Question

Class 12 Chemistry  MCQ Questions of Coordination Compounds with Answers?

Answer 1

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1. K₂[Fe(CN)₆] is a/an

(a) double salt
(b) complex salt
(c) acid
(d) base

2. According to Werner’s theory of coordination compounds

(a) Primary valency is ion isable
(b) Secondary valency is ionisable
(c) Primary and secondary valencies are lonisable
(d) Neither primary nor secondary valency is ionisable

3. The ligand N(CH₂CH₂NH₂) is

(a) bidentate
(b) tridentate
(c) tetradentate
(d) pentadentate

4. Which of the following ligands form a chelate?

(a) Acetate
(b) Oxalate
(c) Cyanide
(d) Ammonia

5. Which of the following is not a neutral ligand?

(a) H₂O
(b) NH₃
(c) ONO
(d) CO₂

6. Which of the following ligands will not show chelation?

(a) EDTA
(b) DMG
(c) Ethene-1, 2-diamine
(d) SCN^–

7. Which of the following complex species is not expected to exhibit optical isomerism?

(a) [Co(en) (NH₃)₂Cl₂]⁺
(b) [Co(en)₃]³⁺
(c)[Co(en)₂Cl₂]
(d) [Co(NH₃)₃Cl₃]

8. For the square planar complex |M_abcd| where M is the central atom and a, b. c, d are monodentate ligands, the number of possible geometrical isomers are

(a) 1
(b) 2
(c) 3
(d) 4

9. The hybridisation involved in [Co(C₂O₄)₃]^3- is

(a) sp³d²
(b) sp³d³
(c) dsp³
(d) d²sp³

10. The number of unpaired electrons in Ni(CO)₄ is

(a) 0
(b) 1
(c) 3
(d) 5

11. Mercuric chloride is soluble in KI solution due to :

(a) the formation of complex ion
(b) common iodide ion
(c) none of the above
(d) both (a) and (b)

12. The reagent commonly used to determine hardness of water titrimetrically is

(a) oxalic acid
(b) disodium salt of EDTA
(c) sodium citrate
(d) sodium thiosulphate

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

(a) cis-platin
(b) Ferrocene
(c) Zeise's salt
(d) Grignard reagent

14. According to the postulates of Werner for coordination compounds

(a) primary valency is ionizable
(b) secondary valency is ionizable
(c) primary and secondary valencies are non-ionizable
(d) only primary valency is non-ionizable

15. Which one is the most likely structure of CrCl₃. 6H2O if 1/3 of total chlorine of the compound is precipitated by adding AgNO₃

(a) CrCl₃. 6H₂O
(b) [Cr(H₂O)₃ Cl₃]. (H₂O)₃
(c) [CrCl₂(H₂O)₄] Cl . 2H₂O
(d) [CrCl (H₂O)₅] C_l2 .H₂O

16. The coordination number of a central metal atom in a complex is determined by

(a) the number of ligands around a metal ion bonded by sigma and pi-bonds both
(b) the number of ligands around a metal ion bonded by pi-bonds
(c) the number of ligands around a metal ion bonded by sigma bonds
(d) the number of only anionic ligands bonded to the metal ion

17. [EDTA]^4- is a :

(a) monodentate ligand
(b) bidentate ligand
(c) quadridentate ligand
(d) hexadentate ligand

18. Co-ordination number of Ni in [Ni(C₂O₄)₃]^4– is

(a) 3
(b) 6
(c) 4
(d) 5

19. According to Lewis, the ligands are

(a) acidic in nature
(b) basic in nature
(c) some are acidic and others are basic
(d) neither acidic nor basic

20. An example of ambidentate ligand is

(a) Ammine
(b) Aquo
(c) Chloro
(d) Thiocyanato

21. NH₂ -NH₂ serves as

(a) Monodentate ligand
(b) Chelating ligand
(c) Bridging ligand
(d) Both (a) and (c)

22. Which of the following species is not expected to be a ligand?

(a) NO
(b) NH₄
(c) NH₂CH₂CH₂NH₂
(d) Both (a) and (b)

23. The complex ions [Co(NH₃)₅(NO₂)]²⁺ and [Co(NH₃)₅ (ONO)]²⁺ are called

(a) Ionization isomers
(b) Linkage isomers
(c) Co-ordination isomers
(d) Geometrical isomers

24. The denticity of EDTA is : 

(a) Monodentate
(b) Hexadentate
(c) Bidentate
(d) Tridentate

25. An example of a sigma bonded organometallic compound is :

(a) Ruthenocene
(b) Grignard's reagent
(c) Ferrocene
(d) Cobaltocene

Answer 2

  1. Answer : (b) complex salt

Explanation: Potassium ferrocyanide is the inorganic compound with formula K₄[Fe(CN)₆]·3H₂O. It is the potassium salt of the coordination complex [Fe(CN)₆]⁴⁻. This salt forms lemon-yellow monoclinic crystals.

2. Answer : (a) Primary valency is ionisable

Explanation: Primary valency is ionisable according to Werner's theory of coordination compounds.
According to Werner's coordination theory, there are two kinds of valency, primary and secondary. The primary valency of a central metal ion is satisfied with anions.

3. Answer : (c) tetradentate

Explanation: Number of donor atoms in N(CH₂CH₂NH₂)₃ is four hence it is a tetradentate ligand.

