CBSE Class 12 Chemistry Coordination Compounds Worksheet Set 02

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SHORT ANSWER TYPE QUESTIONS

Question.Give the electronic configuration of the following complexes on the basis of Crystal Field Splitting theory.
[CoF6]3-, [Fe(CN)6]4- and [Cu(NH3)6]2+.
Answer. [CoF6]3- = Co3+ = (d)6 = t2g4eg2
[Fe(CN)6]4- = Fe2+ = (d)6 = t2g6eg0
[Cu(NH3)6]2+ = Cu2+ = (d)9 = t2g6eg3

Question. [Ni(CN)4]2- is colourless where as [Ni(H2O)6]2+ is green. Why?
Answer. In [Ni(CN)4]2-, Ni is in +2 oxidation state with electronic configuration 3d8. In the presence of strong CN- ligand the two unpaired electron in 3d orbital pair up. As there is no unpaired electron, it is colourless.
In [Ni(H2O)6]2+ Ni is +2 oxidation state and electronic configuration 3d8. The two unpaired electrons do not pair up in the presence of weak ligand H2O. The d-d transition absorbs red light and complementary green light is emitted.

Question. Give the formula of each of the following coordination entities:
(i) Co 3+ ion bound to one Cl- , one NH3 molecule and two ethylene diamine molecules.
(ii) Ni 2+ ion is bound to two water molecules and two oxalate ions.
Answer. (i) [Co (NH3)Cl (en)2]2+ (ii)Ni(H2O)2(ox)2] 2-

Question. A metal complex having composition Cr(NH3)4Cl2Br has been isolated in two forms A & B. The form A reacts with AgNO3 solution to give a white precipitate soluble in aq. Ammonia whereas B gives a pale yellow precipitate soluble in concentrated ammonia. Write the formulae of A&B.
Answer. A is [Cr(NH3)4ClBr]Cl B is [Cr(NH3)4Cl2]Br


CASE BASED QUESTIONS

I. Read the given passage and answer the questions that follow.

Complex compounds play an important role in our daily life. Werner’s theory of complex compounds says every metal atom or ion has primary valency (oxidation state) which is satisfied by –vely charged ions, ionisable where secondary valency (coordination number) is non-ionisable, satisfied by ligands (+ve, –ve, neutral) but having lone pair. Primary valency is non-directional, secondary valency is directional. Complex compounds are name according to IUPAC system. Valence bond theory helps in determining shapes of complexes based on hybridisation, magnetic properties, outer or inner orbital complex. Complex show ionisation, linkage, solvate and coordination isomerism also called structural isomerism. Some of them also show stereoisomerism i.e. geometrical and optical isomerism. Ambidentate ligand are essential to show linkage isomerism. Polydentate ligands form more stable complexes then unidentate ligands. There are called chelating agents. EDTA is used to treat lead poisoning, cis-platin as anticancer agents. Vitamin B12 is complex of cobalt. Haemoglobin, oxygen carrier is complex of Fe2+ and chlorophyll essential for photosynthesis is complex of Mg2+.

Question. What is the oxidation state of Ni in [Ni(CO)4]?
Answer. Zero

Question. One mole of CrCl3 . 6H2O reacts with excess of AgNO3 to yield 2 mole of AgCl. Write formula of complex. Write IUPAC name also.
Answer. [Cr(H2O)5Cl]Cl2 . H2O, pentaaquachloridochromium (III) chloride.

Question. Out Cis – [Pt(en)2 Cl2] 2+ and trans [Pt(en)2Cl2] 2+ which one shows optical isomerism?
Answer. Cis – [Pt(en)2 Cl2] 2+ shows optical isomerism.

Question. Name the hexadentate ligand used for treatment of lead poisoning.
Answer. EDTA4– (ethylenediamine tetraacetate)

Question. What is hybridisation of [CoF6] 3–? [Co = 27] Give its shape and magnetic properties.
Answer. Sp3d2 , octahedral, paramagnetic.

Question. What type of isomerism is shown by [Cr(H2O)6] Cl3 and [Cr(H2O)5 Cl] Cl2 .H2O?
Answer. Solvate isomerism.

 

1. Give IUPAC name of the following co-ordination compounds:
(i) [Cr(NH3)3CL3]
(ii) K3[Fe(CN)6]
(iii) [CoBr2(en)6]+

2. How would you account for the following?
(i) Transition metals exhibit variable oxidation states.
(ii) Zr(z=40) and Hf(z=72) have almost identical radii.
(iii) Transition metals and their compounds act as catalyst.

