Question

The most volatile liquid among the following is:
(A) Ether
(B) Liquid nitrogen
(C) Liquid helium
(D) Liquid neon

Answer 1

Hint: To answer this question, you should recall the concept of Intermolecular forces. They are the attractive and repulsive forces that arise between the molecules of a substance. These forces mediate the interactions between individual molecules of a substance

Complete step by step solution:
Intermolecular forces refer to the attractive and repulsive forces that arise between the molecules due to interaction. The boiling point of molecules depends on the intermolecular force of attraction, stronger the force, higher is the boiling point. Dipole-dipole interactions are attractive forces among polar molecules. This type of interaction is shown by ether.
While liquid neon and helium show London dispersion forces arise due to the interactions between an instantaneous dipole and an atom/molecule. As helium has the smallest atomic weight hence has the weakest London dispersion force. Liquid Helium is the most volatile liquid which is evident by the value of heat of evaporation: $ 0.083kJ/mol $ which is very less. Therefore, we can conclude that the correct answer to this question is option C.

Note:
You should know about the other types of Intermolecular forces
Ion-Dipole Interactions: These interactions arise between ions and polar molecules. The strength of this interaction is proportional to the magnitude of the dipole moment, size disparity and charge disparity of an ion
Ion Induced Dipole Interactions: A non-polar molecule is polarized by an ion placed near it due to induction. Now after this polarization, both behave as induced dipoles.
Dipole Induced Dipole Interaction: Non-polar molecules are transformed into induced dipoles due to the presence of a polar molecule nearby.
Dispersion Forces or London Forces: Arises due to the movement of electrons thus creating temporary positive and negative charged regions.