Q: In the complex ion \$[Fe(EDTA)]^-\$ the coordination number and oxidation state of central metal ion is:

In \$[Fe(EDTA)]^-\$, the denticity of EDTA=6, so the co-ordination number \$=6\$.The change of EDTA\$=-4\$Let oxidation state of Fe is n.\$\Rightarrow n-4=-1\$\$n=+3\$\$\Rightarrow C.N=6;\ Oxidation\ number =+3\$

Q: Which of the following is not a neutral ligand?

Neutral ligand means ligand with no charge on it.Example: \$H_2O,NH_3,CO,C_2H_4...\$ \$ONO^-\$ has charge on it,therefore it is not neutral ligand.Hence option C is correct.

Question 1

What is meant by the chelate effect? Give an example.

Accepted Answer

Chelate effect represents the stabilization of coordination compounds due to formation of metal chelates. Complexes containing chelating ligands are more stable than complexes containing unidentate ligands. Thus, $\displaystyle [Co(en)3]^{3+}$ is more stable than $\displaystyle [Co(NH_3)_6]^{3+}$. Here, en is ethylene diammine, a bidentate ligand.

Question 2

Which of the following ligands form a chelate?

Accepted Answer

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.

Question 3

In the complex ion $[Fe(EDTA)]^-$ the coordination number and oxidation state of central metal ion is:

Accepted Answer

In $[Fe(EDTA)]^-$, the denticity of EDTA=6, so the co-ordination number $=6$.The change of EDTA$=-4$Let oxidation state of Fe is n.$\Rightarrow  n-4=-1$$n=+3$$\Rightarrow C.N=6;\ Oxidation\ number =+3$

Question 4

What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each.

Accepted Answer

Unidentate  ligand: Only one donor site is present. Examples includes ammonia and chloride ions.Bidentate ligand:Two donor sites are present. Examples include ethylene diammine and oxalate ion Ambidentate ligand:Ligands can coordinate to a central metal through two different sites.Examples include (1) nitro group ($N$ as donor atom) and nitrito group ($O$ as donor atom)(2) Thiocyanate ($S$ atom as donor atom) and isothiocyanate ($N$ atom as donor atom).

Question 5

What  are primary valencies and secondary valencies give an example?

Accepted Answer

The primary valency is the number of negative ions which are equivalent to the charge on the metal ion. The secondary valency is the number of ligands that are attached or coordinated to metal ion. For e.g, $[Cr(H_2O)_6]Cl_3$. The primary valency in this coordination complex is 3 and the secondary valency is 6.

Question 6

Which of the following method is used to estimate the hardness of water?

Accepted Answer

The hardness of water can be determined by complexometric titration using Ethylene diamine tetraacetic acid  (EDTA). EDTA in the form of its di-sodium salt forms complex with  $Ca^{2+}$ and $Mg^{2+}$ ions of the water sample.  When  Eriochrome  Black  T (EBT) indicator is added to the hard water at pH around 9.10, it gives wine red coloured unstable complex with $Ca^{2+}$ and $Mg^{2+}$ ions of the water sample.

Question 7

Which of the following is not a chelating agent?

Accepted Answer

Oxalato, glycinato and ethylene diamine are large ligands and they can form rings because they all are bidentate ligands. So, they all are also chelating ligands. Thiosulphato is a monodentate ligand and hence, cannot form chelate rings. So, it is not a chelating ligand.

Question 8

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

Accepted Answer

Complexes are formed when ligands donate a pair of electrons to metals. In ammonia, N atom has one lone pair of electrons. Nitrogen donates this lone pair of electrons to proton to form ammonium ion. So $NH_4^+$ ion does not have a lone pair of electrons which it can donate to central metal ion. Hence it cannot behave as a ligand.

Question 9

Write the formulas for the following coordination compounds:Potassium tetracyanonickelate(II)

Accepted Answer

The formula of the coordination compound Potassium tetracyanonickelate(II) is $ K_2[Ni(CN)_4]$.Tetracyano means 4 CN groups.

Question 10

Which of the following is not a neutral ligand?

Accepted Answer

Neutral ligand  means ligand with no charge on it.Example: $H_2O,NH_3,CO,C_2H_4...$  $ONO^-$ has charge on it,therefore it is not neutral ligand.Hence option C is correct.

Revise with Concepts

Basics of coordination chemistry

Quick Summary With Stories

Types of Complexes

What is meant by the chelate effect? Give an example.

Which of the following ligands form a chelate?

In the complex ion $[F e (E D T A)]^{-}$ the coordination number and oxidation state of central metal ion is:

What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each.

What are primary valencies and secondary valencies give an example?

Which of the following method is used to estimate the hardness of water?

Which of the following is not a chelating agent?

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

Write the formulas for the following coordination compounds:
Potassium tetracyanonickelate(II)

Which of the following is not a neutral ligand?

Revise with Concepts

Basics of coordination chemistry

Quick Summary With Stories

Types of Complexes

What is meant by the chelate effect? Give an example.

Which of the following ligands form a chelate?

In the complex ion [Fe(EDTA)]− the coordination number and oxidation state of central metal ion is:

What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each.

What are primary valencies and secondary valencies give an example?

Which of the following method is used to estimate the hardness of water?

Which of the following is not a chelating agent?

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

Write the formulas for the following coordination compounds: Potassium tetracyanonickelate(II)

Which of the following is not a neutral ligand?

In the complex ion $[F e (E D T A)]^{-}$ the coordination number and oxidation state of central metal ion is:

Write the formulas for the following coordination compounds:
Potassium tetracyanonickelate(II)