[BrF4]− has sp3d2 hybridization.Bromine has 7 valence electrons, plus 1 for the negative charge, giving 8. Four are used in bonds to F, leaving two lone pairs. With four bonding pairs and two lone pairs, there are six electron pairs around Br, arranged octahedrally (sp3d2). The two lone pairs occupy trans positions, so the ion is square planar, like XeF4, with which it is isoelectronic.SF4 has five electron pairs (one lone pair), sp3d, and a see-saw shape, so (A) and (B) describe a different electron count. sp3 would allow only four electron pairs.

Molecular Structure and Bonding Theory Questions and Answers

Q: The molecules P4 and CH4 exhibit the same :

P4 and CH4 share the same Geometry: both are tetrahedral.In white phosphorus the four P atoms sit at the corners of a tetrahedron, each bonded to the other three (P-P-P angles of 60°). In methane the four H atoms sit at the corners of a tetrahedron around carbon (H-C-H angles of 109.5°). The arrangements differ in detail, but both molecules have tetrahedral shape.They do not share the other properties. White phosphorus is a pale yellow waxy solid at 300 K with a boiling point near 280 °C, while methane is a colourless gas boiling at about -162 °C.

Q: The correct order of dipole moment for the following compounds is :

The order is (I) \(\lt\) (IV) \(\lt\) (III) \(\lt\) (II): toluene \(\lt\) 4-methylphenol \(\lt\) nitrobenzene \(\lt\) 4-nitrotoluene.Toluene has a small moment (about 0.4 D) from the weakly donating methyl group. 4-Methylphenol (p-cresol) is around 1.5 D, dominated by the OH dipole. Nitrobenzene is strongly polar (about 4.0 D) because the nitro group withdraws electrons from the ring.In 4-nitrotoluene the electron-donating methyl and electron-withdrawing nitro group are para to each other, so their moments point the same way along the axis and add, giving about 4.4 D, the largest of the four. Orders placing nitrobenzene or 4-nitrotoluene low ignore the size of the nitro dipole.

Q: Which of the following has the weakest binding ?

The weakest binding is van der Waals forces.Van der Waals forces are weak, short-range attractions between molecules arising from temporary or permanent dipoles, typically under 10 kJ/mol. They are intermolecular forces, not true chemical bonds.Covalent, coordinate and ionic bonds are true chemical bonds with energies of the order of hundreds of kJ/mol, tens of times stronger.

Q: [NO2]+ has a shape similar to :

\([\text{NO}_{2}]^{+}\) has a shape similar to \(\text{SiO}_{2}\), taken as the linear O=Si=O unit.The nitronium ion is isoelectronic with CO2: nitrogen has two double bonds to oxygen and no lone pair, so it is linear (sp, AX2). A monomeric SiO2 unit, with silicon in the same group as carbon, would likewise be linear. (Solid silica is a network of SiO4 tetrahedra, but the question compares the triatomic formula.)SO2 and O3 have a lone pair on the central atom (AX2E) and are bent at about 119° and 117°; water has two lone pairs and is bent at 104.5°. None of them is linear.

61.

The molecules P₄ and CH₄ exhibit the same :

A.Color
B.Geometry
C.Boiling point
D.Physical state at 300 K

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: B

P₄ and CH₄ share the same Geometry: both are tetrahedral.

In white phosphorus the four P atoms sit at the corners of a tetrahedron, each bonded to the other three (P-P-P angles of 60°). In methane the four H atoms sit at the corners of a tetrahedron around carbon (H-C-H angles of 109.5°). The arrangements differ in detail, but both molecules have tetrahedral shape.

They do not share the other properties. White phosphorus is a pale yellow waxy solid at 300 K with a boiling point near 280 °C, while methane is a colourless gas boiling at about -162 °C.

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62.

