Coordination Compounds Class 12 Chemistry Free Online Mock Test 1

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Coordination Compounds Online Mock Test Class 12 Chemistry

1 / 20

(a) K, L, M, N

(b) K, M, O, P

(c) L, M, O, P

(d) L, M, N, O

2 / 20

Which of the above complexes obey $E A N$ rule?

1, 2

2,3,4

1,2,3,4

None of these

3 / 20

A

B

C

D

4 / 20

Match the geometry (given in column A) with the complexes (given in column B)

I-P, II-Q, III-R

I-R, II-P, III-Q

I-R, II-Q, III-P

I-Q, II-P, III-R

5 / 20

Arrange the following in order of decreasing number of unpaired electrons:

I V , I , I I , I I I

I , I I , I I I , I V

I I I , I I , I , I V

I I , I I I , I , I V

Solution

The correct option is A $I V, I, I I, I I I$
Option (A) is correct.
$I$ : $[F e (H_{2} O)_{6}]^{2 +}$ contains 4 unpaired electrons.
$I I$ : $[F e (C N)_{6}]^{3 -}$ contains 1 unpaired electron.
$I I I$ : $[F e (C N)_{6}]^{4 -}$ contains 0 unpaired electron.
$I V$ : $[F e (H_{2} O)_{6}]^{3 +}$ contains 5 unpaired electrons.

6 / 20

Increasing value of magnetic moment for the given compounds is:
(I) $[F e (C N)_{6}]^{4 -}$
(II) $[F e (C N)_{6}]^{3 -}$
(III) $[C r (N H_{3})_{6}]^{3 +}$
(IV) $[N i (H_{2} O)_{6}]^{2 +}$

I < II < III < IV

IV < III < II < I

II< III < I < IV

I < II < IV < III

Solution

The correct option is D I < II < IV < III
No. of unpaired electrons in:
$[F e (C N)_{6}]^{4 -}$ is 0
$[F e (C N)_{6}]^{3 -}$ is 1
$[N i (H_{2} O)_{6}]^{2 +}$ is 2
$[C r (N H_{3})_{6}]^{3 +}$ is 3
As the number of unpaired electrons increases, magnetic moment increases.

7 / 20

Order of number of chelate ring is correct for:

iii > i > ii > iv

iii > ii > i > iv

iii > iv > i > ii

ii > iii > i > iv

8 / 20

The correct order spin-only magnetic moments of the following complexes is:

( I I I ) > ( I ) > ( I I ) > ( I V )

( I I I ) > ( I ) > ( I V ) > ( I I )

( I ) > ( I V ) > ( I I I ) > ( I I )

( I I ) ≈ ( I ) > ( I V ) > ( I I I )

Solution

The correct option is C $(I) > (I V) > (I I I) > (I I)$
Complex (I) has the central metal ion as $C r^{2 +}$ with weak field ligands. Configuration of $C r^{2 +} = [A r] 3 d^{4}$
As weak field ligands are present, pairing does not take place. There will be 4 unpaired electrons and hence the magnetic moment $\sqrt{24} B.M$

Complex (II) has the central metal ion as $F e^{2 +}$ with strong field ligands. Configuration of $F e^{2 +} = [A r] 3 d^{6}$
Strong field ligands will pair up all the electrons and hence the magnetic moment will be zero.

Complex (III) has the central metal ion as $F e^{3 +}$ with strong field ligands.
Configuration of $F e^{3 +} = [A r] 3 d^{5}$
As it is given that $Δ_{0} > P$ hence the electrons will pair up but as we have a $[A r] 3 d^{5}$ configuration, one electron will remain unpaired and hence the magnetic moment will be $\sqrt{3} B.M$ .

Complex (IV) has the central metal ion as $C o^{2 +}$ with weak field ligands.
Configuration of $C o^{2 +} = [A r] 3 d^{7}$
As weak field ligands are present no pairing can occur. There will be 3 unpaired electrons and hence the magnetic moment $\sqrt{15} B.M$

9 / 20

The value of the ‘spin only’ magnetic moment for one of the following configurations is 2.84 BM. The correct one is

(a) d5 (in strong ligand field)

(b) d3 (in weak as well as strong ligand fields)

(c) d4 (in weak ligand field)

(d) d4 (in strong ligand field)

Answer: Introduction: Spin-only magnetic moment is the magnetic moment of a coordination compound that arises due to the net spin of the unpaired electrons present in the d-orbitals of the central metal ion. Explanation: The spin-only magnetic moment of a coordination compound can be calculated using the following formula: µS = √n(n+2)BM where, n is the number of unpaired electrons and BM is the Bohr magneton. (a) d⅝5 (in strong ligand field): The number of unpaired electrons in d⅝5 is 5. In strong ligand field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d⅝5 in strong ligand field will be less than 2.84 BM. Hence, option (a) is not correct. (b) d³ (in weak as well as in strong fields): The number of unpaired electrons in d³ is 3. The spin-only magnetic moment of d³ in weak field is given by: µS = √3(3+2)BM = 3.87 BM In strong field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d³ in strong ligand field will be less than 3.87 BM. Hence, option (b) is not correct. (c) d⁴ (in weak ligand fields): The number of unpaired electrons in d⁴ is 2. The spin-only magnetic moment of d⁴ in weak field is given by: µS = √2(2+2)BM = 2.83 BM This value is close to 2.84 BM. Therefore, option (c) can be considered as correct. (d) d⁴ (in strong ligand fields): In strong ligand field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d⁴ in strong ligand field will be less than 2.83 BM. Hence, option (d) is not correct. Conclusion: Hence, the correct option is (c) d⁴ (in weak ligand fields).

