The d- and f- Block Elements Test

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The d- and f- Block Elements Test - 41

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is diamagnetic ion?

A
$$Zn^{2+}$$

B
$$Ni^{2+}$$

C
$$Co^{2+}$$

D
$$Cu^{2+}$$

Solution

$${ Zn }^{ 2+ }\equiv \left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 6 }{ 4s }^{ 0 }{ 3d }^{ 10 }$$
It is diamagnetic, so no unpaired $${ e }^{ - }s$$.
Question 2
1 / -0

$$\mu = \sqrt{15}$$ is true for the pair:

A
$$Co^{+2}, Cr^{+3}$$

B
$$Fe^{+2}, Cr^{+3}$$

C
$$Fe^{+3}, Cr^{+2}$$

D
$$Mn^{+2}, Fe^{+2}$$

Solution

The electronic configuration of $$Co^{2+}$$ is;$$[Ar]4s^0 3d^7$$
Hence there are three unpaired electrons in $$Co^{2+}$$
Now the elctronic configuration of $$Cr^{3+}$$ is;$$[Ar]3d^3$$
Hence there are 3 unpaired electrons in $$Cr^{3+}$$
We know magnetic moment $$\mu=\sqrt{(n(n+2)}$$$$
where n is number of unpaired electrons.
So when n=3,
$$\mu=\sqrt{(3(3+2)}=\sqrt{15}$$
Hence option A is correct answer.
Question 3
1 / -0

Atomic number of three elements A, B, and C are respectively,

$$Pm\ (Z=61),\ Sm\ (Z=62),\ Eu\ (Z=63).$$

Which one has a maximum atomic radius?

A
A

B
B

C
C

D
All have the same radius

Solution
Question 4
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Which of the following paramagnetic ions would exhibit magnetic moment (Spin only) of the order 5 BM? (Atomic number Mn = 25, Cr = 24, V = 23, Ti = 22)

A
$$V^{2+}$$

B
$$Ti^{2+}$$

C
$$Mn^{+2}$$

D
$$Cr^{2+}$$

Solution

Configuration of ,
$$V^{2+}[Ar]4s^03d^3$$ $$n=3$$
$$Ti^{2+}[Ar]4s^03d^2$$ $$n=2$$
$$Mn^{2+}[Ar]4s^03d^5$$ $$n=5$$
$$Cr^{2+}[Ar]4s^03d^4$$ $$n=4$$
Hence spin moment of $$Cr^{2+}=\sqrt{4(4+2)}\simeq4.92BN\simeq5BM$$
Question 5
1 / -0

The ratio of number of exchange pairs present in $$d^{9}$$ and magnetic moment of Cr in B.M. is:-

A
$$\frac{2}{\sqrt{3}}$$

B
$$\frac{2\sqrt{3}}{3}$$

C
$$\frac{2\sqrt{3}}{4}$$

D
$$\frac{16}{\sqrt{35}}$$

Solution

Magnetic moment of $$Cr$$ in $$d^9$$:
$$\mu=\sqrt {n(n+2)}$$
$$=\sqrt {1(1+2)}=\sqrt {3}$$ (Refer to Image)
Two exchange pairs present in $$d^9$$ of $$Cr$$:
$$\therefore \cfrac {2}{\sqrt {3}}$$ .
Question 6
1 / -0

Amongst the following ions, which is considered as most stable in $${ M }^{ 2+ }$$ state?

A
$${ Ti }^{ 2+ }/Ti\left( -1.63V \right) $$

B
$${ V }^{ 2+ }/V\left( -1.11V \right) $$

C
$${ Cr }^{ 2+ }/Cr\left( -0.90V \right) $$

D
$${ Mn }^{ 2+ }/Mn\left( 1.18V \right) $$

Solution

Half reactions with lowest standard reduction have stable reactants (ions).
Here, $$Ti^{2+}+2e^-\longrightarrow Ti\ [Reduction]$$
The standard reduction potential of this reaction is least. So, the reactant $$Ti^{2+}$$ is more stable.
Question 7
1 / -0

Which of the following pairs of atom have the most similar radii ?

