Coordination Compounds Class 12 Chemistry Important Questions

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Important Questions of Coordination Compounds Class 12

Very Short Answer Questions

Question. Draw one of the geometrical isomers of the complex [Pt(en)₂Cl₂]²⁺which is optically active.
Answer. cis-isomer of the complex [Pt(en)₂Cl₂]²⁺ is optically active

Question. When a co-ordination compound CrCl₃⋅6H₂O is mixed with AgNO₃, 2 moles of AgCl are precipitated per mole of the compound. Write IUPAC name of the complex.
Answer. IUPAC name of the complex
[CrCl(H₂O)₅]Cl₂ ·H₂O is :
pentaaquachloridochromium (III) chloride.

Question. Give an example of linkage isomerism.
Answer. [Co(NH₃)₅(NO₂)]Cl₂ and [Co(NH₃)₅(ONO)]Cl₂

Question. Name the following coordination compound :
K₃[CrF₆]
Answer. Potassium hexafluoridochromate (III).

Question. Draw the geometrical isomers of complex [Pt(NH₃)₂Cl₂].
Answer. 

Question. What is a ligand? Give an example of a bidentate ligand.
Answer. The ions or molecules bonded to the central atom in the coordination entity are called ligands. Ethylene diammine is a bidentate ligand.

Question. Write the IUPAC name of
[Cr(NH₃)₆ [Co(CN)₆].
Answer. Hexaamminechromium (III) hexacyanocobaltate (III).

Question. Out of NH³ and CO, which ligand forms a more stable complex with a transition metal and why?
Answer. In CO both lone pair of electrons and vacant p* orbitals are present. Hence, it acts as electron pair σ donor as well as p acceptor by back bonding. Hence, M—CO bond is stronger.

NH₃ is electron pair donor only. Accumulation of negative charge on the metal ion takes place, hence M—NH₃ bond is weaker. M ← NH₃

Question. Give an example of coordination isomerism.
Answer. [Co(NH₃)₆][Cr(CN)₆] and [Cr (NH₃)₆] [Co(CN)₆]

Question. Explain the following term giving a suitable example :
Crystal field splitting in an octahedral field.
Answer. The splitting of the degenerate d-orbitals into three orbitals of lower energy, t_2g set and two orbitals of higher energy e_g set due to the interaction of ligand in an octahedral crystal field is known as crystal field splitting in an octahedral field.

Question. Using the IUPAC norms, write the systematic name of the following :
[Co(NH₃)₆] [Cr(CN)₆]
Answer. Hexaamminecobalt (III) hexacyanochromate (III)

Question. Draw one of the geometrical isomers of the complex [Pt(en)₂Cl₂]²⁺ which is optically inactive.
Answer. Trans-isomer is optically inactive due to the presence of plane of symmetry.

Question. Why is CO a stronger ligand than Cl^–?
Answer. Because CO has vacant molecular orbitals with which it can form p-bond with metal through back donation.

Question. Give an example of ionization isomerism.
Answer. [Co(NH₃)₅SO₄]Br and [Co(NH₃)₅ Br] SO₄

Question. Write the IUPAC name of the complex [Cr(NH₃)₄Cl₂]Cl.
Answer. IUPAC name of the complex [Cr(NH₃)4Cl₂]Cl is tetraamminedichloridochromium (III) chloride.

Question. Give IUPAC name of ionisation isomer of [Ni(NH₃)₃NO₃]Cl.
Answer. Ionisation isomer of [(Ni(NH₃)₃NO₃]Cl is [Ni(NH₃)₃Cl]NO₃. The IUPAC name of this complex is triamminechloridonickel (II) nitrate.

Question. Write the IUPAC name of
[PtCl(NH₂CH₃)(NH₃)₂]Cl.
Answer. Diamminechlorido (methylamine) platinum (II) chloride.

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

Question. Give two examples of coordination compounds used in industries.
Answer. (i) EDTA is used for water sofiening and in purification of metals.
(ii) Wilkinson’s catalyst is used as catalyst for hydrogenation.

Question. Write down the formula of :
Tetraamineaquachloridocobalt (III) chloride.
Answer. [Co(NH₃)₄(H₂O)(Cl)]Cl₂

Question. Give names of two complexes which are used in medicines
Answer. cis-Platin is used in the treatment of cancer.
EDTA is used in lead poisoning.

Question. Write the IUPAC name of [Pt(NH₃)₄Cl₂]Cl₂.
Answer. Tetraamminedichloridoplatinum (IV) chloride

Short Answer Questions

Question. Name the following coordination compounds according to IUPAC system of nomenclature :
(i) [Co(NH₃)₄(H₂O)Cl]Cl₂
(ii) [CrCl₂(en)₂]Cl, (en = ethane – 1,2-diamine)
Answer. (i) Hexaamminecobalt (III) chloride
(ii) Tetrachloridonickelate (II) ion
(iii) Potassiumhexacyanoferrate (III)

Question. Name the following coordination compounds and draw their structures.
(i) [CoCl₂(en)₂]Cl
(ii) [Pt(NH₃)₂Cl(NO₂)]
(At. No. Co = 27, Pt = 78)
Answer. (i) Dichloridobis (ethane-1, 2-diamine)cobalt (III) chloride.

Question. (i) Write down the IUPAC name of the following complex. [Cr (en)₃]Cl₃
(ii) Write the formula for the following complex. Potassium trioxalato chromate (III)
Answer. Tris (ethylenediammine) chromium (III) chloride
(ii) K₃[Cr(ox)₃]

Question. Write the hybridization and shape of the following complexes :
(i) [CoF₆]^3– (ii) [Ni(CN)₄]^2–
(Atomic number : Co = 27, Ni = 28)
Answer. (i) Oxidation state of Co ion in [CoF₆]^3– is +3.

