The d- and f- Block Elements Test

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The d- and f- Block Elements Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

Magnetic moment $$\sqrt{35}$$ is true for which of the following pair :

A
$$Co^{+2}, Fe^{+2}$$

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

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

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

Solution

Magnetic moment = $$\sqrt{35}$$

$$\sqrt{n(n+2)}= 35$$

Therefore, n= 5

$$Fe^{3+}, Mn^{2+}- [Ar]3d^5$$
Question 2
1 / -0

The adsorption of hydrogen by platinum black is called :

A
hydrogenation

B
Reduction

C
Occlusion

D
Hydration

Solution

When adsorption happens on metals, it is called occlusion. Occlusion happens on a variety of metals, including iron, platinum and palladium, but hydrogen gas is the only adsorbate.
Question 3
1 / -0

Which pair of ions is colourless.

A
$$Mn^{+3}, CO^{+3}$$

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

C
$$Zn^{2+}, Sc^{3+}$$

D
$$Ti^{2+}, Cu^{2+}$$

Solution

As both $$Zn^{2+} = d^{10}, Sc^{3+} = d^0$$ have zero unpaired d-electron so they both are colourless.
Question 4
1 / -0

In the following electronic configuration $$\displaystyle ns^{2}\left ( n-1 \right )d^{0-1}\left ( n-2 \right )f^{1-14}$$. If value of $$\displaystyle \left ( n-1 \right )=6$$ the configuration will be of:

A
lanthanides

B
d - block

C
actinides

D
s - block

Solution

In the following electronic configuration $$\displaystyle ns^{2}\left (
n-1 \right )d^{0-1}\left ( n-2 \right )f^{1-14}$$ If value of $$\displaystyle \left ( n-1 \right )=6$$ the configuration will be of
Actinides.
$$\displaystyle n-1 = 6 $$ then $$\displaystyle n=7 $$ and $$\displaystyle n-2 = 5 $$. The electronic configuration will be $$\displaystyle 7s^{2}6d^{0-1}5f^{1-14}$$ which is characteristic of actinides.
Question 5
1 / -0

Which of the following is ferromagnetic.

A
Cu, Ag, Au

B
Fe, Co, Ni

C
Zn, Cd, Hg

D
Ca, Sr, Ba

Solution

Explanation:

Ferromagnetic substances are those which get strongly magnetized in the presence of a magnetic field.

These substances have domains that get aligned in the magnetic field, thus increasing their strength.

These are strongly attracted by a magnet.

Examples include $$iron, cobalt, nickel, etc.$$

Hence, option B is the correct answer.
Question 6
1 / -0

The magnetism of $$Ni^{2+}$$ ion is:

A
$$\cfrac {eh}{4\pi m}$$

B
$$ \sqrt 6 \left (\cfrac {eh}{4\pi m} \right )$$

C
$$ \sqrt 8 \left (\cfrac {eh}{4\pi m} \right )$$

D
$$ \sqrt {10} \left (\cfrac {eh}{4\pi m} \right )$$

Solution

$$Ni^{2+}$$ has valence shell electronic configuration of $$3d^84s^0$$. It contains 2 unpaired electrons. Its magnetic moment is given by:

$$ \displaystyle \sqrt {n(n+2)} \left (\cfrac {eh}{4\pi m} \right ) $$

$$= \sqrt {2(2+2)} \left (\cfrac {eh}{4\pi m} \right ) $$

$$= \sqrt 8 \left (\cfrac {eh}{4\pi m} \right )$$
Question 7
1 / -0

The incorrect statement in respect of chromyl chloride test is?

A
Formation of red vapour

B
Formation of leas chromate

C
Formation of carbonyl chloride

D
Liberation of chlorine

Solution

Hint: chromyl chloride test refers to a chemical test for the detection of chloride ions qualitatively.

Chromyl chloride test is a qualitative analysis test used for the conformation for $$\mathrm{Cl}^{-}$$ions.
Let us understand the reaction involved

Step 1: Take a small amount of soluble chloride salt with an equal amount of powdered $$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$$.

