The p-Block Elements Test

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The p-Block Elements Test - 47

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Question 1
1 / -0

Ionisation enthalpy $$(\Delta _iH_1\ kJ \ mol^{-1})$$ for the elements of Group $$13$$ follows the order:

A
$$B > Al > Ga > In > Tl$$

B
$$B < Al > Ga < In > Tl$$

C
$$B < Al > Ga > In > Tl$$

D
$$B > Al < Ga > In < Tl$$

Solution

On moving down the group from $$B$$ to $$Tl$$, a regular decreasing trend in the I.E. is not observed.
Element $$B$$ $$Al$$ $$Ga$$ $$In$$ $$Tl$$
I.E. (kJ/mol) 801 577 579 558 589
In Ga, there are ten d-electrons in the penultimate shell which screen the nuclear charge less effectively and thus, outer electron is held firmly. As a result, the ionisation energy of both Al and Ga is nearly the same. The increase in ionisation energy from In to Tl is due to poor screening effect of 14f electrons present in the inner shell.
Thus, the correct order is, $$B>Al<Ga>In<Tl$$
Question 2
1 / -0

Which of the following is correct?

A
$$\%$$ abundance of $$B^{10}=$$% abundance of $$B^{11}$$

B
$$\%$$ abundance of $$B^{10}>$$% abundance of $$B^{11}$$

C
$$\%$$ abundance of $$B^{10}<$$% abundance of $$B^{11}$$

D
none of the above

Solution

.
Let the percentage existence of $$B10$$ isotope be $$x$$. Therefore percentage existence of the other isotope is $$(100-x)$$

mass of $$B-10$$ isotope is $$10amu$$
mass of $$B-11$$ isotope is $$11 amu$$

Therefore .
$$\dfrac{10x}{100+11(100-x)/100}=10.2$$

$$10x+11(100-x)=1020$$
$$1100-x=1020$$

$$x=80$$

Therefore the percentage of Boron-10 isotope is $$80$$%
and Boron-11 isotope is$$(100-x)=20$$%
Hence option B is the correct answer
Question 3
1 / -0

Which among $${ CH }_{ 4 }, { SiH }_{ 4 }, { GeH }_{ 4 }, { SnH }_{ 4 }$$ is the most volatile?

A
$${ CH }_{ 4 }$$

B
$${ SiH }_{ 4 }$$

C
$${ GeH }_{ 4 }$$

D
$${ SnH }_{ 4 }$$

Solution

$$ CH_4 $$ is most volatile among all because methane has a very low molecular weight of 16. So as the molecular weight increases, the vander waals forces of attraction between the molecules also increases.
Question 4
1 / -0

Borax, disodium tetraborate is an a important boron compound, a mineral, and a salt of boric acid. The number of terminal $$B-----OH$$ presents in borax is ?

A
$$3$$

B
$$4$$

C
$$5$$

D
$$6$$

Solution

The figure shows there are 4 $$B-OH$$ bonds present in Borax.
Question 5
1 / -0

Which of the following statements is correct?

A
$$BCl_3$$ and $$AlCl_3$$ are both Lewis acids and $$BCl_3$$ is stronger acid than $$AlCl_3$$

B
$$BCl_3$$ and $$AlCl_3$$ both Lewis acids and $$AlCl_3$$ is stronger acid than $$BCl_3$$

C
$$BCl_3$$ and $$AlCl_3$$ are both equally strong Lewis acids

D
Both $$BCl_3$$ and $$AlCl_3$$ are not Lewis acids
Solution
Both $$BCl_3$$ and $$AlCl_3$$ are Lewis acids.
$$BCl_3$$ is a stronger Lewis acid as the bond formed with the base will involve 2p orbital overlap which is stronger than the 3p orbital overlap in the case of $$AlCl_3$$. Hence, the bond formed between $$BCl_3$$ and the Lewis base will be stronger.
Question 6
1 / -0

Which of the following statements is correct with respect to the property of elements with increase in atomic number in the carbon family (group 14)?

A
Their metallic character decreases.

B
The stability of +2 oxidation state increases.

C
Their ionization energy increases.

