CBSE Class 12 Chemistry HOTs Coordination Compounds

Question. The correct order of the stoichiometries of AgCl formed when AgNO₃ in excess is treated with the complexes : CoCl₃.6NH₃, CoCl₃.5NH₃, CoCl₃.4NH₃ respectively is
(a) 3AgCl, 1AgCl, 2AgCl
(b) 3AgCl, 2AgCl, 1AgCl
(c) 2AgCl, 3AgCl, 2AgCl
(d) 1AgCl, 3AgCl, 2AgCl
Answer. B

Question. Cobalt(III) chloride forms several octahedral complexes with ammonia. Which of the following will not give test for chloride ions with silver nitrate at 25°C?
(a) CoCl₃ · 5NH₃
(b) CoCl₃ · 6NH₃
(c) CoCl₃ · 3NH₃
(d) CoCl₃  · 4NH₃
Answer. C

Question. An excess of AgNO₃ is added to 100 mL of a 0.01 M solution of dichlorotetraaquachromium(III) chloride.The number of moles of AgCl precipitated would be
(a) 0.003
(b) 0.01
(c) 0.001
(d) 0.002
Answer. C

Question. Which of the following will exhibit maximum ionic conductivity?
(a) K4[Fe(CN)₆]
(b) [Co(NH₃)₆]Cl₃
(c) [Cu(NH₃)₄]Cl₂
(d) [Ni(CO)₄] 
Answer. A

Question. A coordination complex compound of cobalt has the molecular formula 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 this solution with excess of AgNO₃ solution, we get two moles of AgCl precipitate. The ionic formula for this complex would be
(a) [Co(NH₃)₅(NO₂)]Cl₂
(b) [Co(NH₃)₅Cl][Cl(NO₂)]
(c) [Co(NH₃)₄(NO₂)Cl][(NH₃)Cl]
(d) (Co(NH₃)₅][(NO₂)2Cl₂] 
Answer. A

Question. The correct increasing order of trans-effect of the following species is
(a) NH₃ > CN^– > Br^– > C₆H₅^–
(b) CN– > C₆H₅^– > Br– > NH₃
(c) Br– > CN– > NH₃ > C₆H₅^–
(d) CN– > Br– > C₆H₅^–– > NH₃
Answer. B

Question. The sum of coordination number and oxidation number of the metal M in the complex [M(en)₂(C₂O₄)]Cl (where en is ethylenediamine) is
(a) 6
(b) 7
(c) 8
(d) 9
Answer. D

Question. The anion of acetylacetone (acac) forms Co(acac)₃ chelate with Co³⁺. The rings of the chelate are
(a) five membered
(b) four membered
(c) six membered
(d) three membered.
Answer. C

Question. Which of the following statements is true?
(a) Silicon exhibits 4 coordination number in its compound.
(b) Bond energy of F₂ is less than Cl₂.
(c) Mn(III) oxidation state is more stable than Mn(II) in aqueous state.
(d) Elements of 15th gp shows only +3 and +5 oxidation states. 
Answer. B

Question. Coordination number of Ni in [Ni(C₂O₄)₃]^4– is
(a) 3
(b) 6
(c) 4
(d) 2 
Answer. B

Question. The coordination number and oxidation state of Cr in K₃[Cr(C₂O₄)₃] are respectively
(a) 3 and + 3
(b) 3 and 0
(c) 6 and + 3
(d) 4 and + 2
Answer. C

Question. Which of the following ligands is expected to be bidentate?
(a) CH₃NH₂
(b) CH₃C N
(c) Br
(d) C2O₄
Answer. D

Question. The name of complex ion, [Fe(CN)₆]^3– is
(a) hexacyanitoferrate(III) ion
(b) tricyanoferrate(III) ion
(c) hexacyanidoferrate(III) ion
(d) hexacyanoiron(III) ion. 
Answer. C

Question. The correct IUPAC name for [CrF₂(en)₂]Cl is
(a) chlorodifluoridoethylenediaminechromium (III) chloride
(b) difluoridobis(ethylene diamine)chromium (III) chloride
(c) difluorobis-(ethylene diamine)chromium (III) chloride
(d) chlorodifluoridobis(ethylene diamine) chromium (III). 
Answer. B

