The d- and f- Block Elements Test

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The d- and f- Block Elements Test - 40

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Weekly Quiz Competition

Question 1
1 / -0

The ratio of magnetic moments of $$Fe(III)$$ and $$Co(II)$$ is:

A
$$7 : 3$$

B
$$3 : 7$$

C
$$\sqrt7 : \sqrt3$$

D
$$\sqrt3 : \sqrt7$$

Solution

Electronic configuration of $$Fe^{3+}:[Ar]3d^54s^0$$
So number of unpaired elctrons is $$n=5$$
Hence, $$\mu=\sqrt{n(n+2)}=\sqrt{35}$$
Now,
Electronic configuration of $$Co^{2+}:[Ar]3d^74s^0$$
So number of unpaired electros is $$n=3$$
Hence, $$\mu=\sqrt{n(n+2)}=\sqrt{15}$$
So, Ratio of Magnetic moments of $$Fe^{3+}$$ and $$Co^{2+}$$ is$$:\dfrac{\sqrt{7}}{\sqrt{3}}$$
Question 2
1 / -0

Aqueous solution of which of the following is green?

A
$$V^{2+}$$

B
$$V^{+3}$$

C
$$VO^{2+}$$

D
$$VO_{2}^{+}$$

Solution

$$V^{2+}\longrightarrow$$ Mauve/Lavender.
$$V^{3+}\longrightarrow$$ Green.
$$VO^{2+}\longrightarrow$$ Blue.
$$VO_2^{+}\longrightarrow$$ Yellow.
Question 3
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Which one of the following compound is both colored and paramagnetic?

A
$$ScCl_3$$

B
$$TiCl_4$$

C
$$CrCl_3$$

D
$$CuCl$$

Solution

The species which have unpaired electron in d-subshell is both paramagnetic and coloured.
$$Sc^{3+}\longrightarrow 4s^03d^0$$
$$Ti^{4+}\longrightarrow 4s^03d^0$$
$$Cr^{3+}\longrightarrow 4s^03d^3$$
$$Cu^{+}\longrightarrow 4s^03d^{10}$$
$$Cr^{3+}$$ is having $$3$$ unpaired $$e^-$$, thus paramagnetic and hence show color due to transition of these unpaired.
Question 4
1 / -0

In the dichromate di-anion:

A
4$$Cr-O$$ bonds are equivalent

B
6$$Cr-O$$ bonds are equivalent

C
all $$Cr-O$$ bonds are equivalent

D
all $$Cr-O$$ are non equivalent

Solution

The Dichromate di-anion consists of two tetrahedra sharing an oxygen at the common corner.The chromate ion has the tetahedral structure. The six terminal bond in the dichromate ion have same bond length due to resonance. Hence all six $$Cr-O$$ bonds are equal.
Question 5
1 / -0

Maximum ferromagnetism is found in ?

A
$$Fe$$

B
$$Ni$$

C
$$Co$$

D
$$None$$

Solution

As Iron have highest value of saturation, Magnetization $$M_s$$ which is defined as the magnetic moment density when the material is subjected to a field strong enough to align all its moments.
$$Fe \ 1707 \ M_s$$
$$Co \ 1400 \ M_s$$
$$Ni \ 485 \ M_s$$
Question 6
1 / -0

An aqueous solution containing $$V^{x+}$$ ion has magnetic moment equal to $$\sqrt {15} \ BM$$. Therefore, the x is:

A
$$5$$

B
$$2$$

C
$$3$$

D
$$4$$

Solution

Let $$n$$ be the number of unpaired electrons.
Magnetic moment $$= \sqrt {n(n+2)}= \sqrt {15}$$
$$\Rightarrow n=3$$
Atomic number of Vanadium is $$23$$. So, it must loose all its $$4s$$ electrons to get $$3$$ unpaired d electrons.
$$\therefore$$ value of $$x$$ will be $$2$$
Question 7
1 / -0

Which of the following is paramagnetic?

A
$$V(CO)_{6}$$

B
$$Fe(CO)_{5}$$

C
$$Fe_{2}(CO)_{9}$$

D
$$Cr(CO)_{6}$$

Solution

$${ V\left( CO \right) }_{ 6 }\Rightarrow V-23$$
$${ 1s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }{ 3s }^{ 2 }{ 3p }^{ 6 }{ 4s }^{ 2 }{ 3d }^{ 3 }$$
$$CO-$$weak ligand
$$\Rightarrow $$ para-magnetic in nature.
Question 8
1 / -0

Smallest ionic radius is:

A
$${La}^{3+}$$

B
$${U}^{3+}$$

C
$${Yb}^{3+}$$

D
$${Cf}^{3+}$$

Solution

Atomic and ionic radius of lanthanides decreases from La to Lu.
Due to the contraction of lanthanide the decrease in ionic radius of the element in the lanthanide series from lanthanum to lutetium occurs.
Question 9
1 / -0

Which of the following species do not exist?

A
$$PbF_4$$

B
$$PbCl_4$$

C
$$PbO_2$$

D
$$Pbl_4$$

Solution

$$PbF_4$$ exists but $$PbI_4$$ does not exist as $$I_2$$ reduces $$Pb(II)$$ to $$Pb$$ and oxidizes $$I$$ to $$I_2$$. Since, $$I_2$$ is not strong reducing agent to reduce $$Pb(II)$$ to $$Pb$$. Hence, $$PbI_2$$ is formed and not $$PbI_4$$.
Question 10
1 / -0

What would be magnetic moment of $$Gd^{+3}$$ ($$Z = 64$$)?

A
7.9 BM

B
3.62 BM

C
10.60 BM

D
9.72 BM

Solution

Electronic configuration of $$[Gd]^{3+}:[Xe]4f^{7}$$
Hence number of unpaired electron $$n=7$$
Hence, $$magnetic \ moment=\sqrt{n(n+2)}=\sqrt{63}=7.9BM$$

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Re-Attempt Weekly Quiz Competition

The d- and f- Block Elements Test - 40

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The d- and f- Block Elements Test - 40

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Question 1

$$7 : 3$$

$$3 : 7$$

$$\sqrt7 : \sqrt3$$

$$\sqrt3 : \sqrt7$$

Solution

Question 2

$$V^{2+}$$

$$V^{+3}$$

$$VO^{2+}$$

$$VO_{2}^{+}$$

Solution

Question 3

$$ScCl_3$$

$$TiCl_4$$

$$CrCl_3$$

$$CuCl$$

Solution

Question 4

4$$Cr-O$$ bonds are equivalent

6$$Cr-O$$ bonds are equivalent

all $$Cr-O$$ bonds are equivalent

all $$Cr-O$$ are non equivalent

Solution

Question 5

$$Fe$$

$$Ni$$

$$Co$$

$$None$$

Solution

Question 6

$$5$$

$$2$$

$$3$$

$$4$$

Solution

Question 7

$$V(CO)_{6}$$

$$Fe(CO)_{5}$$

$$Fe_{2}(CO)_{9}$$

$$Cr(CO)_{6}$$

Solution

Question 8

$${La}^{3+}$$

$${U}^{3+}$$

$${Yb}^{3+}$$

$${Cf}^{3+}$$

Solution

Question 9

$$PbF_4$$

$$PbCl_4$$

$$PbO_2$$

$$Pbl_4$$

Solution

Question 10

7.9 BM

3.62 BM

10.60 BM

9.72 BM

Solution

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