Practice Start Test

Chemical Bonding & Molecular Structure

NEET Chemistry · 95 questions · Page 8 of 10 · Click an option or "Show Solution" to reveal answer

Q71
Which of the following is not a correct statement?
A Multiple bonds are always shorter than corresponding single bonds.
B The electron-deficient molecules can act as Lewis acids.
C The canonical structures have no real existence.
D Every AB 5 molecule does in fact have square pyramid structure.
Correct Answer
Option D
Solution

AB 5 molecule has generally trigonal bipyramidal structure.

Sometimes due to presence of lone pair of electrons the structure gets distorted.

Q72
The electronegativity difference berween N and F is greater than that between N and H yet the dipole moment of NH 3 (1.5D) is larger than that of NF 3 (0.2 D). This is because
A in NH 3 the atomic dipole and bond dipole are in the opposite directions whereas in NF 3 these are in the same direction
B in NH 3 as well as in NF 3 the atomic dipole and bond dipole are in the same direction
C in NH 3 the atomic dipole and bond dipole are in the same direction whereas in NF 3 these are in opposite directions
D in NH 3 as well as in NF 3 the atomic dipole and bond dipole are in opposite directions.
Correct Answer
Option C
Solution

The dipole moment of NF 3 is 0.24 D and of NH 3 is 1.48 D.

In NF 3 , the dipole moment vector are aligned in opposite direction to that of the dipole moment vector of lone pair on N–atom which partly cancel out.

On the other hand, N–H bonds in NH 3 are in the same direction of dipole moment of the lone pair on N-atom which adds up the new resultant dipole moment.

Q73
Which of the following species has a linear shape?
A O 3
B NO 2 −-
C SO 2
D NO 2 +
Correct Answer
Option D
Solution

Due to sp hybridisation of N + , NO 2 + ion has linear shape.

Q74
The correct sequence of increasing covalent character is represented by
A LiCl < NaCl < BeCl 2
B BeCl 2 < LiCl < NaCl
C NaCl < LiCl < BeCl 2
D BeCl 2 < NaCl < LiCl
Correct Answer
Option C
Solution

As difference of electronegativity increases % iconic charecter increases and covalent charecter decreases i.e, electronegativity difference decreases covalent charecter increases.

Further greater the charge on the cation more will be its covalent character.

Be has maximum (+2) charge.

Q75
The surface tension of which of the following liquid is maximum ?
A C 2 H 5 OH
B CH 3 OH
C H 2 O
D C 6 H 6
Correct Answer
Option C
Solution

Hydrogen bonding in H 2 O > C 2 H 5 OH > CH 3 OH Hence, H 2 O has maximum surface tension.

Q76
The correct order in which the O −- O bond length increases in the following is
A O 2 < H 2 O 2 < O 3
B O 3 < H 2 O 2 < O 2
C H 2 O 2 < O 2 < O 3
D O 2 < O 3 < H 2 O 2
Correct Answer
Option D
Solution

Bond lengths of O −- O in O 2 is 1.21 Å, in H 2 O 2 is 1.48 Å and in O 3 is 1.28Å.

Therefore, correct order of the O −- O bond length is H 2 O 2 > O 3 > O 2 or O 2 < O 3 < H 2 O 2

Q77
Which of the following molecules has trigonal planar geometry?
A BF 3
B NH 3
C PCl 3
D IF 3
Correct Answer
Option A
Solution

IF 3 has three bond pairs and two lone pairs, thus, it has sp 3 d hybridization.

PCl 3 has three bond pairs and one lone pair thus, it has sp 3 hybridization.

NH 3 has three bond pairs and one lone pair thus, it has sp 3 hybridisation.

BF 3 has three bond pairs and no lone pair thus, it has sp 2 hybridisation.

Q78
H 2 O is dipolar, whereas BeF 2 is not. It is because
A the electronegativity of F is greater than that of O
B H 2 O involves hydrogen bonding whereas BeF 2 is a discrete molecule
C H 2 O is linear and BeF 2 is angular
D H 2 O is angular and BeF 2 is linear.
Correct Answer
Option D
Solution

In H 2 O the central atom oxygen has two lone pairs of electrons and two bond pairs of electrons.

Thus, the shape of H 2 O is bent or V-shape.

Thus, the two dipoles of H-O bonds have some resultant value as they are not exactly in the opposite direction to cancel out each other.

While in BeF 2 , there are two bond pairs on central atom Be, hence it is linear in shape.

Thus, the two dipoles of bonds are exactly in opposite direction to each other and cancel each other to give net zero dipole moment.

Q79
In BrF 3 molecule, the lone pairs occupy equatorial positions to minimize
A lone pair - bond pair repulsion only
B bond pair - bond pair repulsion only
C lone pair - lone pair repulsion and lone pair - bond pair repulsion
D lone pair - lone pair repulsion only.
Correct Answer
Option D
Solution

Lone pair - Lone pair repulsion > lone pair - bond pair repulsion > bond pair-bond pair repulsion.

The lone pairs of electrons are arranged on equatorial position as they are at maximum distance at these positions and hence they have minimum repulsion at these positions.

Q80
Among the following, the pair in which the two species are not isostructural is
A SiF 4 and SF 4
B IO 3 −- and XeO 3
C BH 4 −- and NH 4 +
D PF 6 −- and SF 6
Correct Answer
Option A
Solution

SiF 4 has symmetrical tetrahedral shape which is due to sp 3 hybridisation of the central silicon atom in its excited state configuration.

SF 4 has distorted tetrahedral or sea-saw geometry which arises due to sp 3 d hybridisation of the central sulphur atom and due to the presence of one lone pair of electrons in one of the equatorial hybrid orbital.

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