Question

What do we mean when we say a liquid is volatile? Do volatile liquids have large or small vapor pressures? What types of intermolecular forces occur in highly volatile liquids?

Short answer

A liquid is considered volatile when it has a tendency to vaporize or evaporate easily at a given temperature. Volatile liquids have large vapor pressures, which allows them to vaporize more easily. Highly volatile liquids possess weak intermolecular forces, such as dispersion forces or weaker dipole-dipole interactions. Strong hydrogen bonding is typically not present in highly volatile liquids, as it would reduce volatility.

Step-by-step solution

Defining Volatility for Liquids

When we say a liquid is volatile, it means that the liquid has a tendency to vaporize or evaporate easily at a given temperature. Volatile liquids have a higher rate of vaporization compared to non-volatile liquids at the same temperature.

Vapor Pressure in Volatile Liquids

Volatile liquids have large vapor pressures. Vapor pressure is defined as the pressure exerted by the gas phase of a substance in equilibrium with its liquid phase. The larger the vapor pressure, the more the liquid evaporates into the gas phase. Therefore, volatile liquids have higher vapor pressures, enabling them to vaporize more easily.

Intermolecular Forces in Highly Volatile Liquids

Highly volatile liquids usually have weak intermolecular forces, allowing the molecules to escape the liquid phase more easily and become vapor. The types of intermolecular forces that occur in highly volatile liquids would include one or more of the following: 1. Dispersion forces (also known as London dispersion forces or van der Waals forces): These are weak intermolecular forces that arise due to temporary dipole moments in molecules without a permanent dipole, such as nonpolar molecules like methane (CH4). 2. Dipole-dipole interactions: These occur between neighboring polar molecules due to the attraction between their positive and negative poles. However, in highly volatile liquids, these interactions are generally weaker compared to less volatile liquids, allowing for easier vaporization. 3. Hydrogen bonding: Hydrogen bonding, a strong type of dipole-dipole interaction, occurs between molecules containing a hydrogen atom bonded to a highly electronegative element (e.g., oxygen, nitrogen, or fluorine). However, highly volatile liquids typically do not exhibit strong hydrogen bonding, as it would require more energy to break these intermolecular forces, thus reducing volatility.