Why AIF₃ is a high melting solid whereas SiF₄ is a gas?

1

(a)

AIF₃ is an ionic compound whereas SiF₄ is a non-polar covalent compound. Hence, interparticle forces in AIF₃  are much stronger that's why it is a high melting solid.

What type of  atomic orbitals  can overlap to form molecular orbitals?

1

(a)

Atomic orbitals  with comparable energies and proper orientation overlap to form molecular orbitals

What is valence bond approach for the formation of covalent bond?

1

(a)

A covalent bond is formed by the overlap of half-filled atomic orbitals.

Why axial bonds of PCI₅ are longer than equatorial bonds?

1

(a)

This is due to greater repulsion on the axial bond pairs by the equatorial bond pairs of electrons.

Why is the energy of  \({ \pi 2p }_{ x }\) and  \({ { \pi 2p } }_{ y }\) molecular orbital lower than \({ \sigma 2p }_{ z }\) molecular orbital in \({ N }_{ 2 }\) molecule?

1

(a)

This is because of intermixing of 2s and \({ 2p }_{ z }\) orbitals because of their close proximity. Due to intermixing, \({ \sigma 2p }_{ z }\) molecular orbital becomes higher in energy than \({ \pi 2p }_{ x }\) and \({ { \pi 2p } }_{ y }\) molecular orbitals.

Why NF₃ is pyramidal but BF₃ is triangular planar?

1

(a)

In NF₃, N is surrounded by three F atoms and a lone pair thus, have lp-bp repulsion along with bp-bp repulsion.
Thus, its shape is pyramidal.
In BF₃, B is surrounded by only three F atoms, i.e. have no lone pairs, so only repulsion present in it is bp - bp.
Thus, its shape is triangular planar.

Predict the geometry of XeF₄ molecule.

1

(a)

XeF₄ = 4bp + 2lp (This is because Xe contains 8 valunce electrons) = square planar geometry.

Explain why HF is less viscous than H₂O

2

(a)

Explain the shape of BrF₅

2

(a)

What is the total number of sigma and pi bond in the following molecules?

2

(a)

Which of the species have similar shape and why? \({ { NO }_{ 2 }^{ - } },{ { NO }_{ 2 }^{ + } },{ CO }_{ 2 },{ O }_{ 3 }\)

2

(a)

Explain why PCl₅ is trigonal bipyramidal,whereas IF ₅ is square pyramidal?

2

(a)

Define electronegativity. How does it differ from electron gain enthalpy ?

3

(a)

Draw the shape of the following hybrid orbitals sp, sp² and sp³.

3

(a)

Draw the structure of CuSO₄.5H₂O. Also, name the type of bond present in it.

3

(a)

What is the type of hybridisation of carbon atoms marked with star?

5

(a)

Represent diagrammatically the bond moments and the resultant dipole moment in CO₂, NF and CHCL₃.

5

(a)

Which hybrid orbitals are used by carbon atoms in the following molecules?
(a) CH₃–CH₃;
(b) CH₃–CH=CH₂;
(c) CH₃-CH₂-OH;
(d) CH₃-CHO
(e) CH₃COOH

5

(a)