Question

The sublimation of iodine is due to:
A.Low melting point
B.WeaK I-I BOND
C.Weak van der waals force among I2 molecules.
D.Lone pair lone pair repulsion in I2 molecule

Answer 1

There are various phase transitions.Sublimation is the conversion of solid into gaseous form. When a solid changes into a gas force of attraction among the molecule decreases.

Complete step by step answer:
Sublimation is one of the phase changes from solid to gas state. We know that in a solid substance the constituent particles will be closely packed and they are held together by strong forces. When they change from solid to liquid these forces become weak so the distance between the particles increases. In the gas state the constituent particles are more free to move and there will be a very weak force of attraction between the molecules.
Iodine is a crystalline substance. When it is heated it will change to a gas state. Actually, it does not pass through a liquid phase. The sublimation of iodine occurs in presence of air or ${O_2}$ . Because of the large size of iodine, it has a low melting point. But it is not responsible for its sublimation. For sublimation to occur the constituent particles should be able to overcome the force of attraction among them.
In iodine weak Vander waals forces are present. Because of these weak forces when it is heated the molecule can easily break and can go to the gaseous state.
Hence the correct answer is C.

Note: Vander waals forces are attractive or cohesive intermolecular forces. It is of various types. These are dipole-dipole forces or keelson forces, dipole induced dipole forces or Debye force and induced dipole-induced dipole forces or dispersion force. This dispersion force is also known as London forces. These weak attractive forces constitute the major factor contributing to the force that exists in noble gases. When iodine is heated it changes to purple vapours.