Question. Write the state of hybridization, shape and IUPAC name of the complex [Co(NH₃)₆]³⁺.
(Atomic no. of Co = 27)
Answer. Oxidation of cobalt in [Co(NH₃)₆]³⁺ is +3.

Question. Draw the structure of isomers, if any and write the name of the following complexes :
(i) [Cr(NH₃)₄Cl₂]⁺
(ii) [Co(en)₃]³⁺
Answer. (i) Geometrical isomers of [Cr(NH3)4Cl2]⁺ –Tetraamminedichloridochromium (III) ion

(ii) Optical isomers of [Co(en)₃]³⁺ – Tris(ethane-1,2-diamine)cobalt (III) ion.

Question. Write the name and draw the structures of each of the following complex compounds :
(i) [Co(NH₃)₄(H₂O)₂]Cl₃
(ii) [Pt(NH₃)₄][NiCl₄]
Answer. (i) Tetraamminediaquacobalt (III) chloride.

Question. For the complex [Fe(CN)₆]^3–, write the hybridization type, magnetic character and spin nature of the complex. (At. number : Fe = 26).
Answer. Fe atom (Z = 26)

The complex ion has inner orbital octahedral geometry (low spin) and is paramagnetic due to the presence of one unpaired electron.

Question. Write the IUPAC name and indicate the shape of the complex ion [Co(en)₂Cl(ONO)]⁺.
[At. no. Co = 27]
Answer. IUPAC name : Chloridobis(ethylenediamine) nitrito-O-cobalt(III) ion. Shape is octahedral.

Question. Draw the structures of :
(i) Ni(CO)₄ (ii) Fe(CO)₅
Answer. 

Question. For the complex [Fe(H₂O)₆]³⁺, write the hybridization magnetic character and spin of the complex. (At number Fe = 26)
Answer. [Fe(H₂O)₆]³⁺:
Fe atom (Z = 26)

The complex ion has outer orbital octahedral geometry (high spin) and is paramagnetic due to the presence of five unpaired electrons.

Question. Write the IUPAC name of the following :
(i) [Co(NH₃)₆]Cl₃ (ii) [NiCl₄]^2–
(iii) K₃[Fe(CN)₆]
Answer. (i) Tetraammineaquachloridocobalt(III) chloride
(ii) Dichloridobis(ethane-1,2-diamine)cobalt(III) chloride

Long Answer Questions

Question. Write the state of hybridization, the shape and the magnetic behaviour of the following complex entities :
(i) [Cr(NH₃)₄Cl₂]Cl (ii) [Co(en)₃]Cl₃
(iii) K₂[Ni(CN)₄]
Answer. 

Question. Name the following coordination entities and draw the structures of their stereoisomers :
(i) [Co(en)₂Cl₂]⁺ (en = ethane-1,2-diamine)
(ii) [Cr(C₂O₄)₃]^3–
(iii) [Co(NH₃)₃Cl₃]
(Atomic numbers Cr = 24, Co = 27)
Answer. (i) [CoCl₂(en)₂]⁺ : Dichloridobis(ethane-1,2-diamine) cobalt(III) ion
It will exist in two geometrical isomeric forms :

(ii) [Cr(C₂O₄)₃]^3– : Trioxalatochromium(III) ion
It will show optical isomerism.

(iii) [Co(NH₃)₃Cl₃] : Triamminetrichloridocobalt (III)
It will exist in two geometrical isomeric forms:

Question. Write the name, the state of hybridization, the shape and the magnetic behaviour of the following complexes :
[CoCl₄]^2–, [Ni(CN)₄]^2–, [Cr(H₂O)₂(C₂O₄)₂]^–
(At. no. : Co = 27, Ni = 28, Cr = 24)
Answer. [CoCl₄]^2– Tetrachloridocobaltate(II) ion
[Ni(CN)₄]^2– Tetracyanonickelate(II) ion
[Cr(H₂O)₂(C₂O₄)₂]^– Diaquadioxalatochromate(III) ion

Question. Write the IUPAC name and draw the structure of each of the following complex entities :

(iii) [PtCl₃(C₂H₄)]
(At. nos. Cr = 25, Co = 27, Pt = 78)
Answer. (i) Trioxalatocobaltate (III)
(ii) Hexacarbonylchromium (0)
(iii) Trichloroetheneplatinum (III)

Question. For the complex [NiCl₄]^2–, write
(i) the IUPAC name
(ii) the hybridization type
(iii) the shape of the complex.
(Atomic no. of Ni = 28)
Answer. (i) Tetrachloridonickelate(II) ion Ni atom (Z = 28)

The complex ion has tetrahedral geometry and is paramagnetic due to the presence of unpaired electrons

Question. Write the name, the structure and the magnetic behaviour of each one of the following complexes :
(i) [Pt(NH₃)Cl(NO₂)] (ii) [Co(NH₃)₄Cl₂]Cl
(iii) Ni(CO)₄
(At. nos. Co = 27, Ni = 28, Pt = 78)
Answer. (i) [Pt(NH₃)₂Cl(NO₂)] :
Diamminechloridonitrito-N-platinum(II)
It is square planar and diamagnetic.
(ii) [Co(NH₃)₄Cl₂]Cl : Tetraamminedichloridocobalt
(III) chloride It is octahedral and diamagnetic.
(iii) Ni(CO)₄ : Tetracarbonylnickel(0)
It is tetrahedral and diamagnetic