Step 2: Heat the mixture with conc. $$\mathrm{H}_{2} \mathrm{SO}_{4}$$.

$$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+4 \mathrm{KCl}+6 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow 2 \mathrm{CrO}_{2} \mathrm{Cl}_{2}+6 \mathrm{KHSO}_{4}+3 \mathrm{H}_{2} \mathrm{O}$$

Step 3: The orange red vapours of formed chromyl chloride
$$\left(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\right)$$ is passed through the $$\mathrm{NaOH}$$ solution taken in another test tube.
$$\mathrm{CrO}_{2} \mathrm{Cl}_{2}+4 \mathrm{NaOH} \rightarrow 2 \mathrm{Na}_{2} \mathrm{CrO}_{4}+2 \mathrm{NaCl}+2 \mathrm{H}_{2} \mathrm{O}$$

Step 4: The solution turns yellow.

Step 5: Add acetic acid to the solution and then lead acetate solution.
$$\mathrm{Na}_{2} \mathrm{CrO}_{4}+\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2} \mathrm{~Pb} \rightarrow \mathrm{PbCrO}_{4}+2 \mathrm{CH}_{3} \mathrm{COONa}$$

Step 6: Yellow PPT $$\left(P b C r O_{4}\right)$$ is formed.
So, from the above information, we can see there is no liberation of chlorine.

Final Answer:
Hence D is correct.
Question 8
1 / -0

Out of the ions $$Ag^+, Co^{2+}, Ti^{4+}$$, which one will be coloured in aqueous solutions.

[Atomic no : Ag = 47, Co = 27, Ti = 22]

A
$$Ag^+$$

B
$$Co^{2+}$$

C
$$Ti^{4+}$$

D
None of these

Solution

compound with unpaired d-electron will show color.

$$Ag^+ = 5d^{10} \,\,\,\,\,\,,n = 0$$

$$Ti^{+4} = 3s^2 3p^6 \,\,\,\,\,\,, n = 0$$

$$Co^{+2} = [Ar]3d^7\,\,\,\,\,\,\,,n = 3$$ It will show color due to unpaired d electrons.
Question 9
1 / -0

One unpaired electron in atom contributes a magnetic moment of 1.1 BM. The magnetic moment of $$Cr$$ (Atomic number 24) is:

A
4.6

B
5.6

C
6.6

D
7.6

Solution

$$Cr\left( z=24 \right) \Rightarrow \left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 6 }{ 4s }^{ 1 }{ 3d }^{ 5 }$$
$$n=6$$
Now, $$\mu =\sqrt { n\left( n+2 \right) } $$
$$\mu =\sqrt { 6\left( 8 \right) } =\sqrt { 48 } =6.6BM$$
Question 10
1 / -0

The ion that gives colourless compound:

A
$$Sc^{+3}$$

B
$$V^{+3}$$

C
$$Cr^{+3}$$

D
All of these

Solution

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The d- and f- Block Elements Test - 28

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The d- and f- Block Elements Test - 28

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Question 1

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

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

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

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

Solution

Question 2

hydrogenation

Reduction

Occlusion

Hydration

Solution

Question 3

$$Mn^{+3}, CO^{+3}$$

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

$$Zn^{2+}, Sc^{3+}$$

$$Ti^{2+}, Cu^{2+}$$

Solution

Question 4

lanthanides

d - block

actinides

s - block

Solution

Question 5

Cu, Ag, Au

Fe, Co, Ni

Zn, Cd, Hg

Ca, Sr, Ba

Solution

Question 6

$$\cfrac {eh}{4\pi m}$$

$$ \sqrt 6 \left (\cfrac {eh}{4\pi m} \right )$$

$$ \sqrt 8 \left (\cfrac {eh}{4\pi m} \right )$$

$$ \sqrt {10} \left (\cfrac {eh}{4\pi m} \right )$$

Solution

Question 7

Formation of red vapour

Formation of leas chromate

Formation of carbonyl chloride

Liberation of chlorine

Solution

Question 8

$$Ag^+$$

$$Co^{2+}$$

$$Ti^{4+}$$

None of these

Solution

Question 9

4.6

5.6

6.6

7.6

Solution

Question 10

$$Sc^{+3}$$

$$V^{+3}$$

$$Cr^{+3}$$

All of these

Solution

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