3. Complete the following equations
(i) Cr2O7 + 6Fe2+ + 14 H+ →
(ii) 2CrO42- 2H+ →
(iii) 2MnO4- + 5C2O42- +16 H+ →

4. (a) Which metal in the first transition series exhibits +1 oxidation state frequently and Why?
(b) Which of the following cations are coloured in aqueous solution and why? Sc3+, V3+ , Ti4+ , Mn2+ 

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

Question. Correct increasing order for the wavelengths of absorption in the visible region for 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. Pick out the correct statement with respect to [Mn(CN)6]3–.
(a) It is sp3d2 hybridised and tetrahedral.
(b) It is d2sp3 hybridised and octahedral.
(c) It is dsp2 hybridised and square planar.
(d) It is sp3d2 hybridised and octahedral.
Answer. B

Question. Jahn–Teller effect is not observed in high spin complexes of
(a) d7
(b) d8
(c) d4
(d) d9 
Answer. B

Question. The hybridization involved in complex [Ni(CN)4]2– is (At. No. Ni = 28)
(a) sp3
(b) d2sp2
(c) d2sp3
(d) dsp2
Answer. D

Question. Among the following complexes the one which shows zero crystal field stabilization energy (CFSE) is
(a) [Mn(H2O)6]3+
(b) [Fe(H2O)6]3+
(c) [Co(H2O)6]2+
(d) [Co(H2O)6]3+ 
Answer. B

Question. A magnetic moment at 1.73 BM will be shown by one among of the following
(a) TiCl4
(b) [CoCl6]4–
(c) [Cu(NH3)4]2+
(d) [Ni(CN)4]2–
Answer. C

Question. Crystal field splitting energy for high spin d4 octahedral complex is
(a) – 1.2 Δo
(b) – 0.6 Δo
(c) – 0.8 Δo
(d) – 1.6 Δo
Answer. B

Question. Which among the following is a paramagnetic complex?
(a) [Co(NH3)6]3+
(b) [Pt(en)Cl2]
(c) [CoBr4]2–
(d) Mo(CO)6
(At. No. Mo = 42, Pt = 78)
Answer. C

Question. Which is diamagnetic?
(a) [CoF6]3–
(b) [Ni(CN)4]2–
(c) [NiCl4]2–
(d) [Fe(CN)6]3–
Answer. B

Question. Which one of the following is an outer orbital complex and exhibits paramagnetic behaviour?
(a) [Ni(NH3)6]2+
(b) [Zn(NH3)6]2+
(c) [Cr(NH3)6]3+
(d) [Co(NH3)6]3+
Answer. A

Question. Of the following complex ions, which is diamagnetic in nature?
(a) [NiCl4]2–
(b) [Ni(CN)4]2–
(c) [CuCl4]2–
(d) [CoF6]3–
Answer. B

Question. The d-electron configurations of Cr2+, Mn2+, Fe2+ and Co2+ are d4, d5, d6 and d7 respectively.Which one of the following will exhibit minimum paramagnetic behaviour?
(a) [Mn(H2O)6]2+
(b) [Fe(H2O)6]2+
(c) [Co(H2O)6]2+
(d) [Cr(H2O)6]2+
(At. nos. Cr = 24, Mn = 25, Fe = 26, Co = 27) 
Answer. C

Question. Which of the following complex compounds will exhibit highest paramagnetic behaviour?
(a) [Ti(NH3)6]3+
(b) [Cr(NH3)6]3+
(c) [Co(NH3)6]3+
(d) [Zn(NH3)6]3+
(At. No. Ti = 22, Cr = 24, Co = 27, Zn = 30) 
Answer. B

Question. Which of the following complex ions is not expected to absorb visible light?
(a) [Ni(CN)4]2–
(b) [Cr(NH3)6]3+
(c) [Fe(H2O)6]2+
(d) [Ni(H2O)6]2+ 
Answer. A

Question. Crystal field stabilization energy for high spin d4 octahedral complex is
(a) – 1.8 Δo
(b) – 1.6 Δo + P
(c) – 1.2 Δo
(d) – 0.6 Δo
Answer. D

Question. Out of TiF62–, CoF63–, Cu2Cl2 and NiCl42– (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28) the colourless species are
(a) Cu2Cl2 and NiCl42–
(b) TiF62– and Cu2Cl2
(c) CoF63– and NiCl42–
(d) TiF62– and CoF6 3–.
Answer. B

