Question

Why does ${\mathrm{NH}}_3$ have a lower boiling point than ${\mathrm{H}}_2\mathrm{O}$?

Answer 1

Boiling point:-

• The boiling point is defined as the temperature at which boiling starts for any compound and at that temperature vapour pressure of the compound becomes equal to the atmospheric pressure.
• The boiling point depends on the two major factors type or strength of the bonding and the surface area of the compound.

Boiling point Comparison of ${\mathrm{NH}}_3\left(\mathrm{ammonia}\right)$ and ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{Water}\right)$

• Both the compounds is having hydrogen bonding in the molecule.
• Hydrogen bonding is the interaction between more electronegative elements and Hydrogen.
• Nitrogen is less electronegative than Oxygen and so a less strong Hydrogen bond will form in this case of ${\mathrm{NH}}_3$.
• Hence, ${\mathrm{NH}}_3$ have lower boiling point than ${\mathrm{H}}_2\mathrm{O}$.