Chemical Bonding & Molecular Structure — Page 9 | JEE Chemistry

Q81

Arrange the following in increasing order of their covalent character. A.

\mathrm{CaF}_{2}

B.

\mathrm{CaCl}_{2}

C.

\mathrm{CaBr}_{2}

D.

\mathrm{CaI}_{2}

Choose the correct answer from the options given below.

A B < A < C < D

B A < B < C < D

C A < B < D < C

D A < C < B < D

Correct Answer

Option B

Solution

From Fajan's rule, for a given metal ion, as the size of anion increases, polarizability of anion increases and hence covalent character of the given ionic compound increases.

Hence, the increasing order of covalent character is $\mathrm{CaF}_{2}<\mathrm{CaCl}_{2}<\mathrm{CaBr}_{2}<\mathrm{Cal}_{2}$

Q82

Given below are two statements. Statement I:

\mathrm{O}_{2}, \mathrm{Cu}^{2+}

, and

\mathrm{Fe}^{3+}

are weakly attracted by magnetic field and are magnetized in the same direction as magnetic field. Statement II:

\mathrm{NaCl}

and

\mathrm{H}_{2} \mathrm{O}

are weakly magnetized in opposite direction to magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below.

A Both Statement I and Statement II are correct.

B Both Statement I and Statement II are incorrect.

C Statement I is correct but Statement II is incorrect.

D Statement I is incorrect but Statement II is correct.

Correct Answer

Option A

Solution

$\mathrm{O}_{2}, \mathrm{Cu}^{2+}$ and $\mathrm{Fe}^{3+}$ have 2,1 and 5 unpaired electrons respectively, so these are the paramagnetic species.

Hence, they are attracted by magnetic field. $\mathrm{NaCl}$ and $\mathrm{H}_{2} \mathrm{O}$ are the diamagnetic species so they are repelled by the magnetic field.

Q83

Which of the following pair of molecules contain odd electron molecule and an expanded octet molecule?

A

\mathrm{BCl}_{3}

and

\mathrm{SF}_{6}

B

\mathrm{NO}

and

\mathrm{H}_{2} \mathrm{SO}_{4}

C

\mathrm{SF}_{6}

and

\mathrm{H}_{2} \mathrm{SO}_{4}

D

\mathrm{BCl}_{3}

and

\mathrm{NO}

Correct Answer

Option B

Solution

(A) $\mathrm{BCl}_{3}$ - Even electron molecules $\mathrm{SF}_{6}$ - Expended octet molecules (B) $\mathrm{NO}$ - Odd electron molecules $\mathrm{H}_{2} \mathrm{SO}_{4}$ - Expanded octet (C) $\mathrm{SF}_{6}-$ Even electron molecules $\mathrm{H}_{2} \mathrm{SO}_{4}$ - Expanded octet (D) $\mathrm{BCl}_{3}-$ Even electron molecules $\mathrm{NO}$ - odd electron molecules

Q84

Number of lone pairs of electrons in the central atom of

\mathrm{SCl}_{2}, \mathrm{O}_{3}, \mathrm{ClF}_{3}

and

\mathrm{SF}_{6}

, respectively, are :

A 0, 1, 2 and 2

B 2, 1, 2 and 0

C 1, 2, 2 and 0

D 2, 1, 0 and 2

Correct Answer

Option B

Solution

The number of lone pair of electrons in the central atom of $\mathrm{SCl}_{2}, \mathrm{O}_{3}, \mathrm{ClF}_{3}$ and $\mathrm{SF}_{6}$ are 2, 1, 2 and $\mathrm{0}$ respectively Their structures are as,

Q85

For

\mathrm{OF}_{2}

molecule consider the following : A. Number of lone pairs on oxygen is 2 . B. FOF angle is less than

104.5^{\circ}

. C. Oxidation state of

\mathrm{O}

is

-2

. D. Molecule is bent '

\mathrm{V}

' shaped. E. Molecular geometry is linear. correct options are:

A A, C, D only

B A, B, D only

C C, D, E only

D B, E, A only

Correct Answer

Option B

Solution

A : No. of lone pairs on oxygen = 2 B : ( $\theta$ < Bond angle in H

_2

O (104.5

^\circ

) D : molecule is bent "v" shaped

Q86

The compound which does not exist is

A (NH

_4

)

_2

BeF

_4

B PbEt

_4

C BeH

_2

D NaO

_2

Correct Answer

Option D

Solution

Sodium superoxide (NaO $_2$ ) is not a stable compound. It is not found in normal conditions due to its high reactivity.

Q87

The magnetic behaviour of

\mathrm{Li_2O,Na_2O_2}

and

\mathrm{KO_2}

, respectively, are :

A paramagnetic, paramagnetic and diamagnetic

B paramagnetic, diamagnetic and paramagnetic

C diamagnetic, paramagnetic and diamagnetic

D diamagnetic, diamagnetic and paramagnetic

Correct Answer

Option D

Solution

$\mathrm{Li}_{2} \mathrm{O} \rightarrow \mathrm{O}^{2-} \rightarrow$ diamagnetic $\mathrm{Na}_{2} \mathrm{O}_{2} \rightarrow \mathrm{O}_{2}^{2-} \rightarrow$ diamagnetic $\mathrm{KO}_{2} \rightarrow \mathrm{O}_{2}^{-} \rightarrow$ paramagnetic

Q88

The bond dissociation energy is highest for

A Cl

_2

B I

_2

C Br

_2

D F

_2

Correct Answer

Option A

Solution

Bond energy of $\mathrm{F}_{2}$ less than $\mathrm{Cl}_{2}$ due to lone pair lone pair repulsions.

Bond energy order $\mathrm{Cl}_{2}>\mathrm{Br}_{2}>\mathrm{F}_{2}>\mathrm{I}_{2}$

Q89

Statement I : Dipole moment is a vector quantity and by convention it is depicted by a small arrow with tail on the negative centre and head pointing towards the positive centre. Statement II : The crossed arrow of the dipole moment symbolizes the direction of the shift of charges in the molecules. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is correct but Statement II is incorrect

B Statement I is incorrect but Statement II is correct

C Both Statement I and Statement II are correct

D Both Statement I and Statement II are incorrect

Correct Answer

Option B

Solution

The dipole moment is a vector quantity and is depicted by an arrow with tail on the positive centre and head pointing towards the negative centre.

So, Statement-I is incorrect.

The crossed arrow of the dipole moment symbolizes the direction of the shift of charges in the molecules.

So, Statement-II is correct.

For example,

Q90

Decreasing order of the hydrogen bonding in following forms of water is correctly represented by A. Liquid water B. Ice C. Impure water Choose the correct answer from the options given below :

A A = B > C

B B > A > C

C A > B > C

D C > B > A

Correct Answer

Option B

Solution

Extent of hydrogen bonding : Ice $>$ liquid water $>$ impure water - In ice, 4 molecules of $\mathrm{H}_{2} \mathrm{O}$ are connected to $\mathrm{H}_{2} \mathrm{O}$ molecule. - Impure water will have less hydrogen bonding.