Chemical Bonding & Molecular Structure — Page 6 | NEET Chemistry

Q51

The pair of species with the same bond order is

A O

_2^{2 - }

, B 2

B O

_2^{ + }

, NO +

C NO, CO

D N 2 , O 2

Correct Answer

Option A

Solution

O 2 - $\to$ 1 B 2 $\to$ 1 O 2 + $\to$ 2.5 NO + $\to$ 3 NO $\to$ 2.5 CO $\to$ 3 N 2 $\to$ 3 O 2 $\to$ 2

Q52

Which one of the following pairs is isostructural (i.e., having the same shape and hybridization) ?

A [BCl 3 and BrCl 3 ]

B [NH 3 and NO

_3^ -

]

C [NF 3 and BF 3 ]

D [BF

_4^ -

and NH

_4^ +

]

Correct Answer

Option D

Solution

BCl 3 $\Rightarrow$ sp 2 , trigonal planar BrCl 3 $\Rightarrow$ sp 3 d, T-shaped NH 3 $\Rightarrow$ sp 3 , pyramidal NO 3 - $\Rightarrow$ sp 2 , trigonal planar NF 3 $\Rightarrow$ sp 3 , pyramidal BF 3 $\Rightarrow$ sp 2 , trigonal planar BF 4 - $\Rightarrow$ sp 3 , tetrahedral NH 4 - $\Rightarrow$ sp 3 , tetrahedral

Q53

Bond order of 1.5 is shown by

A O 2 +

B O 2

-

C O 2 2

-

D O 2

Correct Answer

Option B

Solution

Configuration of O 2

\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^2{\pi ^*}2p_x^1{\pi ^*}2p_y^1

Bond order =

{{No.\,of\,{e^ - }\,in\,bonding\,M.O - No.\,of\,{e^ - }\,in\,antibonding\,M.O} \over 2}

Bond order of O 2 + =

{{10 - 5} \over 2}

= 2.5 Bond order of O 2 - =

{{10 - 7} \over 2}

= 1.5 Bond order of O 2 2- =

{{10 - 8} \over 2}

= 1 Bond order of O 2 =

{{10 - 6} \over 2}

= 2

Q54

The pairs of species of oxygen and their magnetic behaviours are noted below. Which of the following presents the correct description?

A

O_2^ - ,O_2^{2 - }

- Both diamagnetic

B

O_2^ + ,{O_2}

- Both paramagnetic

C O,

O_{2}^{2-}

- Both paramagnetic

D

{O^ + },O_2^{2 - }

- Both paramagnetic

Correct Answer

Option B

Solution

O 2 + = KKσ2s 2 σ*2s 2 σ2p z 2 (π2p x 2 = π2p y 2 ) (π*2p x 1 ) O 2 = KKσ2s 2 σ*2s 2 σ2p z 2 (π2p x 2 = π2p y 2 ) (π*2p x 1 = π*2p y 1 ) O 2 and O 2 + contain unpaired electron in π* ABMO so paramagnetic.

Q55

The correct order of increasing bond length of C

-

H, C

-

O, C

-

C and C

=

C is

A C

-

H < C

=

C < C

-

O < C

-

C

B C

-

C < C

=

C < C

-

O < C

-

H

C C

-

O < C

-

H < C

-

C < C

=

C

D C

-

H < C

-

O < C

-

C < C

=

C

Correct Answer

Option A

Solution

Increasing order of bond length is

\mathop {C - H}\limits_{107\,pm} < \mathop {C = C}\limits_{134\,pm} < \mathop {C - O}\limits_{141\,pm} < \mathop {C - C}\limits_{134\,pm}

Q56

The pairs of species of oxygen and their magnetic behavior are noted below. Which of the following presents the correct description?

A O

_2^ -

, O

_2^{2 - }

- Both diamagnetic

B O + , O

_2^{2 - }

- Both paramagnetic

C O

_2^{ + }

, O 2 - Both paramagnetic

D O, O

_2^{2 - }

- Both paramagnetic

Correct Answer

Option C

Solution

O_2^+

and

O_2

are paramagnetic in nature as they contain one and two unpaired electrons respectively.