The correct order of dipole moment for the following compounds is :

Four benzene derivatives labelled I to IV: toluene (I), 4-nitrotoluene (II), nitrobenzene (III) and 4-methylphenol (IV)

A.(III) \(\lt\) (I) \(\lt\) (IV) \(\lt\) (II)
B.(III) \(\lt\) (II) \(\lt\) (I) \(\lt\) (IV)
C.(I) \(\lt\) (IV) \(\lt\) (III) \(\lt\) (II)
D.(I) \(\lt\) (II) \(\lt\) (III) \(\lt\) (IV)

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: C

The order is (I) \(\lt\) (IV) \(\lt\) (III) \(\lt\) (II): toluene \(\lt\) 4-methylphenol \(\lt\) nitrobenzene \(\lt\) 4-nitrotoluene.

Toluene has a small moment (about 0.4 D) from the weakly donating methyl group. 4-Methylphenol (p-cresol) is around 1.5 D, dominated by the OH dipole. Nitrobenzene is strongly polar (about 4.0 D) because the nitro group withdraws electrons from the ring.

In 4-nitrotoluene the electron-donating methyl and electron-withdrawing nitro group are para to each other, so their moments point the same way along the axis and add, giving about 4.4 D, the largest of the four. Orders placing nitrobenzene or 4-nitrotoluene low ignore the size of the nitro dipole.

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63.

[BrF₄]⁻ has :

A.Shape similar to \(\mathrm{SF}_{4}\)
B.\(sp^{3}d\) hybridization
C.\(sp^{3}\) hybridization
D.\(sp^{3}d^{2}\) hybridization

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: D

[BrF₄]⁻ has sp³d² hybridization.

Bromine has 7 valence electrons, plus 1 for the negative charge, giving 8. Four are used in bonds to F, leaving two lone pairs. With four bonding pairs and two lone pairs, there are six electron pairs around Br, arranged octahedrally (sp³d²). The two lone pairs occupy trans positions, so the ion is square planar, like XeF₄, with which it is isoelectronic.

SF₄ has five electron pairs (one lone pair), sp³d, and a see-saw shape, so (A) and (B) describe a different electron count. sp³ would allow only four electron pairs.

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64.

Which of the following has the weakest binding ?

A.Covalent bond
B.Coordinate bond
C.Ionic bond
D.van der Waals forces

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: D

The weakest binding is van der Waals forces.

Van der Waals forces are weak, short-range attractions between molecules arising from temporary or permanent dipoles, typically under 10 kJ/mol. They are intermolecular forces, not true chemical bonds.

Covalent, coordinate and ionic bonds are true chemical bonds with energies of the order of hundreds of kJ/mol, tens of times stronger.

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65.

[NO₂]⁺ has a shape similar to :

A.\(\text{SO}_{2}\)
B.\(\text{SiO}_{2}\)
C.\(\text{H}_{2}\text{O}\)
D.\(\text{O}_{3}\)

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: B

\([\text{NO}_{2}]^{+}\) has a shape similar to \(\text{SiO}_{2}\), taken as the linear O=Si=O unit.

The nitronium ion is isoelectronic with CO₂: nitrogen has two double bonds to oxygen and no lone pair, so it is linear (sp, AX₂). A monomeric SiO₂ unit, with silicon in the same group as carbon, would likewise be linear. (Solid silica is a network of SiO₄ tetrahedra, but the question compares the triatomic formula.)

SO₂ and O₃ have a lone pair on the central atom (AX₂E) and are bent at about 119° and 117°; water has two lone pairs and is bent at 104.5°. None of them is linear.

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66.

Hardness of diamond is due to

A.Coordinate bonding
B.Covalent bonding
C.Electrovalent bonding
D.van der Waals forces

Exam Year(s)

UGC NET - 2012,

Answer: B

The hardness of diamond is due to covalent bonding, option B. Each carbon atom is bonded to four others by strong covalent bonds in a continuous three-dimensional network, so that there are no weak planes in the crystal, and a great deal of energy is needed to break it.

Coordinate bonding (option A) is a covalent bond in which one atom donates both electrons and is not the bond in diamond. Electrovalent bonding (option C) is ionic and needs two different elements. Van der Waals forces (option D) are the weak forces between the layers of graphite, which makes graphite soft. The contrast with graphite is the usual way this question is set.

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