Hydrogen bond | Applications of hydrogen bonds

The electrostatic force of attraction present between the more electronegative atom of one molecule and the partially positively charged hydrogen atom of another molecule is called hydrogen bonding.

Hydrogen bonding is only present with fluorine, oxygen, nitrogen and rarely with chlorine.

Applications of hydrogen bonding

Thermodynamic properties

Hydrogen fluoride is a weaker acid than Hydrochloric acid. Why?

In hydrogen fluoride, molecules are present in a zigzag manner. One hydrogen atom is entrapped between two fluorine atoms and it is not easy to remove hydrogen atoms from hydrogen fluoride molecules. 

Water molecules have higher boiling points than hydrogen fluoride and Azane. Why? 

In water molecules, two hydrogen atoms are present. So it forms two hydrogen bonds per molecule.

In hydrogen fluoride molecules, only one hydrogen is present and farms only one hydrogen bond per molecule. Therefore, boiling point of water is higher than hydrogen fluoride. 

Covalent hydrides of Group four have a lower boiling point than the other covalent hydrides. Why?

Electronegativity of the elements of group 4A and lower than the other groups like Group fiveA, sixA and sevenA. So covalent hydrides of Group 4 have no intermolecular forces than the other covalent hydrides. Due to which boiling points of covalent hydrides of Group 4A is less than the other covalent hydrides.

Water is liquid, but hydrogen sulfide is gas at room temperature. Why? 

In water molecules, strong hydrogen bonding is present between the water molecules. Due to which water is liquid at room temperature.

Hydrogen sulfide has weak intermolecular forces between the molecules due to which hydrogen sulfide is gas at room temperature.

Boiling point of hydrogen chloride is higher than hydrochloric acid. Why?

In hydrogen fluoride molecules, strong hydrogen bonding is present between the hydrogen fluoride molecules and boiling point of hydrogen fluoride molecules is higher than hydrochloric acid.

In hydrochloric acid molecules, hydrogen bonding is not present but dipole dipole forces are present which are weaker than hydrogen bonding. Due to which hydrochloric acid has a lower boiling point than hydrogen fluoride.