10 / 20

The correct order of magnetic moments (spin only value in BM) among, the following is (Atomic number Mn=25, Fe=26, Co=27)

(a) [MnCl4]2- > [CoCl4]2- > [Fe(CN)6]4-

(b) [MnCl4]2- > [Fe(CN)6]4- > [CoCl]2-

(c) [Fe(CN)6]4- > [MnC4]2- > [CoCl4]2-

(d) [Fe(CN)6]4- > [CoCl4]2- > [MnCl4]2-

Solution

The correct option is A $[M n C l_{4}]^{2 -} > [C o C l_{4}]^{2 -} > [F e (C N)_{6}]^{4 -}$
$[F e (C N)_{6}]^{4 -} \to F e^{2 +} \to [A r] 3 d^{6}$
(Due to strong field ligand of $(C N^{-})$ all unpaired electrons get paired.)
$[M n C l_{4}]^{2 -} \to M n^{2 +} \to [A r] 3 d^{5}$
(due to weak field ligand of $(C l^{-})$ no change in unpaired electrons
$[C o C l_{4}]^{2 -} \to C o^{2 +} \to [A r] 3 d^{7}$
(Due to weak field ligand of $(C l^{-})$ no change in unpaired electrons)
Magnetic moment $= \sqrt{n (n + 2)} B . M .$
Where, n = number of unpaired electrons.
In $[M n C l_{4}]^{2 -}$ , $M n$ contains maximum no. of electrons
So, order of magnetic moment $[M n C l_{4}]^{2 -} > [C o C l_{4}]^{2 -} > [F e (C N)_{6}]^{4 -}$

11 / 20

A complex compound of Co³⁺ with molecular formula CoCl_x.yNH3 gives a total of 3 ions when dissolved in water. How many Cl^– ions satisfy both primary and secondary valencies in this complex?

4

3

2

1

In coordination compounds, the primary valency is the number of negative ions that are equivalent to the charge on the metal ion, while the secondary valency is the number of ligands attached to the metal ion:

Primary valency
Definition: The number of negative ions equivalent to the charge on the metal ion
Value: Usually a positive value, but can be zero
Satisfaction: Only satisfied by negatively charged ligands
Directionality: Non-directional
Notation: Dotted lines

Secondary valency
Definition: The number of ligands attached to the metal ion
Satisfaction: Can be satisfied by a neutral molecule, a negatively charged species, or a positively charged species
Directionality: Directional
Notation: Dark or straight lines

The coordination number of cobalt in $C o^{3} +$ will be '6' Siince the given compound gives 3 ions when dissolved in water , its structural formula should be $[C o c l {(N H 3)}_{5}] C l_{2}$
$[C o C l {(N h 3)}_{5}] C l_{2} = {[C o C l_{3}]}_{3}^{2} + + 2 C l^{-}$
therefroe , only one chlorine atom satisfies both primary and secondary valency of $C o^{3+}$ .

12 / 20

The magnetic moment of K₃[Fe(CN)₆] is found to be 1.7 BM. How many unpaired electrons(s) is/are present per molecule?

1

2

3

4

13 / 20

The d-electron configurations of Cr²⁺, Mn²⁺, Fe²⁺ and Ni²⁺ are 3d⁴, 3d⁵, 3d⁶ and 3d⁸ respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behavior? (Atomic number Cr=24, Mn=25, Fe=26, Ni=28)

a) [Mn(H2O)6]2+

(b) [Fe(H2O)6]2+

(c) [Ni(H2O)6]2+

(d) [Cr(H2O)6]2+

14 / 20

Why do compounds having similar geometry have different magnetic moment?

(a) Due to different reactivity

(b) Due to their labile nature

(c) Due to the presence of weak and strong field ligands

(d) None of the above

15 / 20

According to werner’s theory :

A) Primary Valeccy can be ionized

(B) Secondary valency can be ionized

(C) Primary and secondary valencies cannot be ionized

(D) Only primary valency cannot be ionized

(a) Primary valency- This is ionizable and is satisfied by the negative charges. In werner coordination theory the primary valency corresponds to the oxidation state of the central transition metal ion and it is always preferred to satisfied by the negative charged ions . On the other hand the secondary valency corresponds to the coordination number of the metal complex.

16 / 20

Which is the example of hexadentate ligand ?

(A) 2,2-dipyridyl

(B) Dimethyl glyoxime

(C) Aminodiacetate ion

(D) Ethylene diammine tetra actate ion

17 / 20

Given the molecular formula of the hexa coordinated complexes.

(A) CoCl3 6NH₃

(B) CoCl3 5NH₃

(C) CoCl3 4NH₃

If the number of coordinated NH₃ molecules in A,B and C respectively are 6,5 and 4 the primary valency (A), (B) and (C) are:

(A) 6,5,4

(B) 3,2,1

(C) 0,1,2

(D) 3,3,3

18 / 20

Coordination number of Ni in [Ni(C₂O₄)₃]^4- is

5

4

6

3

19 / 20

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 bonds

(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 and pi bonds both

(d) the number of only anionic ligands bonded to the metal ion

The co-ordination number of a central metal atom in a complex is determined by the number of ligands around a metal ion bonded by sigma bonds. It is also define as the number of atoms, ions, or molecules that a central atom or ion holds as its nearest neighbors in a complex.

20 / 20

Which of the following statements about coordination compounds’ bonding is incorrect?

a) Crystal Field Theory

b) VSEPR Theory

c) Valence Bond Theory

d) Molecular Orbital Theory

Answer: b

Explanation: The VSEPR Theory uses electron pairs in atoms to explain the structure of particular molecules. The theories VBT, CFT, LFT, and MOT explain the nature of bonding in coordination compounds.

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