Question. Which of the following complex ions is expected to absorb visible light?
(a) [Ti(en)2(NH3)2]4+
(b) [Cr(NH3)6]3+
(c) [Zn(NH3)6]2+
(d) [Sc(H2O)3(NH3)3]3+
[At. nos. Zn = 30, Sc = 21, Ti = 22, Cr = 24] 
Answer. B

Question. Which of the following complexes exhibits the highest paramagnetic behaviour?
(a) [Co(ox)2(OH)2]–
(b) [Ti(NH3)6]3+
(c) [V(gly)2(OH)2(NH3)2]+
(d) [Fe(en)(bpy)(NH3)2]2+
where gly = glycine, en = ethylenediamine and bpy = bipyridyl moities. (At. nos. Ti = 22, V = 23,Fe = 26, Co = 27)
Answer. A

Question. In which of the following coordination entities the magnitude of Do (CFSE in octahedral field) will be maximum?
(a) [Co(CN)6]3–
(b) [Co(C2O4)3]3–
(c) [Co(H2O)6]3+
(d) [Co(NH3)6]3+
(At. No. Co = 27) 
Answer. A

Question. The d electron configurations of Cr2+, Mn2+, Fe2+ and Ni2+ are 3d4, 3d5, 3d6 and 3d8 respectively.Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour?
(a) [Fe(H2O)6]2+
(b) [Ni(H2O)6]2+
(c) [CrH2O)6]2+
(d) [Mn(H2O)6]2+.
(At. No. Cr = 24, Mn = 25, Fe = 26, Ni = 28)
Answer. B

Question. Which one of the following is an inner orbital complex as well as diamagnetic in behaviour?
(a) [Zn(NH3)6]2+
(b) [Cr(NH3)6]3+
(c) [Co(NH3)6]3+
(d) [Ni(NH3)6]2+
(Atomic number : Zn = 30, Cr = 24, Co = 27, Ni = 28) 
Answer. C

Question. Among [Ni(CO)4], [Ni(CN)4]2–, [NiCl4]2– species, the hybridisation states at the Ni atom are, respectively
(a) sp3, dsp2, dsp2
(b) sp3, dsp2, sp3
(c) sp3, sp3, dsp2
(d) dsp2, sp3, sp3.
[Atomic number of Ni = 28]
Answer. B

Question. CN– is a strong field ligand. This is due to the fact that
(a) it carries negative charge
(b) it is a pseudohalide
(c) it can accept electrons from metal species
(d) it forms high spin complexes with metal species. 
Answer. B

Question. Considering H2O as a weak field ligand, the number of unpaired electrons in [Mn(H2O)6]2+ will be (atomic number of Mn = 25)
(a) three
(b) five
(c) two
(d) four. 
Answer. B

Question. In an octahedral structure, the pair of d orbitals involved in d2sp3 hybridisation is
(a) d x2−y2 dz2 ,
(b) dxz dx2− y2
(c) dz2 , d xz
(d) dxy , dyz. 
Answer. A

Question. The number of unpaired electrons in the complex ion [CoF6]3– is
(a) 2
(b) 3
(c) 4
(d) zero
(Atomic no. : Co = 27)
Answer. C

Question. Atomic number of Cr and Fe are respectively 24 and 26, which of the following is paramagnetic with the spin of electron?
(a) [Cr(CO)6]
(b) [Fe(CO)5]
(c) [Fe(CN)6]4–
(d) [Cr(NH3)6]3+
Answer. D

Question. Which statement is incorrect?
(a) Ni(CO)4 - tetrahedral, paramagnetic
(b) [Ni(CN)4]2– - square planar, diamagnetic
(c) Ni(CO)4 - tetrahedral, diamagnetic
(d) [NiCl4]2– - tetrahedral, paramagnetic 
Answer. A

Question. Iron carbonyl, Fe(CO)5 is
(a) tetranuclear
(b) mononuclear
(c) trinuclear
(d) dinuclear.
Answer. B

Question. An example of a sigma bonded organometallic compound is
(a) Grignard’s reagent
(b) ferrocene
(c) cobaltocene
(d) ruthenocene.
Answer. A

Question. Which of the following has longest C—O bond length? (Free C—O bond length in CO is 1.128 Å.)
(a) [Fe(CO)4]2–
(b) [Mn(CO)6]+
(c) Ni(CO)4
(d) [Co(CO)4]–
Answer. A

Question. Which of the following carbonyls will have the strongest C – O bond?
(a) Mn(CO)6+
(b) Cr(CO)6
(c) V(CO)6–
(d) Fe(CO)5 
Answer. A

