The p-Block Elements Test

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The p-Block Elements Test - 30

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Weekly Quiz Competition

Question 1
1 / -0

Crystalline boron in small amounts may be obtained by :

A
Reducing $$BCl_3$$ with $$H_2$$

B
pyrolysis of $$BI_3$$

C
thermal decomposition of diborane

D
all of these

Solution

Crystalline boron is obtained by reducing volatile boron halides with hydrogen at high temperatures. Ultrapure boron for use in semiconductor industry is produced by the decomposition of diborane at high temperature and then purified with the zone melting process.
Question 2
1 / -0

The type of glass used in making lenses and prisms is :

A
A flint glass

B
Jena glass

C
Pyrex glass

D
Quartz glass

Solution

Flint glass is used in opticals and prisms. Flint glass is optical glass that has a relatively high refractive index and low Abbe number. A concave lens of flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet lens because of their compensating optical properties, which reduces chromatic aberration.
Hence option A is correct.
Question 3
1 / -0

The number of possible isomers for disubstituted borazine,$$B_3 N_3 H_4 X_2$$ is:

A
3

B
4

C
6

D
2

Solution

The number of possible isomers of distributed borazine is 4 because of 4 reactive hydrogen ions.
Question 4
1 / -0

Which of the following pair consists of only network solid?

A
$$ SiO_2, CO_2 $$

B
Graphite, $$ SO_2 $$

C
$$ P_4O_{10}, P_4O_6 $$

D
Diamond , $$ SiO_2 $$
Solution
1. A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule.
2. So in Diamond , $$SiO_2$$ atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule.
3. Hence option D is correct.
Question 5
1 / -0

From the $$B_2 H_6$$, all the following can be prepared except:

A
$$H_3 BO_3$$

B
$$[BH_2(NH_3)_2]^{+} [BH_4]^{-}$$

C
$$B_2(CH_3)_6$$

D
$$NaBH_4$$

Solution

$${ B }_{ 2 }{ H }_{ 6 }+6{ H }_{ 2 }O\rightarrow 2B\left( OH \right) _{ 3 }+6{ H }_{ 2 }\\ { B }_{ 2 }{ H }_{ 6 }+2N{ H }_{ 3 }\rightarrow [{ BH }_{ 2 }\left( { NH }_{ 3 } \right) _{ 2 }]^{ + }[{ BH }_{ 4 }]^{ - }\\ { 2B }_{ 2 }{ H }_{ 6 }+2Na\rightarrow { NaBH }_{ 4 }+Na{ B }_{ 3 }{ H }_{ 8 }$$
Question 6
1 / -0

Amorphous boron of 95% to 98% purity is obtained by:

A
heating $$B_2 O_3$$ with $$H_2$$

B
heating $$B_2O_3$$ with $$Mg$$ or $$Na$$ at high temperature

C
heating $$KBF_4$$ with $$Na$$ or $$K$$

D
heating $$BBr_3$$ with $$H_2$$ in presence of a catalyst

Solution

Amorphous boron is a brown powder which is not the pure form of boron. It is obtained by reduction of boric oxide with metals such as magnesium or aluminium and the product is contaminated with metal borides.
Question 7
1 / -0

Boron of highest purity (99.9%) is obtained by:

A
reduction of $$B_2 O_3$$ by $$Mg$$

B
electrolysis of fused tetrafluoroborates $$(KBF_4)$$ in molten $$KF$$

C
reduction of $$BCl_3$$ with $$H_2$$ at 1270 $$K$$

D
thermal decomposition of boranes at 1173 $$K$$

Solution

The elemental boron was obtained by reduction of boron oxides with metals such as magnesium and aluminium but boron obtained is not pure. Pure boron(99.9%) can be prepared by reducing volatile boron halides with hydrogen at high temperature.
Question 8
1 / -0

What does P, Q & R represent in the given figure of nitrogen cycle ?

