The d- and f- Block Elements Test

Result

The d- and f- Block Elements Test - 42

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Weekly Quiz Competition

Question 1
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Which of the following can convert acidified $${ Cr }_{ 2 }{ O }_{ 7 }{^{2-}}$$ to green product?

A
$${ SO }_{ 2 },{ H }_{ 2 }{ SO }_{ 3 }$$ and $${ H }_{ 2 }{ SO }_{ 4 }$$

B
$${ SO }_{ 2 },{ H }_{ 2 }{ S }_{ }$$ and $${ H }_{ 2 }{ SO }_{ 3 }$$

C
$${ SO }_{ 3 },{ H }_{ 2 }{ S }$$ and $${ Fe }^{ 3+ }$$

D
$${ SO }_{ 3 }^{ - },{ H }_{ 2 }S$$ and $${ Fe }^{ +2 }$$

Solution

Experimental verification for the presence of sulphur dioxide $$\left( { SO }_{ 2 } \right) $$ gas
$${ K }_{ 2 }{ Cr }_{ 2 }{ O }_{ 7 }+{ H }_{ 2 }{ SO }_{ 4 }+3{ SO }_{ 2 }\rightarrow { K }_{ 2 }{ SO }_{ 4 }+{ Cr }_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 }+{ H }_{ 2 }O$$
Orange-coloured-dichromate solution turns green due to formation of chromium (III) sulphate.
Question 2
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The pair having similar magnetic moment is:

A
$$Ti^{3+},V^{3+}$$

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

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

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

Solution
Question 3
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Which of the following ions have zero value of magnetic moment?

A
$$Sc^{3+}$$

B
$$Ti^{4+}$$

C
$$Zn^{2+}$$

D
None of these

Solution

It's because $$Sc^{3+}$$ does not have any electrons left in its d orbital. Sc has theelectron configuration $$[Ar](4s)^2(3d)^1$$ but in order to get its +3 oxidation state, it has to lose 3 electrons, starting with the two 4s electrons and followed by the lone 3d electron.
Hence n=0 which makes magnetic moment zero.
Question 4
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The ratio of spin only magnetic moment of $$Fe^{3+}$$ and $$CO^{2+}$$ is:

A
$$\sqrt { 24 } : \sqrt { 15 }$$

B
$$7 : 3$$

C
$$\sqrt { 35 } : \sqrt { 15 } $$

D
$$\sqrt { 5 } : \sqrt { 7 }$$

Solution
Question 5
1 / -0

Number of identical Cr-O bonds in dichromate ion $$Cr_2O_7^{2-}$$ is :

A
4

B
6

C
7

D
8

Solution

The correct answer is - There are '6' identical Cr - O bonds in the dichromate ion $$(Cr_2O_7^{-2}).$$

In a dichromate ion $$(Cr_2O_7^{-2}).$$, there are 6 terminal Cr – O bonds. All these bonds are equivalent due to resonance.

The Dichromate ions $$(Cr_2O_7^{-2}).$$ are oxoanions of chromium in the oxidation state +6.
Hence option B is correct answer.
Question 6
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Green $$Cr^{3+}$$ changes to yellow $${ CrO }_{ 4 }^{ 2- }$$ on boiling with

A
Alkaline $$H_2O_2$$

B
Acidified for $$H_2O_2$$

C
Both (1) and (2)

D
None of these
Question 7
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In the dichromate anion $$\left( { Cr }_{ 2 }{ O }_{ 7 }^{ -2 } \right) $$:

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

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

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

D
No bonds in $${ Cr }_{ 2 }{ O }_{ 7 }^{ -2 }$$ are equivalent
Question 8
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Actinoids belongs to following type of elements:

A
s -block element

B
d -block element

C
f -block element

D
p -block element

Solution

The two rows that are generally placed underneath the main Periodic Table are called the lanthanide series and the actinide series.

These two rows are produced when electrons are being added to f orbitals.
Therefore, this block of elements are referred to as the "f block".
Question 9
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Figure

A
Ethane

B
Propane

C
n- Butane

D
n-pentane

Solution
Question 10
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Magnetic moment of $${X^{3 + }}$$ion od $$3d$$ series is $$\sqrt {35} \,BM$$. What is atomic number of $${X^{3 + }}$$?

A
$$25$$

B
$$26$$

C
$$27$$

D
$$28$$

Solution