Chapter 5: Coordination Compounds Assertion-Reason Questions | chemistry Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): 1 mol of CoCl3·6NH3 (yellow) precipitates 3 mol AgCl on adding excess AgNO3. Reason (R): In [Co(NH3)6]3+3Cl–, all three chloride ions are present as counter ions outside the coordination sphere and are freely ionisable.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): Double salts dissociate completely into simple ions in aqueous solution. Reason (R): In double salts, the constituent compounds are held together by secondary valences which are non-ionisable.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): EDTA4– is a hexadentate ligand. Reason (R): EDTA4– can bind to a central metal ion through two nitrogen atoms and four oxygen atoms simultaneously.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 4

Logic Check

Assertion (A): [Ni(CN)4]2– is diamagnetic while [NiCl4]2– is paramagnetic. Reason (R): CN– is a strong field ligand that causes pairing of electrons, while Cl– is a weak field ligand that does not cause pairing.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): Tetrahedral complexes almost always form high spin configurations. Reason (R): The crystal field splitting energy in tetrahedral geometry is Δt = (4/9)Δo, which is smaller than the electron pairing energy in most cases.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): Anhydrous CuSO4 is white, but CuSO4·5H2O is blue. Reason (R): In the absence of ligands, no crystal field splitting occurs, so no d-d transition is possible and the compound is colourless.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): [Co(NH3)6]3+ is an inner orbital complex. Reason (R): NH3 is a strong field ligand that causes pairing of 3d electrons, enabling d2sp3 hybridisation using inner 3d orbitals.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): Geometrical isomerism is not possible for tetrahedral complexes of the type [MX2L2]. Reason (R): All positions in a tetrahedron are adjacent to each other, so all ligands occupy equivalent positions relative to each other.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 9

Logic Check

Assertion (A): [Co(en)3]3+ is optically active. Reason (R): [Co(en)3]3+ has a centre of symmetry that makes it superimposable on its mirror image.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 10

Logic Check

Assertion (A): The coordination number of Fe in [Fe(C2O4)3]3– is 6. Reason (R): C2O42– is a didentate ligand, each contributing 2 donor atoms, so 3 × 2 = 6 donor atoms bond to Fe.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): Chelate complexes are generally more stable than similar complexes with unidentate ligands. Reason (R): Chelate complex formation leads to an increase in entropy due to release of multiple unidentate ligands, making the process thermodynamically more favourable.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): [Fe(H2O)6]3+ is strongly paramagnetic while [Fe(CN)6]3– is weakly paramagnetic. Reason (R): H2O is a strong field ligand that causes greater splitting than CN–.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 13

Logic Check

Assertion (A): NO2– is an ambidentate ligand. Reason (R): NO2– can coordinate either through nitrogen (–NO2) or through oxygen (–ONO) to the central metal atom.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): The metal-carbon bond in metal carbonyls has both σ and π character. Reason (R): CO donates its lone pair to the metal (σ bond) and the metal donates electrons from its filled d orbital to the π* orbital of CO (π back-bonding), creating a synergic effect.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): [Ni(CO)4] is diamagnetic while [NiCl4]2– is paramagnetic, though both are tetrahedral. Reason (R): In [Ni(CO)4], Ni is in zero oxidation state (3d10) with no unpaired electrons; in [NiCl4]2–, Ni2+ (3d8) with weak field Cl– retains 2 unpaired electrons.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 16

Logic Check

Assertion (A): Vitamin B12 is a coordination compound of cobalt. Reason (R): Vitamin B12 (cyanocobalamine) is used in the treatment of pernicious anaemia and has Co3+ as the central metal ion.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): The primary valences of a metal in coordination compounds are ionisable. Reason (R): Primary valences are satisfied by neutral ligands such as NH3 and H2O that donate electron pairs.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): Octahedral complexes of the type [MA3B3] can show fac and mer geometrical isomers. Reason (R): In the fac isomer, three identical ligands occupy adjacent positions at the corners of one face; in the mer isomer, they occupy positions around the meridian.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 19

Logic Check

Assertion (A): In CFT, the eg set of d orbitals is raised in energy in an octahedral field. Reason (R): The dx2–y2 and dz2 orbitals point directly towards the ligands along the axes, experiencing greater repulsion from ligand electrons.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 20

Logic Check

Assertion (A): The complex [CoCl2(en)2]+ shows both geometrical and optical isomerism. Reason (R): The trans isomer of [CoCl2(en)2]+ shows optical isomerism while the cis isomer does not.

