p-Block Elements

NEET Chemistry · 114 questions · Page 6 of 12 · Click an option or "Show Solution" to reveal answer

Q51

Which of the following statement is not correct about diborane?

A There are two 3-centre-2-eletron bonds.

B The four terminal B-H bonds are two centre two electron bonds.

C The four terminal Hydrogen atoms and the two Boron atoms lie in one plane.

D Both the Boron atoms are sp 2 hybridised.

Correct Answer

Option D

Solution

Each boron atoms in diborane uses sp 3 hybrid orbitals for bonding.

Q52

Noble gases are named because of their inertness towards reactivity. Identify an incorrect statement about them.

A Noble gases have large positive values of electron gain enthalpy

B Noble gases are sparingly soluble in water

C Noble gases have very high melting and boiling points

D Noble gases have weak dispersion forces

Correct Answer

Option C

Solution

Nobles gases have weak interatomic forces (van der Waals' forces). So, they have low melting and boiling points.

Q53

In which one of the following arrangements the given sequence is not strictly according to the properties indicted against it?

A CO 2 < SiO 2 < SnO 2 < PbO 2 : Increasing oxidizing order

B HF < HCl < HBr < HI : Increasing acidic strength

C H 2 O < H 2 S < H 2 Se < H 2 Te : Increasing pK a values

D NH 3 < PH 3 < AsH 3 < SbH 3 : Increasing acidic character

Correct Answer

Option C

Solution

Stronger is the acid, lower is the value of pK a .

On moving down the group, bond dissociation enthalpy of hydrides of group 16 elements decreases hence acidity increases and pK a value decreases.

Correct order of pK a value will be H 2 O > H 2 S > H 2 Se > H 2 Te

Q54

Which of the following is not correct about carbon monoxide?

A It reduces oxygen carrying ability of blood.

B The carboxyhemoglobin (haemoglobin bound to CO) is less stable than oxyhaemoglobin.

C It produced due to incomplete combustion.

D It forms carboxyhaemoglobin.

Correct Answer

Option B

Solution

The carboxyhaemoglobin is about 300 times more stable than oxyhaemoglobin.

Q55

Match the following and identify the correct option.<br><table> <thead> <tr> <td>

List - I		List - II
(A)	</td><td>CO(g) + H<sub>2</sub>(g)</td> <td>	(i)	</td><td>Mg(HCO<sub>3</sub>)<sub>2</sub> + Ca(HCO<sub>3</sub>)<sub>2</sub></td> </tr> </thead> <tbody> <tr> <td>
(B)	</td> <td>Temporary hardness of water</td> <td>	(ii)	</td> <td>An electron deficient hydride</td> </tr> <tr> <td>
(C)	</td> <td>B<sub>2</sub>H<sub>6</sub></td> <td>	(iii)	</td> <td>Synthesis gas</td> </tr> <tr> <td>
(D)	</td> <td>H<sub>2</sub>O<sub>2</sub></td> <td>	(iv)	</td> <td>Non-planar structure</td> </tr> </tbody> </table>

A <table> <thead> <tr> <th>(A)</th> <th>(B)</th> <th>(C)</th> <th>(D)</th> </tr> </thead> <tbody> <tr> <td>(iii)</td> <td>(ii)</td> <td>(i)</td> <td>(iv)</td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> </tbody> </table>

B <table> <thead> <tr> <th>(A)</th> <th>(B)</th> <th>(C)</th> <th>(D)</th> </tr> </thead> <tbody> <tr> <td>(iii)</td> <td>(iv)</td> <td>(ii)</td> <td>(i)</td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> </tbody> </table>

C <table> <thead> <tr> <th>(A)</th> <th>(B)</th> <th>(C)</th> <th>(D)</th> </tr> </thead> <tbody> <tr> <td>(i)</td> <td>(iii)</td> <td>(ii)</td> <td>(iv)</td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> </tbody> </table>

D <table> <thead> <tr> <th>(A)</th> <th>(B)</th> <th>(C)</th> <th>(D)</th> </tr> </thead> <tbody> <tr> <td>(iii)</td> <td>(i)</td> <td>(ii)</td> <td>(iv)</td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td></td> </tr> </tbody> </table>

Correct Answer

Option D

Solution

$\bullet$ Mixture of CO and H 2 gases is known as water gas or synthesis gas.

$\bullet$ Temporary hardness of water is due to bicarbonates of calcium and magnesium.

$\bullet$ Diborane (B 2 H 6 ) is an electron deficient hydride.

$\bullet$ H 2 O 2 is non-planar molecule having open book like structure.

Q56

Identify the correct statements from the following : (A) CO 2 (g) is used as refrigerant for ice-cream and frozen food. (B) The structure of C 60 contains twelve six-carbon rings and twenty five carbon rings. (C) ZSM-5, a type of zeolite, is used to convert alcohols into gasoline. (D) CO is colourless and odourless gas.

A (A) and (C) only

B (B) and (C) only

C (C) and (D) only

D (A), (B) and (C) only

Correct Answer

Option C

Solution

Dry ice is used as refrigerant.

C 60 contains 20 six membered ring, 12 five membered rings.

In the presence of a zeolite catalyst (HZSM-5), ethanol, methanol and larger alcohols can be converted into gasoline at 300-400

^\circ

C. CO, is a tasteless, colorless, and odorless gas.

Q57

Which of the following is incorrect statement?

A GeX 4 (X = F, Cl, Br, I) is more stable than GeX 2

B SnF 4 is ionic in nature

C PbF 4 is covalent in nature

D SiCl 4 is easily hydrolysed

Correct Answer

Option C

Solution

PbF 4 is an ionic compound.

Q58

Identify the incorrect statement related to PCl 5 from the following :

A Axial P–Cl bonds are longer than equatorial P–Cl bonds

B PCl 5 molecule is non-reactive

C Three equatorial P–Cl bonds make an angle of 120º with each other

D Two axial P–Cl bonds make an angle of 180º with each other

Correct Answer

Option B

Solution

Three equatorial bonds and two axial bonds. Due to unsymmetry PCl 5 is reactive.

Q59

Which is the correct thermal stability order for H 2 E (E = O, S, Se, Te and Po)?

A H 2 Po < H 2 Te < H 2 Se < H 2 S < H 2 O

B H 2 Se < H 2 Te < H 2 Po < H 2 O < H 2 S

C H 2 S < H 2 O < H 2 Se < H 2 Te < H 2 Po

D H 2 O < H 2 S < H 2 Se < H 2 Te < H 2 Po

Correct Answer

Option A

Solution

The thermal stability of hydrides decreases down the group due to decrease in bond dissociation energy down the group.

Therefore, thermal stability order will be : H 2 Po < H 2 Te < H 2 Se < H 2 S < H 2 O

Q60

Which of the following species is not stable?

A [Sn(OH) 6 ] 2-

B [SiCl 6 ] 2–

C [SiF 6 ] 2–

D [GeCl 6 ] 2–

Correct Answer

Option B

Solution

[SiCl 6 ] 2– does not exist because six large chloride ions cannot be accommodated around Si +4 due to its small size.

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