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NEET Chemistry · Co-ordination Compounds

Werner's theory, ligands, coordination number and chelation

Taught in NCERT Class 12 Chemistry, Chapter 5: Coordination Compounds.

2 verified questions: Easy 1 · Medium 1 · NEET level 0

Sample questions

Sample 1Easy

Ethane-1,2-diamine (en), when bound to a metal ion through both nitrogen atoms, acts as a

  1. A

    unidentate ligand

  2. B

    didentate ligand

  3. C

    ambidentate ligand

  4. D

    hexadentate ligand

Show the answer
The answer is B.

A ligand that binds through two donor atoms is didentate; H2NCH2CH2NH2 binds through its two nitrogen atoms. Such a ligand forms a ring with the metal and is a chelating ligand.

  • A.

    A unidentate ligand binds through one donor atom only, like NH3.

  • C.

    An ambidentate ligand can bind through either of two different atoms, like NO2- or SCN-; en uses both N atoms at once.

  • D.

    A hexadentate ligand has six donor atoms, like EDTA4-.

NCERT: Class 12 Chemistry, Unit 5 (Coordination Compounds), Definitions of Some Important Terms Pertaining to Coordination Compounds: Ligands

Sample 2Medium

One mole of the complex CoCl3·5NH3 reacts with excess AgNO3 solution to give two moles of AgCl. What is the correct formula of the complex?

  1. A

    [Co(NH3)4Cl2]Cl·NH3

  2. B

    [Co(NH3)5]Cl3

  3. C

    [Co(NH3)5Cl]Cl2

  4. D

    [Co(NH3)3Cl3]·2NH3

Show the answer
The answer is C.

Only chloride ions outside the coordination sphere are precipitated as AgCl. Two moles of AgCl means two ionisable Cl^-, so one Cl and five NH3 are bonded to Co, giving [Co(NH3)5Cl]Cl2 with coordination number 6.

  • A.

    This has only one ionisable chloride and would give one mole of AgCl.

  • B.

    This would give three moles of AgCl and gives Co a coordination number of 5 instead of 6.

  • D.

    This has no ionisable chloride and would give no AgCl.

NCERT: Class 12 Chemistry, Chapter 5, 5.1

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