Reasoning Options

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Chapter sections

Chapter 5: Coordination Compounds | Assertion-Reason

Assertion (A): 1 mol of CoCl3·6NH3 (yellow) precipitates 3 mol AgCl on adding excess AgNO3. Reason (R): In [Co(NH3)6]3+3Cl–, all three chloride ions are present as counter ions outside the coordination sphere and are freely ionisable.

Assertion (A): Double salts dissociate completely into simple ions in aqueous solution. Reason (R): In double salts, the constituent compounds are held together by secondary valences which are non-ionisable.

Assertion (A): EDTA4– is a hexadentate ligand. Reason (R): EDTA4– can bind to a central metal ion through two nitrogen atoms and four oxygen atoms simultaneously.

Assertion (A): [Ni(CN)4]2– is diamagnetic while [NiCl4]2– is paramagnetic. Reason (R): CN– is a strong field ligand that causes pairing of electrons, while Cl– is a weak field ligand that does not cause pairing.

Assertion (A): Tetrahedral complexes almost always form high spin configurations. Reason (R): The crystal field splitting energy in tetrahedral geometry is Δt = (4/9)Δo, which is smaller than the electron pairing energy in most cases.

Assertion (A): Anhydrous CuSO4 is white, but CuSO4·5H2O is blue. Reason (R): In the absence of ligands, no crystal field splitting occurs, so no d-d transition is possible and the compound is colourless.

Assertion (A): [Co(NH3)6]3+ is an inner orbital complex. Reason (R): NH3 is a strong field ligand that causes pairing of 3d electrons, enabling d2sp3 hybridisation using inner 3d orbitals.

Assertion (A): Geometrical isomerism is not possible for tetrahedral complexes of the type [MX2L2]. Reason (R): All positions in a tetrahedron are adjacent to each other, so all ligands occupy equivalent positions relative to each other.

Assertion (A): [Co(en)3]3+ is optically active. Reason (R): [Co(en)3]3+ has a centre of symmetry that makes it superimposable on its mirror image.

Assertion (A): The coordination number of Fe in [Fe(C2O4)3]3– is 6. Reason (R): C2O42– is a didentate ligand, each contributing 2 donor atoms, so 3 × 2 = 6 donor atoms bond to Fe.

Assertion (A): Chelate complexes are generally more stable than similar complexes with unidentate ligands. Reason (R): Chelate complex formation leads to an increase in entropy due to release of multiple unidentate ligands, making the process thermodynamically more favourable.

Assertion (A): [Fe(H2O)6]3+ is strongly paramagnetic while [Fe(CN)6]3– is weakly paramagnetic. Reason (R): H2O is a strong field ligand that causes greater splitting than CN–.

Assertion (A): NO2– is an ambidentate ligand. Reason (R): NO2– can coordinate either through nitrogen (–NO2) or through oxygen (–ONO) to the central metal atom.

Assertion (A): The metal-carbon bond in metal carbonyls has both σ and π character. Reason (R): CO donates its lone pair to the metal (σ bond) and the metal donates electrons from its filled d orbital to the π* orbital of CO (π back-bonding), creating a synergic effect.

Assertion (A): [Ni(CO)4] is diamagnetic while [NiCl4]2– is paramagnetic, though both are tetrahedral. Reason (R): In [Ni(CO)4], Ni is in zero oxidation state (3d10) with no unpaired electrons; in [NiCl4]2–, Ni2+ (3d8) with weak field Cl– retains 2 unpaired electrons.

Assertion (A): Vitamin B12 is a coordination compound of cobalt. Reason (R): Vitamin B12 (cyanocobalamine) is used in the treatment of pernicious anaemia and has Co3+ as the central metal ion.

Assertion (A): The primary valences of a metal in coordination compounds are ionisable. Reason (R): Primary valences are satisfied by neutral ligands such as NH3 and H2O that donate electron pairs.

Assertion (A): Octahedral complexes of the type [MA3B3] can show fac and mer geometrical isomers. Reason (R): In the fac isomer, three identical ligands occupy adjacent positions at the corners of one face; in the mer isomer, they occupy positions around the meridian.

Assertion (A): In CFT, the eg set of d orbitals is raised in energy in an octahedral field. Reason (R): The dx2–y2 and dz2 orbitals point directly towards the ligands along the axes, experiencing greater repulsion from ligand electrons.

Assertion (A): The complex [CoCl2(en)2]+ shows both geometrical and optical isomerism. Reason (R): The trans isomer of [CoCl2(en)2]+ shows optical isomerism while the cis isomer does not.

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