D
Their atomic size decreases.
Solution
- In group-14 the general oxidation states shown by the elements are +4,+2. The stability of +2 oxidation state increases down the group because of inert pair effect.
- The reason for this is the pairing energy of the s-orbital electrons is more than the energy released during the bond formation.
Question 7
1 / -0

Moissan boron is_____

A
Amorphous boron of ultra purity

B
Crystalline boron of ultra purity

C
Amorphous boron of low purity

D
Crystalline boron of low purity

Solution

The Moissan boron is the amorphous boron of low purity. It is 95-98% pure.
It is generally black in colour due to the contamination by metal borides. It is obtained by the reduction of boric anhydride.
Question 8
1 / -0

Four hydrogenation reactions maximum catalytic activity is shown by:

A
Group $$5-11$$ elements

B
Group $$5-9$$ elements

C
Group $$7-9$$ elements

D
Group $$9-11$$ elements
Solution
- To treat or combine chemically an unsaturated compound with hydrogen. Liquid vegetable oils are often hydrogenated to turn them into solids. To turn coal into oil by combining its carbon with hydrogen to form hydrocarbons.
- In periodic table Group 7-9 elements show maximum catalytic activity in Hydrogenation reactions.
Question 9
1 / -0

Which of the following statement is incorrect?

A
The hydroxide of aluminium is more acidic than that of boron

B
The hydroxide of boron is basic whereas that of aluminium is amphoteric

C
The hydroxide of boron is acidic whereas that of aluminium is amphoteric

D
The hydroxide of both boron and aluminium are amphoteric
Solution
- Boron forms just covalent compounds while aluminium forms even some ionic compounds.
- The oxides and hydroxides of boron are acidic in nature. As compared to this, the oxides and hydroxides of aluminium are amphoteric in nature.
Question 10
1 / -0

$$CO_2$$ is a gas, while $$SiO_2$$ is a solid but both are:

A
covalent containing $$\pi$$ -bond

B
molecules having $$p\pi $$ - $$ d\pi $$ bonding

C
acidic

D
discrete molecules
Solution
- $$CO_2$$ consists of individual molecules with one central carbon atom double bonded to two oxygen atoms. Silicon does not form double bonds with oxygen. $$CO_2$$ is gas but $$SiO_2$$ is solid because the $$SiO_2$$ is in giant molecular structure but the $$CO_2$$ is simple molecular structure.because of this reason $$CO_2$$ is gas but $$SiO_2$$ is solid.
- $$CO_2$$ is an acidic oxide can be explained by Lux-Flood concept & extended Lewis theory. $$CO_2$$ with $$H_2O$$ produces $$H_2CO_3$$ i.e. carbonic acid.
- Silicon dioxide has no basic properties - it doesn't contain oxide ions and it doesn't react with acids. Instead, it is very weakly acidic, reacting with strong bases. Silicon dioxide doesn't react with water, because of the difficulty of breaking up the giant covalent structure.

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Element	$$B$$	$$Al$$	$$Ga$$	$$In$$	$$Tl$$
I.E. (kJ/mol)	801	577	579	558	589

The p-Block Elements Test - 47

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The p-Block Elements Test - 47

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Question 1

$$B > Al > Ga > In > Tl$$

$$B < Al > Ga < In > Tl$$

$$B < Al > Ga > In > Tl$$

$$B > Al < Ga > In < Tl$$

Solution

Question 2

$$\%$$ abundance of $$B^{10}=$$% abundance of $$B^{11}$$

$$\%$$ abundance of $$B^{10}>$$% abundance of $$B^{11}$$

$$\%$$ abundance of $$B^{10}<$$% abundance of $$B^{11}$$

none of the above

Solution

Question 3

$${ CH }_{ 4 }$$

$${ SiH }_{ 4 }$$

$${ GeH }_{ 4 }$$

$${ SnH }_{ 4 }$$

Solution

Question 4

$$3$$

$$4$$

$$5$$

$$6$$

Solution

Question 5

$$BCl_3$$ and $$AlCl_3$$ are both Lewis acids and $$BCl_3$$ is stronger acid than $$AlCl_3$$

$$BCl_3$$ and $$AlCl_3$$ both Lewis acids and $$AlCl_3$$ is stronger acid than $$BCl_3$$

$$BCl_3$$ and $$AlCl_3$$ are both equally strong Lewis acids

Both $$BCl_3$$ and $$AlCl_3$$ are not Lewis acids

Solution

Question 6

Their metallic character decreases.

The stability of +2 oxidation state increases.

Their ionization energy increases.

Their atomic size decreases.

Solution

Question 7

Amorphous boron of ultra purity

Crystalline boron of ultra purity

Amorphous boron of low purity

Crystalline boron of low purity

Solution

Question 8

Group $$5-11$$ elements

Group $$5-9$$ elements

Group $$7-9$$ elements

Group $$9-11$$ elements

Solution

Question 9

The hydroxide of aluminium is more acidic than that of boron

The hydroxide of boron is basic whereas that of aluminium is amphoteric

The hydroxide of boron is acidic whereas that of aluminium is amphoteric

The hydroxide of both boron and aluminium are amphoteric

Solution

Question 10

covalent containing $$\pi$$ -bond

molecules having $$p\pi $$ - $$ d\pi $$ bonding

acidic

discrete molecules

Solution

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