Question. Which of the following does not have a metal - carbon bond?
(a) Al(OC2H5)3
(b) C2H5MgBr
(c) K[Pt(C2H4)Cl3]
(d) Ni(CO)4 
Answer. A

Question. Among the following which is not the p-bonded organometallic compound?
(a) K [PtCl3(h2 – C2H4)]
(b) Fe (h5 – C5H5)2
(c) Cr(h6 – C6H6)2
(d) (CH3)4Sn 
Answer. D

Question. Which of the following organometallic compounds is s and p-bonded?
(a) [Fe(h5 – C5H5)2]
(b) K[PtCl3(h2 – C2H4)]
(c) [Co(CO)5NH3]2+
(d) Fe(CH3)3 
Answer. C

Question. Shape of Fe(CO)5 is
(a) octahedral
(b) square planar
(c) trigonal bipyramidal
(d) square pyramidal.
Answer. C

Question. In metal carbonyl having general formula M(CO)x where M = metal, x = 4 and the metal is bonded to
(a) carbon and oxygen
(b) C O
(c) oxygen
(d) carbon.
Answer. D

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

Question. Copper sulphate dissolves in excess of KCN to give
(a) Cu(CN)2
(b) CuCN
(c) [Cu(CN)4]3–
(d) [Cu(CN)4]2–
Answer. C

Question. In the silver plating of copper, K[Ag(CN)2] is used instead of AgNO3. The reason is
(a) a thin layer of Ag is formed on Cu
(b) more voltage is required
(c) Ag+ ions are completely removed from solution
(d) less availability of Ag+ ions, as Cu cannot displace Ag from [Ag(CN)2]– ion. 
Answer. D

Question. CuSO4 when reacts with KCN forms CuCN, which is insoluble in water. It is soluble in excess of KCN, due to formation of the following complex
(a) K2[Cu(CN)4]
(b) K3[Cu(CN)4]
(c) CuCN2
(d) Cu[KCu(CN)4] 
Answer. B

Question. Hypo is used in photography to
(a) reduce AgBr grains to metallic silver
(b) convert metallic silver to silver salt
(c) remove undecomposed silver bromide as a soluble complex
(d) remove reduced silver.
Answer. C

 

Q1. Give IUPAC names of the following:-

(a) Na2[CrF4O]

(b) K[Pt(NH3)Cl3]

(c) Na2[SiF6]

(d) [CoCl(en)2(ONO)]+

(e) [Co(NH3)3(CO3)]Cl

(f) [Pt(NH3)2(py)2] [PtCl4]

(g) [Cr(PPH3) (CO)5]

(h) [Mn3(CO)12]

(i) [CO(NH3)6]ClSO4

(j) K3[AL(C2O4)3]

(k) Hg[Co(SCN)4]

(l) K2[Zn(OH)4]

(m) [CO(en)3] [Cr(CN)6]

(n) Cs [Fecl4]

Q2. Give one chemical test to distinguish between [CO (NH3)5Br] SO4 and [CO (NH3)5SO4] Br.

Q3. A coordination compound has formula Cocl3 4NH3. It does not liberate ammonia but precipitates chloride ions as silver chloride. Give the IUPAC name of complex E-its structural formula.

Q4. The molar conductivity of CaCl3.4NH3.2H2O is found to be same as that of 3:1 electrolyte. What is the structural formula of the complex?

Q5. Give reasons for the following:-

(a) [Fe(CN)6]3 is weakly paramagnetic while [Fe(CN)6]4- is diamagnetic. (VB).

(b) [Ni(CO)4 is tetrahedral while [Ni (CN)4] is square planar. (VB).

(c) [Co(CN)6]3- is low spin complex while [CoF6]3 is a high spin complex (VB)

(d) [Mn(H2O)6]2+ has five unpaired electrons while [Mn(CN)6]4- has only one unpaired. (CFST).

(e) [Ti(H2O)6]3+ is coloured while is [Sc(H2O)6]3+ colorless.

Q6. A, B and C are three complexes of chromium with empirical formula H12O6Cl13Cr. All the three complexes have Cl and H2O molecules as the ligands. Complex A does not react with conc. H2SO4. Complex B and C lose 6.75% and 13.5% of their original weight respectively on heating with Concn H2SO4. Identify A, B and C.
Hint: - Calculate molar mass E-wt of water lost, Correlate it to no. of H2O Molecules lost.

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