Hydrogen bonds are formed in many compounds e.g., $\mathrm{H}_{2} \mathrm{O}, \mathrm{HF}, \mathrm{N

Question

Hydrogen bonds are formed in many compounds e.g., $\mathrm{H}_{2} \mathrm{O}, \mathrm{HF}, \mathrm{NH}_{3}$. 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\

Professor PC Thomas Classes · Answer

(b): Strength of H -bonding depends on the electronegativity of the atom which follows the order : $\mathrm{F}>\mathrm{O}>\mathrm{N}$\ ∴ Strength of H -bond is in the order :\ $H \cdots \cdots F>H \cdots \cdots O>H \cdots \cdots N$\ But each $\mathrm{H}_{2} \mathrm{O}$ molecule is linked to 4 other $\mathrm{H}_{2} \mathrm{O}$ molecules through H -bonds whereas each HF molecule is linked only to two other HF molecules.\ Hence, correct decreasing order of the boiling points is $\mathrm{H}_{2} \mathrm{O}>\mathrm{HF}>\mathrm{NH}_{3}$.