Coordination Compounds — Page 6 | JEE Chemistry

Q51

Which one of the following complexes in an outer orbital complex?

A [Fe(CN)6]4-

B [Ni(NH3)6]2+

C [Co(NH3)6]3+

D [Mn(CN)6]4-

Correct Answer

Option B

Solution

Hybridisation

\mathop {{{\left[ {Fe{{\left( {CN} \right)}_6}} \right]}^{4 - }},}\limits_{{d^2}s{p^3}} \,\,\mathop {{{\left[ {Mn{{\left( {CN} \right)}_6}} \right]}^{4 - }},}\limits_{{d^2}s{p^3}}

\mathop {{{\left[ {Co{{\left( {N{H_3}} \right)}_3}} \right]}^{3 + }},}\limits_{{d^2}s{p^3}} \,\,\mathop {{{\left[ {Ni{{\left( {N{H_3}} \right)}_6}} \right]}^{2 + }}}\limits_{s{p^3}{d^2}}

Hence

{\left[ {Ni{{\left( {N{H_3}} \right)}_6}} \right]^{2 + }}

is outer orbital complex.

Q52

The IUPAC name of the coordination compound K3[Fe(CN)6] is

A Potassium hexacyanoferrate (II)

B Potassium hexacyanoferrate (III)

C Potassium hexacyanoiron (II)

D Tripotassium hexcyanoiron (II)

Correct Answer

Option B

Solution

{K_3}\left[ {Fe{{\left( {CN} \right)}_6}} \right]\,\,\,

is potassium hexacyano ferrate

\left( {{\rm I}{\rm I}{\rm I}} \right).

Q53

Which one of the following cyano complexes would exhibit the lowest value of paramagnetic behaviour? (At. No. Cr = 24, Mn = 25, Fe = 26, Co = 27)

A [Cr(CN)6]-3

B [Mn(CN)6]-3

C [Fe(CN)6]-3

D [Co(CN)6]-3

Correct Answer

Option D

Solution

No. of unpaired electron a) Co3+ 0 b) Fe3+ 1 c) Mn3+ 2 d) Cr3+ 3 The effective magnetic moment is given by the number of unpaired electrons in a substance, the lesser the number of unpaired electrons lower is its magnetic moment in Bohr $-$ Magneton and lower shall be its paramagnetism

Q54

The IUPAC name for the complex [Co(NO2)(NH3)5]Cl2 is

A nitrito-N-pentaamminecobalt (III) chloride

B nitrito-N-pentaamminecobalt (II) chloride

C pentaammine nitrito-N-cobalt (II) chloride

D pentaammine nitrito-N-cobalt (III) chloride

Correct Answer

Option D

Solution

The IUPAC name for the complex $[\text{Co(NO}_2)(\text{NH}_3)_5]\text{Cl}_2$ is: Pentaammine(nitrito- $\text{N,O}$ )cobalt(III) chloride Here's how to arrive at the name: The complex is a cobalt complex, and cobalt has a +3 charge in this compound (since it has one negatively charged NO $_2$ ligand and one negatively charged Cl ion, for a total of -2, to balance the +3 charge on cobalt).

The ligands are NH $_3$ (ammonia) and NO $_2$ (nitrito).

Ammonia is a neutral ligand, so its name is just "ammine" and it is designated by the prefix "penta" because there are five of them.

Nitrito is a negatively charged ligand, so its name is "nitrito- $\text{N,O}$ " (the "- $\text{N,O}$ " indicates that the NO $_2$ ligand is bound through both the nitrogen and oxygen atoms).

Finally, the compound has a chloride ion, so its name is "chloride" and it is designated by the prefix "di" because there are two of them.

Putting it all together, we get the name "pentaammine(nitrito- $\text{N,O}$ )cobalt(III) chloride".

Q55

How many EDTA (ethylenediaminetetraacetic acid) molecules are required to make an octahedral complex with a Ca2+ ion?

A Six

B Three

C One

D Two

Correct Answer

Option C

Solution

EDTA

has hexadentate four donar

O

atoms and

2

donar

N

atoms and for the formation of octahedral complex one molecule is required

Q56

In Fe(CO)5, the Fe – C bond possesses :

A π-character only

B both

\sigma

and π characters

C ionic character

D

\sigma

-character

Correct Answer

Option B

Solution

Due to some back-bonding by side-wise overlapping of between

d

-orbitals of metal and

p

-orbital of carbon, the

Fe-C

bond in

Fe{\left( {CO} \right)_5}

has both $\sigma$ and $\pi$ character.

Q57

Nickel (Z = 28) combines with a uninegative monodentate ligand X– to form a paramagnetic complex [NiX4]2− . The number of unpaired electron(s) in the nickel and geometry of this complex ion are, respectively

A one, tetrahedral

B two, tetrahedral

C one, square planar

D two, square planar

Correct Answer

Option B

Solution

{\left[ {Ni{X_4}} \right]^{2 - }},

the electronic configuration of

N{i^{2 + }}

is It contains two unpaired electrons and the hybridisation is

s{p^3}

(tetrahedral).

Q58

Which one of the following has a square planar geometry?

A [CoCl4]2-

B [FeCl4]2-

C [NiCl4]2-

D [PtCl4]2-

Correct Answer

Option D

Solution

Complexes with

ds{p^2}

hybridisation are square planar. So

\,\,{\left[ {PtC{l_4}} \right]^{2 - }}\,\,

is square planar in shape.

Q59

In which of the following octahedral complexes of Co (at. no. 27), will the magnitude of

\Delta _o

be the highest?

A [Co(CN)6]3−

B [Co(C2O4)3]3−

C [Co(H2O)6]3+

D [Co(NH3)6]3+

Correct Answer

Option A

Solution

In octahedral complex the magnitude of

{\Delta _o}

will be highest in a complex having strongest ligand. Of the given ligands

C{N^ - }

is strongest so

{\Delta _o}

will be highest for

{\left( {Co{{\left( {CN} \right)}_6}} \right)^{3 - }}.

Thus option

(a)

is correct.

Q60

The coordination number and the oxidation state of the element ‘E’ in the complex [E(en)2(C2O4)]NO2 (where (en) is ethylene diamine) are, respectively,

A 6 and 2

B 4 and 2

C 4 and 3

D 6 and 3

Correct Answer

Option D

Solution

In the given complex we have two bidentate ligands (i.e.

en

and

{C_2}{O_4}

), so coordination number of

E

is

6

\left( {2 \times 2 + 1 \times 2 = 6} \right)

Let the oxidation state of

E

in complex be

x,

then

\left[ {x + \left( { - 2} \right) = 1} \right]

or

x - 2 = 1

or

\,\,\,\,

x=+3,

so its oxidation state is

+3

Thus option

(d)

is correct.