Q57

Which of the following has the minimum bond length ?

A O 2 +

B O 2

-

C O 2 2

-

D O 2

Correct Answer

Option A

Solution

Electronic configuration O 2 :

\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^2{\pi ^*}2p_y^1{\pi ^*}2p_z^1

Bond order =

{1 \over 2}\left( {8 - 4} \right)

= 2 O 2 + : Bond order =

{1 \over 2}\left( {8 - 3} \right)

= 2.5 O 2 - : Bond order =

{1 \over 2}\left( {8 - 5} \right)

= 1.5 O 2 2- : Bond order =

{1 \over 2}\left( {8 - 6} \right)

= 1 As bond order increases, bond length decreases.

Q58

Some of the properties of the two species,

NO_3^ -

and

{H_3}{O^ + }

are described below. Which one of them is current?

A Dissimilar in hybridization for the central atom with different structures.

B Isostructural with same hybridization for the central atom.

C Isostructural with different hybridization for the central atom

D Similar in hybridization for the central atom with different structures.

Correct Answer

Option A

Solution

No. of electron pairs = No. of atoms bonded to it + 1/2[Gp. no. of central atom - Valency of central atom $\pm$ No. of electrons] For NO 3 - = 3 + 1/2[5 - 6 + 1] = 3 (sp 2 hybridisation) For H 3 O + = 3 + 1/2[6 - 3 - 1] = 4 (sp 3 hybridisation)

Q59

In which of the following molecules the central atom does not have sp 3 hybridization?

A CH 4

B SF 4

C BF 4

-

D NH 4 +

Correct Answer

Option B

Solution

For neutral molecules No. of electron pairs = No. of atoms bonded to it + 1/2[Gp. no. of central atom - Valency of central atom] $\therefore$ For CH 4 , no. of e - pairs = 4 + 1/2[4 - 4] = 4 (sp 3 hybridisation) For SF 4 , no. of e - pairs = 4 + 1/2[6 - 4] = 5 (sp 3 d hybridisation) and For ions, No. of electron pairs = No. of atoms bonded to it + 1/2[Gp. no. of central atom - Valency of central atom $\pm$ No. of electrons] $\therefore$ For BF 4 - , no. of e - pairs = 4 + 1/2[3 - 4 + 1] = 4 (sp 3 hybridisation) For NH 4 + , no. of e - pairs = 4 + 1/2[5 - 4 - 1] = 4 (sp 3 hybridisation)

Q60

In which of the following pairs of molecules/ ions, the central atoms have sp 2 hybridisation ?

A NO

_2^{ - }

and NH 3

B BF 3 and NO

_2^{ - }

C NH

_2^{ - }

and H 2 O

D BF 3 and NH

_2^{ - }

Correct Answer

Option B

Solution

The hybridisation of the central atom can be calculated as H =

{1 \over 2}\left[ \begin{array}{ll}\left( \begin{array}{ll}No.\,of\,electrons \\ in\,valence\,shell \\ of\,atom \end{array} \right) + \left( \begin{array}{ll}No.\,of\,monovalent \\ atoms\,around \\ central\,atom \end{array} \right) \\ - \left( \begin{array}{ll}Ch{\mathop{\rm arge}\nolimits} \,on \\ cation \end{array} \right) + \left( \begin{array}{ll}Ch{\mathop{\rm arge}\nolimits} \,on \\ anion \end{array} \right) \end{array} \right]

$\therefore$ For BF 3 , H =

{1 \over 2}\left[ {(3) + (3) - (0) + (0)} \right] \Rightarrow 3 \Rightarrow

sp 2 hybridisation $\therefore$ For NO 2 - , H =

{1 \over 2}\left[ {(5) + (0) - (0) + (1)} \right] \Rightarrow 3 \Rightarrow

sp 2 hybridisation