A
$$Zr, Hf$$

B
$$Cu, Ag$$

C
$$Sc, Ti$$

D
$$Pd, Pt$$
Question 8
1 / -0

Which of the following will be paramagnetic?

A
$$O_{2}^{2-}$$

B
$$Cr^{3+}$$

C
$$Na^{+}$$

D
$$Cu^{+}$$
Solution
- Configuration of $$Cr^{3+}$$ is:$$[Ar]3d^3$$
- Since there are five-3d orbitals, they are not all at least singly filled yet, and thus, all three electrons in the lowest-energy configuration are unpaired. So, this is paramagnetic.
Question 9
1 / -0

Which of the following ions in its aqueous solution possesses the value of magnetic moment as $$3.87$$?

A
$$Cu^{2+}$$

B
$$Cu^{3+}$$

C
$$Co^{3+}$$

D
$$Fe^{3+}$$

Solution
Question 10
1 / -0

Which of the following complex compounds will exibit highest paramagnetic behavior?

A
$$[Ti({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

B
$$[Cr({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

C
$$[Co({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

D
$$[{ Zn }(NH_{ 3 }{ ) }_{ 4 }{ ] }{ Cl }_{ 2 }$$

Solution

$${ T }i^{ 3+ }-\left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 6 }{ 4s }^{ 0 }{ 3d }^{ 1 }$$
$${ Zn }^{ 2+ }-\left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 6 }{ 4s }^{ 0 }{ 3d }^{ 10 }\quad \} -$$ not much paramagnetic
$${ Cr }^{ 3+ }\rightarrow { d }_{ 3 }$$ configuration $$\rightarrow { t }_{ 2 g}$$ means paramagnetic
$${ Co }^{ 3+ }\rightarrow { d }_{ 6 }$$ configuration $$\rightarrow { NH }_{ 3 }$$ strong field ligand
So, it would be $${ d }_{ 6 }$$ (low spin) diamagnetic.

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The d- and f- Block Elements Test - 41

Result

The d- and f- Block Elements Test - 41

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Question 1

$$Zn^{2+}$$

$$Ni^{2+}$$

$$Co^{2+}$$

$$Cu^{2+}$$

Solution

Question 2

$$Co^{+2}, Cr^{+3}$$

$$Fe^{+2}, Cr^{+3}$$

$$Fe^{+3}, Cr^{+2}$$

$$Mn^{+2}, Fe^{+2}$$

Solution

Question 3

A

B

C

All have the same radius

Solution

Question 4

$$V^{2+}$$

$$Ti^{2+}$$

$$Mn^{+2}$$

$$Cr^{2+}$$

Solution

Question 5

$$\frac{2}{\sqrt{3}}$$

$$\frac{2\sqrt{3}}{3}$$

$$\frac{2\sqrt{3}}{4}$$

$$\frac{16}{\sqrt{35}}$$

Solution

Question 6

$${ Ti }^{ 2+ }/Ti\left( -1.63V \right) $$

$${ V }^{ 2+ }/V\left( -1.11V \right) $$

$${ Cr }^{ 2+ }/Cr\left( -0.90V \right) $$

$${ Mn }^{ 2+ }/Mn\left( 1.18V \right) $$

Solution

Question 7

$$Zr, Hf$$

$$Cu, Ag$$

$$Sc, Ti$$

$$Pd, Pt$$

Question 8

$$O_{2}^{2-}$$

$$Cr^{3+}$$

$$Na^{+}$$

$$Cu^{+}$$

Solution

Question 9

$$Cu^{2+}$$

$$Cu^{3+}$$

$$Co^{3+}$$

$$Fe^{3+}$$

Solution

Question 10

$$[Ti({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

$$[Cr({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

$$[Co({ NH }_{ 3 }{ ) }_{ 6 }{ ] }^{ 3+ }$$

$$[{ Zn }(NH_{ 3 }{ ) }_{ 4 }{ ] }{ Cl }_{ 2 }$$

Solution

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