₂O)₆]³⁺ involves sp³d² hybridisation with five unpaired electrons. This difference is due to the presence of strong ligand CN– and weak ligand H₂O in these complexes.

Question. Arrange the following complex ions in increasing order of crystal field splitting energy (Δo) : [Cr(Cl)₆]^3–, [Cr(CN)₆]^3–, [Cr(NH₃)₆]³⁺.
Answer. The order of increasing Δo value for the complex ions is:
[Cr(Cl)₆]^3– < [Cr(CN)₆]^3– < [Cr(NH₃)₆]³⁺
This is because of the increasing order of the Δo values of the ligands in the spectrochemical series.

Question. Give an example in each case the role of coordination compound in (i) Biological systems (ii) Medicinal chemistry (iii) Heterogeneous catalysis (iv) extraction of metals
Answer. (i) In biological system Chlorophyll & Hemoglobin is a complex of Mg²⁺ & Fe³⁺ respectively.
(ii) cis-platin or cis- [Pt (NH₃)₂Cl₂] is used in the treatment of cancer.
(iii)Wilkinson catalyst [(Ph₃)₃RhCl] is used for hydrogenation of alkenes.
(iv) In extraction of metals like gold silver complex Na [Ag(CN)₂]is formed.

Question. Tetrahedral complexes do not show geometrical isomerism. Why?
Answer. (i)All four ligands in tetrahedral complex are adjacent or equidistant to one another
(ii) The relative positions of donor atoms of ligands attached to the central atom are the same with respect to each other

LONG ANSWER TYPE QUESTIONS

Question. FeSO₄ solution mixed with (NH₄)₂SO₄ solution in 1:1 molar ratio gives the test of Fe²⁺ ion but CuSO₄ solution mixed with aqueous ammonia in 1:4 molar ratio does not give the test of Cu²⁺ ion. Explain why?
Answer. (NH₄)₂SO₄ + FeSO₄ + 6H₂O → FeSO₄ (NH₄)₂SO₄.6H₂O(Mohr’s salt)
CuSO₄ + 4NH₃ +5H₂O → [Cu(NH₃)₄]SO₄.5H₂O (Teraaminecopper(II) sulphate)
Both the compounds fall under the category of addition compounds with only one major difference i.e., the former is an example of a double salt, while the latter is a coordination compound. A double salt is an addition compound that is stable in the solid state but that which breaks up into its constituent ions in the dissolved state. These compounds exhibit individual properties of their constituents. For e.g. FeSO₄.(NH₄)₂SO₄.6H₂O breaks into Fe²⁺, NH₄⁺, and SO₄²⁻ ions. Hence, it gives a positive test for Fe²⁺ ions.
A coordination compound is an addition compound which retains its identity in the solid as
well as in the dissolved state. However, the individual properties of the constituents are lost. [Cu(NH₃)₄]SO₄.5H₂O does not show the test for Cu²⁺.The ions present in the solution of [Cu(NH₃)₄]SO₄.5H₂O are [Cu(NH₃)₄]²⁺ and SO₄ ^2-

Question. What is meant by crystal field splitting? How t_2g and e_g orbitals are formed in an octahedral complex?
Answer. In case of free metal ion all the five d orbitals have the same energy and are called degenerate orbitals. The five degenerate orbitals of metal ion split into different sets of orbitals having different energies in the presence of electrical field of ligands. This is called crystal field splitting.
In an octahedral complex, the ligands are present at the corners of an octahedron. As lobes of dx²- y² and dz² lie along the axes, ie along the ligands the repulsions are more along the axis. The degeneracy of d orbitals is lifted and these split into two set of orbitals t_2g and e_g, slightly different in energy.

CASE BASED QUESTIONS

Read the following paragraph and answer the questions.

Isomerism is a phenomenon in which compounds have the same molecular formula but different physical and chemical properties on account of different structures. The two major types of isomerism are structural and stereo isomerism. The structural isomerism is further divided into four types. Linkage, coordination, ionisation and solvate isomerism while the stereo isomerism is divided into two types: Geometrical and optical isomerism.

Question. Name the type of isomerism exhibited by [Co(NH₃)3NO₂]₃
Answer. Linkage isomerism

Question. The complexes [Co(NH₃)₆] [Cr(CN)₆] and [Cr(NH₃)₆] [Co(CN)6]are the examples of which type of isomerism
Answer. Coordination isomerism

Question. Square planar complexes of MX₂L₂ type with coordination number 4 exhibit geometrical isomerism whereas tetrahedral complexes with similar composition do not .Why?
Answer. Because the relative positions of the ligands attached to the central metal atom are same with respect to each other in tetrahedral complexes.

Question. Name the type of structural isomerism exhibited by the compound [Co(NH₃)₅SO₄Br]
Answer. Ionization isomerism

Question. Write the name of the linkage isomer of [Co(NH₃)₅NO₂Cl₂]
Answer. Pentaamminenitrito-O-cobalt(III)chloride

Read the following paragraph and answer the questions.

