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Relationship between Intermolecular Forces and Structural Features

The nature and magnitude/strength of intermolecular forces depends on the type of bonds and other structural features of the molecules. For example, both NH3 and PH3 have same number of bonds and same molecular shape.

However, there is a vast difference in their boiling points. For example, boiling point of NH3 is greater than that of PH3. It means that intermolecular forces operating in liquid ammonia and in liquid PH3 have different strength. Similarly, H2S and H20 are both triatomic molecules and possess bent Shape along with two lone pairs. But H2S is gas at room temperature whereas H20 is liquid. It also means that intermolecular forces in H2O(l) are relatively much stronger than those in H2S

The magnitude of interparticle forces also differ in H2O, NH3, PH3 and H2S because each one will have different boiling point. Thus, we conclude that nature and magnitude of intermolecular forces depend upon, the molecular shape and type of bonds it contains.

EFFECT OF INTERMOLECUL AR FORCES ON THE OPERTIES OF MOLECUL AR SUBSTANCES

The magnitude of interparticle forces control many of physical properties such as melting point, boiling point, the physical , surface tension, molar heat of vaporisation, extent of evaporation, etc. In many cases they also affect the chemical properties of the substances. It may be noted that the chemical properties are mostly controlled by intramolecular forces which exists within the same molecule.