Question. The hypothetical complex chlorodiaquatriammine cobalt(III) chloride can be represented as
(a) [CoCl(NH₃)₃(H₂O)₂]Cl₂
(b) [Co(NH₃)₃(H₂O)Cl₃]
(c) [Co(NH₂)₃(H₂O)₂Cl]
(d) [Co(NH₃)₃(H₂O)₃]Cl₃
Answer. A

Question. IUPAC name of [Pt(NH₃)₃(Br)(NO₂)Cl]Cl is
(a) triamminebromochloronitroplatinum(IV) chloride
(b) triamminebromonitrochloroplatinum(IV) chloride
(c) triamminechlorobromonitroplatinum(IV) chloride
(d) triamminenitrochlorobromoplatinum(IV) chloride. 
Answer. A

Question. The type of isomerism shown by the complex [CoCl₂(en)₂] is
(a) geometrical isomerism
(b) coordination isomerism
(c) ionization isomerism
(d) linkage isomerism. 
Answer. A

Question. Number of possible isomers for the complex [Co(en)₂Cl₂]Cl will be (en = ethylenediamine)
(a) 1
(b) 3
(c) 4
(d) 2 
Answer. B

Question. The complexes [Co(NH₃)₆][Cr(CN)₆] and [Cr(NH₃)₆][Co(CN)₆] are the examples of which type of isomerism?
(a) Linkage isomerism
(b) Ionization isomerism
(c) Coordination isomerism
(d) Geometrical isomerism 
Answer. C

Question. The complex, [Pt(py)(NH₃)BrCl] will have how many geometrical isomers?
(a) 3
(b) 4
(c) 0
(d) 2 
Answer. A

Question. The existence of two different coloured complexes with the composition of [Co(NH₃)₄Cl₂]⁺ is due to
(a) linkage isomerism
(b) geometrical isomerism
(c) coordination isomerism
(d) ionization isomerism. 
Answer. B

Question. Which one of the following complexes is not expected to exhibit isomerism?
(a) [Ni(NH₃)₄(H₂O)₂]²⁺
(b) [Pt(NH₃)₂Cl₂]
(c) [Ni(NH₃)₂Cl₂]
(d) [Ni(en)₃]²⁺ 
Answer. C

Question. Which of the following does not show optical isomerism?
(a) [Co(NH₃)₃Cl₃]⁰
(b) [Co(en)Cl₂(NH₃)₂]⁺
(c) [Co(en)₃]³⁺
(d) [Co(en)₂Cl₂]⁺(en = ethylenediamine) 
Answer. A

Question. Which of the following will give a pair of enantiomorphs?
(a) [Cr(NH₃)₆][Co(CN)₆]
(b) [Co(en)₂Cl₂]Cl
(c) [Pt(NH₃)₄][PtCl₆]
(d) [Co(NH₃)₄Cl₂]NO₂
(en = NH₂CH₂CH₂NH₂) 
Answer. B

Question. [Co(NH₃)₄(NO₂)₂]Cl exhibits
(a) linkage isomerism, geometrical isomerism and optical isomerism
(b) linkage isomerism, ionization isomerism and optical isomerism
(c) linkage isomerism, ionization isomerism and geometrical isomerism
(d) ionization isomerism, geometrical isomerism and optical isomerism.
Answer. C

Question. Which one of the following is expected to exhibit optical isomerism? (en = ethylenediamine)
(a) cis-[Pt(NH₃)₂Cl₂]
(b) trans-[Pt(NH₃)₂Cl₂]
(c) cis-[Co(en)₂Cl₂]⁺
(d) trans-[Co(en)₂Cl₂]⁺
Answer. C

Question. Which of the following coordination compounds would exhibit optical isomerism?
(a) Pentaamminenitrocobalt(III) iodide
(b) Diamminedichloroplatinum(II)
(c) trans-Dicyanobis(ethylenediamine) chromium(III) chloride
(d) tris-(Ethylenediamine)cobalt(III) bromide
Answer. D

