The p-Block Elements Test

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The p-Block Elements Test - 41

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Question 1
1 / -0

What is hybridisation of boron in $$[B(OH)_4]^-$$?

A
$$sp^2$$

B
$$sp^3$$

C
$$sp^3d^2$$

D
None of these

Solution

Hybridisation of boron in $$[B(OH)_4]^{-}$$ is $$sp^{3}$$
Hybridisation is $$sp^{3}$$ (Refer to Image 1)

electronic configuration of boron $$\longrightarrow1s^{2}2s^{2}2p^1$$
(Refer to Image 2)

electronic configuration of boron in first excited state
(Refer to Image 3)

Boron forms $$4sp^3$$ hybrid orbitals
The unpaired orbitals forms covalent bond with $$3-OH$$ groups
The empty orbital forms co-ordinate covalent with $$-OH^{-}$$ group
The boron atom in $$B(OH)_3 $$ is electron deficient: it has 6 rather than 8 electrons in its valence shell. It acts as a Lewis acid by readily accepting the lone pair from the oxygen in a water molecule to go from sp2 to sp3 hybridisation.
Question 2
1 / -0

Which of the following statement is correct with respect to the property of elements in carbon family?With an increase in their atomic number their:

A
atomic size decreases

B
ionization energy increases

C
metallic character decreases

D
stability of $$+2$$ oxidation state increases

Solution

As the atomic number of the element increases the stability of the compounds in +2 oxidation state increases down the group due to inert pair effect.
Hence option $$D$$ is correct.
Question 3
1 / -0

Metals react with silicons to form:

A
silicates

B
silanes

C
silicides

D
mixture of silicates and silanes
Question 4
1 / -0

Which of the following oxide is formed by carbon?

A
Sesquioxide

B
Suboxide

C
Superoxide

D
All

Solution

Carbon suboxide $$O = C = C = C = O$$
Question 5
1 / -0

Boron nitride has the structure of the type:

A
Graphite type

B
Diamond type

C
Both diamond and graphite type

D
$$NaCl$$ type

Solution

Hexagonal boron nitride $$(h-BN)$$ is the equivalent in the structure of graphite.

Like graphite, its plate-like microstructure and layered lattice structure give it good lubricating properties.

Hence, option $$A$$ is correct.
Question 6
1 / -0

The only hydride formed by lead has the formula:

A
$$PbH_2$$

B
$$PbH_4$$

C
$$PbH_6$$

D
$$PbH_3$$

Solution

A hydride is the anion of hydrogen, $$H^{ - }$$, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, the hydrogen atom is bonded to a more electropositive element or group. Compounds containing hydrogen bonded to metals or metalloid may also be referred to as hydrides. Almost all of the elements form binary compounds with hydrogen, the exceptions being $$He, Ne, Ar, Kr, Pm, Os, Ir, Rn, Fr,$$ and $$Ra$$

Plumbane, $${ PbH }_{ 4 }$$, is a metal hydride and group 14 hydride composed of lead and hydrogen.
$$\left[ 1 \right] $$ Plumbane is not well characterized or well known, and it is thermodynamically unstable with respect to the loss of a hydrogen atom.
$$\left[ 2 \right] $$ Derivatives of plumbane include lead tetrafluoride, ($${ PbF }_{ 4 }$$), and tetraethyllead, $$\left( { \left( { CH }_{ 3 }{ CH }_{ 2 } \right) }_{ 4 }Pb \right) $$
Question 7
1 / -0

The naturally occuring radioactive isotope of carbon is:

A
$$C-12$$

B
$$C-13$$

C
$$C-14$$

D
none of the above

Solution

The longest-lived radioisotope is $$^{14}C$$ , with a half life of 5,700 years.
Question 8
1 / -0

Addition of mineral acid to an aqueous solution of Borax, the compound formed is:

A
Puroboric acid

B
Boron hydride

C
Meta boric acid

D
Orthoboric acid
Solution
Correct Option: $$D$$

Hint: The chemical formula of Borax is $$Na_2B_4O_7$$.

Explanation:
- When a solution of Borax reacts with a mineral acid such as $$HCl$$ orthoboric acid is formed.
- The reaction is as shown below;
$$Na_2B_4O_7+5H_2O+2HCl\rightarrow 4H_3BO_3+2NaCl$$
- Orthoboric acid is a weak, monobasic acid of boron.
Question 9
1 / -0

Physical properties of a substance are given.
P $$\rightarrow$$ It is colour less
Q $$\rightarrow$$ has intense smell
R $$\rightarrow$$ It's aqueous solution possesses basic property.
Which of the above physical properties are correct for sulphur dioxide?

A
Only $$P$$ and $$Q$$

B
$$P, Q$$ and $$R$$

C
Only $$Q$$ and $$R$$

D
Only $$R$$

Solution

Sulphur dioxide is a colorless gas and it has an intense smell.
Question 10
1 / -0

Which of the following is not silicate?

A
Zeolite

B
Feldspar

C
Ultramarine

D
Silica

Solution

Except silica, all the other three are silicates.

Zeolite $$-\ Na_2Al_2Si_2O_8\cdot xH_2O$$

Feldspar $$-\ KAlSi_3O_8$$,

Ultramarine $$-\ Na_8(AlO_2)_6 \cdot (SiO_2)_6S_2$$

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Re-Attempt Weekly Quiz Competition

The p-Block Elements Test - 41

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The p-Block Elements Test - 41

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Question 1

$$sp^2$$

$$sp^3$$

$$sp^3d^2$$

None of these

Solution

Question 2

atomic size decreases

ionization energy increases

metallic character decreases

stability of $$+2$$ oxidation state increases

Solution

Question 3

silicates

silanes

silicides

mixture of silicates and silanes

Question 4

Sesquioxide

Suboxide

Superoxide

All

Solution

Question 5

Graphite type

Diamond type

Both diamond and graphite type

$$NaCl$$ type

Solution

Question 6

$$PbH_2$$

$$PbH_4$$

$$PbH_6$$

$$PbH_3$$

Solution

Question 7

$$C-12$$

$$C-13$$

$$C-14$$

none of the above

Solution

Question 8

Puroboric acid

Boron hydride

Meta boric acid

Orthoboric acid

Solution

Question 9

Only $$P$$ and $$Q$$

$$P, Q$$ and $$R$$

Only $$Q$$ and $$R$$

Only $$R$$

Solution

Question 10

Zeolite

Feldspar

Ultramarine

Silica

Solution

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