A
P Ammonia Q Nitrates R Nitrites

B
P Ammonia Q Nitrites R Nitrates

C
P Nitrites Q Nitrates R Ammonia

D
P Nitrates Q Nitrites R Ammonia

Solution
Question 9
1 / -0

Statement -1 : $$PbO_2$$ is an oxidising agent and reduced to PbO.
Statement - 2 : Stability of Pb (II) > Pb (IV) on account of inert pair effect.

A
Statement - l is True, Statement - 2 is True; Statement - 2 is a correct explanation for Stetement - l.

B
Statement - 1 is True. Statement - 2 is True; Statement - 2 is NOT a correct explanation for Statement - l

C
Statement - l is True, Statement - 2 is False

D
Statement - l is False, Statement - 2 is True

Solution

Statement -1 : $$PbO_2$$ is an oxidising agent and reduced to $$PbO$$.

$$Pb(IV)$$ in $$PbO_2$$ gains electrons to form $$Pb(II)$$ in $$PbO$$. Hence it is an oxidizing agent

Statement - 2 : Stability of $$Pb (II) > Pb (IV)$$ on account of the inert pair effect.

The inert pair effect is the tendency of the electrons in the outermost atomic s-orbital to remain un-ionized or unshared in compounds of post-transition metals. That is the reason $$PbO_2$$ acts as an oxidising agent and readily reduces to $$PbO$$.
Question 10
1 / -0

Amorphous boron on burning in air forms :

A
$$B(OH)_3$$

B
mixture of $$B_2O_3$$ and $$BN$$

C
only $$B_2O_3$$

D
only $$BN$$

Solution

Amorphous boron on burning in the air gives a mixture of boron trioxide and boron nitride. Boron burns with a brilliant flame in oxygen.
The reaction can be given as follow:
$$ 4B + 3O_{2} \rightarrow 2B_{2}O_{3}$$
$$ 2B + N_{2} \rightarrow 2BN$$

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Re-Attempt Weekly Quiz Competition

The p-Block Elements Test - 30

Result

The p-Block Elements Test - 30

Score

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SHARING IS CARING

Question 1

Reducing $$BCl_3$$ with $$H_2$$

pyrolysis of $$BI_3$$

thermal decomposition of diborane

all of these

Solution

Question 2

A flint glass

Jena glass

Pyrex glass

Quartz glass

Solution

Question 3

3

4

6

2

Solution

Question 4

$$ SiO_2, CO_2 $$

Graphite, $$ SO_2 $$

$$ P_4O_{10}, P_4O_6 $$

Diamond , $$ SiO_2 $$

Solution

Question 5

$$H_3 BO_3$$

$$[BH_2(NH_3)_2]^{+} [BH_4]^{-}$$

$$B_2(CH_3)_6$$

$$NaBH_4$$

Solution

Question 6

heating $$B_2 O_3$$ with $$H_2$$

heating $$B_2O_3$$ with $$Mg$$ or $$Na$$ at high temperature

heating $$KBF_4$$ with $$Na$$ or $$K$$

heating $$BBr_3$$ with $$H_2$$ in presence of a catalyst

Solution

Question 7

reduction of $$B_2 O_3$$ by $$Mg$$

electrolysis of fused tetrafluoroborates $$(KBF_4)$$ in molten $$KF$$

reduction of $$BCl_3$$ with $$H_2$$ at 1270 $$K$$

thermal decomposition of boranes at 1173 $$K$$

Solution

Question 8

P Ammonia Q Nitrates R Nitrites

P Ammonia Q Nitrites R Nitrates

P Nitrites Q Nitrates R Ammonia

P Nitrates Q Nitrites R Ammonia

Solution

Question 9

Statement - l is True, Statement - 2 is True; Statement - 2 is a correct explanation for Stetement - l.

Statement - 1 is True. Statement - 2 is True; Statement - 2 is NOT a correct explanation for Statement - l

Statement - l is True, Statement - 2 is False

Statement - l is False, Statement - 2 is True

Solution

Question 10

$$B(OH)_3$$

mixture of $$B_2O_3$$ and $$BN$$

only $$B_2O_3$$

only $$BN$$

Solution

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