4. Answer : (b) Oxalate

Explanation: In chelation, ring formation occurs because two atoms from the same ligand coordinate with the metal atom. This cannot happen if the ligand is monodentate.
Oxalate is a bidentate ligand hence it forms a chelate. It can coordinate with both of its negatively charged O atoms. Acetate, cyanide and ammonia are monodentate ligands. They do not form chelates.

5. Answer : (c) ONO

Explanation: Neutral ligand means ligand with no charge on it. Example: HO, NH₃, CO, C₂H₄. ONO₋ has charge on it, therefore it is not neutral ligand.

6. Answer : (d) SCN^–

Explanation: SCN- is a monodentate ligand hence cannot show chelation.

7. Answer : (d) [Co(NH₃)₃Cl₃]

Explanation: Optical isomerism is exhibited by only those complexes which lack elements of symmetry. [Co(NH₃)₃Cl₃] shows facial as well as meridional isomerism. But both the forms contain plane of symmetry. Thus, this complex does not exhibit optical isomerism.

8. Answer : (c) 3

Explanation: For the square planar complex [M_abcd] where M is the central atom and a,b,c,d are monodentate ligands, the number of possible geometrical isomers are three. In isomer I, C is opposite to A. In isomer II, D is opposite to A. In isomer III, B is opposite to A.

9. Answer : (d) d²sp³

Explanation: It involves sp³d² hybridization.

10. Answer : (a) 0

Explanation: Due to the presence of strong ligand, all the electrons get paired. So the number of unpaired electrons is 0.

11. Answer : (a) the formation of complex ion

Explanation: When mercuric iodide is dissolved in KI solution, it shows optical activity due to the complex formation. A complex called Nessler's reagent is formed.

12. Answer : (b) disodium salt of EDTA

Explanation: The hardness of water is estimated by simple titration of ethylene diamine tetraacetate (EDTA) solution. EDTA forms stable complexes with the metal ions present in the hard water since stability constants of calcium and magnesium complexes of EDTA are different, even the selective estimation of these ions is possible.

13. Answer : (a) cis-platin

Explanation: The chemical formula of Grignard reagent is R−MgX where Mg is a metal and R is any organic group. Hence, it is an organometallic compound. Therefore, the correct option is option B because cis-platin does not obey the criteria to be called an organometallic compound.

14. Answer : (a) primary valency is ionizable

Explanation: According to Werner theory for co-ordination compounds primary valency are ionizable.

15. Answer : (c) [CrCl₂(H₂O)₄] Cl . 2H₂O

Explanation: As 1/3 of total chlorine of the compound is precipitated by adding AgNO₃ to its aqueous solution so only one chloride ion is available for ionization, so compound is [CrCl₂(H₂O)₄] Cl.2H₂O.

16. Answer : (c) the number of ligands around a metal ion bonded by sigma bonds

Explanation: The number of atoms of the ligands that are directly bound to the central metal atom or ion by coordinate bonds is known as the coordination number of the metal atom or ion. Co-ordination number of metal = number of \(\sigma\)bonds formed by metal with ligands.

17. Answer : (d) hexadentate ligand

Explanation: [EDTA]^4- forms very stable complexes with most of the transition metals. This hexadentate ligand forms very stable complexes (usually octahedral structures) with most of the transition metals. The donor atoms in [EDTA]^4- are the two N atoms, and the four, negatively charged O atoms.

18. Answer : (b) 6

Explanation: Co- ordination number of Ni in [Ni(C₂O₄)₃]^4– is 6. This is because C₂O₂⁻⁴ (oxalate) is a bidentate ligand and thus, each coordinated with the central atom at two sites.

19. Answer : (b) basic in nature

Explanation: The ligands are basic in nature. They donate their lone pair of electrons to the central metal atom and form a coordinate bond.

20. Answer : (d) Thiocyanato

Explanation: Ambidentate ligand is a type of ligand which have the ability to bind to the central atom via the atoms of two different elements. Examples: thiocyanate ion(NCS^–) which can bind to the central metal atom or ion with either nitrogen or sulphur atoms.

21. Answer : (c) Bridging ligand

Explanation: It is a bidentate ligand having two NH donating groups . when both the lone pair of electrons are donating to metal atom then it behaves as bridging ligand. cobalt, nickel and zinc form complexes in which NH₂ -NH₂ acts as bridging ligand.

22. Answer : (b) NH₄

Explanation: In ammonia, N atom has one lone pair of electrons. Nitrogen donates this lone pair of electrons to proton to form ammonium ion. So NH₄⁺ ion does not have a lone pair of electrons which it can donate to central metal ion. Hence it cannot behave as a ligand.

23. Answer : (b) Linkage isomers

Explanation: The complex [Co(NH₃)₅(NO₂)]²⁺ and [Co(NH₃)₅ (ONO)]²⁺  are called linkage isomers due to presence of NO₂​ ligand.

24. Answer : (b) Hexadentate

Explanation: EDTA is a multidentate ligand. Its denticity (multiplicity) is 6. In EDTA, there are four Oxygen atoms and two Nitrogen atoms.

25. Answer : (b) Grignard's reagent 

Explanation: An example of a sigma bonded organometallic compound is Grignard's reagent. Whereas, ruthenocene, ferrocene and cobaltocene are not sigma bonded organometallic compound.

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