Question. Which of the following will give maximum number of isomers?
(a) [Co(NH₃)₄Cl₂]
(b) [Ni(en)(NH₃)₄]²⁺
(c) [Ni(C₂O₄)(en)₂]^2–
(d) [Cr(SCN)₂(NH₃)₄]⁺
Answer. D

Question. Which complex compound will give four isomers?
(a) [Fe(en)₃]Cl₃
(b) [Co(en)₂Cl₂]Cl
(c) [Fe(PPh₃)₃NH₃ClBr]Cl
(d) [Co(PPh₃)₃Cl]Cl₃ 
Answer. C

Question. The total number of possible isomers for the complex compound [CuII(NH₃)₄][PtIICl₄] are
(a) 5
(b) 6
(c) 3
(d) 4 
Answer. D

Question. The number of geometrical isomers of the complex [Co(NO₂)₃(NH₃)₃] is
(a) 4
(b) 0
(c) 2
(d) 3 
Answer. C

Question. The number of geometrical isomers for [Pt(NH₃)₂Cl₂] is
(a) 3
(b) 4
(c) 1
(d) 2
Answer. D

Question. Which of the following is the correct order of increasing field strength of ligands to form coordination compounds?
(a) SCN^– < F– < C₂O₄^2– < CN^–
(b) SCN^– < F^– < CN^– < C₂O₄^2–
(c) F^– < SCN^– < C₂O₄^2– < CN^–
(d) CN^– < C₂O₄^2– < SCN^– < F^– 
Answer. A

Question. Aluminium chloride in acidified aqueous solution forms a complex ‘A’, in which hybridisation state of Al is ‘B’. What are ‘A’ and ‘B’, respectively ?
(a) [Al(H₂O)₆]³⁺, sp³d²
(b) [Al(H₂O)₄]³⁺, sp³
(c) [Al(H₂O)₄]³⁺, dsp²
(d) [Al(H₂O)₆]³⁺, d²sp³
Answer. A

Question. The crystal field stabilisation energy (CFSE) for [CoCl₆]^4– is 18000 cm^–1. The CFSE for [CoCl₄]^2– will be
(a) 6000 cm^–1
(b) 16000 cm^–1
(c) 18000 cm^–1
(d) 8000 cm^–1
Answer. D

1 Mark Questions

1. Write the IUPAC name of the complex Na₃[Cr(OH)₂F₄].

2. Write the IUPAC name of [CO(en)₂Cl(ONO)]⁺

3. Which of these cannot act as ligand and why: NH₃, H₂O, CO, CH₄. Give reason?

4. NH3 is strong ligand NH4⁺ ion is not, why?

5. Which of the two is more stable K₄[Fe(CN)₆] or K₃[Fe(CN)₆].

2 / 3 Mark Questions

1. A coordination compound has a formula (CoCl₃. 4NH₃). It does not liberate NH3 but precipitates chloride ion as AgCl. Give the IUPAC name of the complex and write its structural formula.

2. How is stability of co-ordination compounds determined in aqueous solution? Select a complex formation reaction and write an expression for the stability constant of the complex. Mention the factors affecting stability of complexes.

3. Why do tetrahedral complex not show geometrical isomerism?

4. Write the correct formula for the following co-ordination compounds.

CrCl₃ . 6H₂O (Violet, with 3 Chloride ions/ Unit formula)

CrCl₃ . 6H₂O (Light green colour with 2 Chloride ions/ unit formula)

CrCl₃ . 6H₂O (Dark green colour, with 1 Chloride ion/ unit formula)

5. Aqueous copper sulphate solution (blue in colour) gives:

a. a green precipitate with aqueous potassium flouride

b. a bright green solution with aqueous potassium chloride. Explain these experimental results.

6. Identify complexes with different geometries depending upon the type of hybridization.

(a) [Co (NH₃)₆]³⁺ (b) [CoF6]^3-

7. One mole of complex compound Co(NH₃)5Cl₃ gives 3 moles of ions on dissolution in water. One mole of same complex reacts with 2 moles of AgCl(s). What is the structure of the complex and write its formula.

8. When an aquous solution of Nickel (II) chloride is mixed with ethane-1,2 diamine(en) in the molar ratios en : Ni=1:1, 2:1 and 3:1, the green coloured solution finally turns violet. Explain the chemical reactions based on the data provided.