In 1823, Werner put forth this theory to describe the structure and formation of complex compounds or coordination compounds. It is because of this theory that he got the Nobel prize and is known as the father of coordination chemistry. According to his theory The central metals of coordination compounds exhibit two types of valencies, primary valency and secondary valency. The primary valencies are ionizable. These are written outside the coordination sphere. These are non-directional and do not give any geometry to complex compound. The secondary valency of metals is either by negative ions or neutral molecules or both. In modern terminology it represents the coordination number of the metal. Secondary valencies are written inside the coordination sphere. These are directional in nature and give definite geometry to the complex. These are non-ionisable.

Question. A coordination compound CrCl₃.4H₂O precipitates silver chloride when treated with silver nitrate. The molar conductance of its solution corresponds to a total of 2 ions. Write the structural formula of the complex.
Answer. [Co(H₂O)₄Cl₂]Cl

Question. The increasing order of conductivity of the following complexes in their solutions [Co(NH₃)₃Cl₃] , [Co(NH₃)₆Cl₃ ,[Co (NH₃)₄Cl₂]Cl
Answer. [Co(NH₃)₃Cl₃], ,[Co (NH₃)₄Cl₂]Cl, [Co(NH₃)₆Cl₃

Question. Write the correct formula for the following coordination compound CrCl₃.6H₂O with 3 chloride ions precipitated as AgCl.
Answer. [Cr(H₂O)₆]Cl₃

Question. How many ions are produced from the complex [Co(NH₃)₅Cl]Cl₂ in solution ?
Answer.3

Question. When a coordination compound PdCl₂.4NH₃ is mixed with AgNO₃, 2 moles of AgCl are precipitated per mole of the compound. Assign secondary valency to the metal.
Answer.4

Read the following paragraph and answer the questions.

Valence bond theory considers the bonding between metal and the ligands as purely covalent. On the other hand the crystal field theory considers the bond to be ionic purely arising from electrostatic interactions between the metal ion and the ligands. In coordination compounds the interaction between the metal ion and the ligands causes the 5 d orbitals to split up. This is called crystal field splitting and the energy difference between the two sets of orbitals is called crystal field splitting energy. CFSE depends upon the nature of the ligand.

Question. Write the electronic configuration of [CoF₆] ^3- on the basis of crystal field theory
Answer. Co³⁺ has ( d⁶) ; t_2g⁴e_g ² configuration

Question. Arrange the following complex ions in the increasing order of crystal field splitting energy [CrCl₆]^3- , [Cr(CN)₆]^3-,[Cr(NH₃)₆]³⁺
Answer. [CrCl₆]^3- , [Cr(NH₃)₆]³⁺,[Cr(CN)₆]^3-

Question. A metal M ⁿ⁺ having d⁴ valence electronic configuration combines with three bi dentate ligands to form a complex compound. On the basis of CFT write the electronic configuration assuming Δo <P
Answer. t_2g³eg ¹

Question. Among the ligands ,NH₃ ,en and CO which ligand is having the highest field strength ?
Answer.CO

Question. What will be the increasing order for the wave lengths of absorption in the visible region of the following :
[Ni (NO₂)₆]^4- , [Ni (NH₃)₆]²⁺,[Ni (H₂O)₆]²⁺
Answer. [Ni (H₂O)₆]²⁺, [Ni (NH₃)₆]²⁺, [Ni (NO₂)₆]₄

Question. Nowadays younger generation girls are interested in wearing ornaments made of white metal platinum
(i) Are you interested in wearing ornaments made of platinum or will you save platinum by not wearing it? Why?
(ii) Name the life saving drug prepared from platinum
(iii) Which disease can be cured by that complex?
Answer:
i. I will not wear but I will save it for medicinal use .
ii. cis platin
iii. to cure cancer

Question. Ram is a poor boy. He never brings lunch to school. Sam is his friend and Sam shares his lunch with Ram.
(i) Which type of value Sam has?
(ii) Seeing this condition which type of chemical bond do you recall?
(iii) Can you give a complex name and formula with this type of bond?
Answer:
i. co-ordinate bond Sam is a kind and helping boy.
ii. coordinate bond
iii. K4[Fe(CN)6 Pottasiumhexacyanoferrate(II).

Question. When cobalt III chloride and ammonia are combined we get yellow, purple, green, violet coloured coordination complexes. Like wise when people make friendship with different type of people their personality changes.
(i) Which type of friends are you?
(ii) Write any one good character of your friend.
(iii) Write any two complex formed by the combination CoCl₃ and NH₃.
Answer:
i. helping in need of my friend.
ii. My friend is affectionate and truthful
iii. [Co Cl₂ (NH₃)₄]Cl and [CoCl (NH₃)₅]Cl₂

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