Liquid with a lower vapor pressure has a higher boiling point. Explain this
phenomenon in term of the relationship between vapor pressure and
intermolecular forces.

Question

Liquid with a lower vapor pressure has a higher boiling point. Explain this phenomenon in term of the relationship between vapor pressure and intermolecular forces.

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- **Definition of Vapor Pressure and Boiling Point**

- The vapor pressure of a liquid is the pressure exerted by its vapor when the liquid and vapor are in equilibrium.
  - The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure, i.e., $$ P_{	ext{vapor}} = P_{	ext{atmosphere}} $$.

- **Intermolecular Forces and Their Effect**

- Intermolecular forces (such as hydrogen bonding, dipole-dipole interactions, and London dispersion forces) hold the molecules of a liquid together.
  - When these forces are strong, molecules require more energy (higher temperature) to overcome them and escape into the vapor phase.
  - Consequently, liquids with strong intermolecular forces have a lower tendency to vaporize. This results in a lower vapor pressure at a given temperature.

- **Relationship Between Vapor Pressure and Boiling Point**

- A liquid with a lower vapor pressure has stronger intermolecular forces because fewer molecules can escape into the gas phase at any given temperature.
  - To reach the condition $$ P_{	ext{vapor}} = P_{	ext{atmosphere}} $$, a higher temperature is required to supply enough energy to overcome the intermolecular attractions.
  - Therefore, a liquid with a lower vapor pressure will have a higher boiling point.

- **Summary**

- The phenomenon is due to the fact that strong intermolecular forces reduce vapor pressure by making it harder for molecules to escape the liquid phase.
  - As a result, more heat (a higher temperature) is required to elevate the vapor pressure to atmospheric pressure, which in turn results in a higher boiling point.
Liquids with stronger intermolecular forces have lower vapor pressures and higher boiling points because the molecules require more energy to escape into the gas phase.

Liquid with a lower vapor pressure has a higher boiling point. Explain this
phenomenon in term of the relationship between vapor pressure and
intermolecular forces.

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