Hydrogen bonds are formed in many compounds e.g., H₂O, HF, NH₃ . The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :
A. HF > H₂ O > NH₃

B. H₂O > HF > NH₃

C. NH₃ > HF > H₂ O

D. NH₃ > H₂O > HF

The strength of H-bonding depends on the electronegativity of the atom which follows the order: F > O > N.
Thus, the strength of bonding will be in the following order:
H……. F > H…….O > H…….. N
The H₂O molecule is linked to 4 other H₂O molecules through H-bonds whereas each HF molecule is linked only to two other HF molecules.

Thus, the H₂O molecules bonding will be stronger than HF bonding.

Hence, correct decreasing order of the boiling points is H₂O > HF > NH₃