A substance with large intermolecular forces will have which of the following?
A) high boiling point
B) low vapor pressure
C) high critical temperatures and pressures
D) high heats of fusion and vaporization
E) all of the above
The correct answer and explanation is :
The correct answer is E) all of the above.
Explanation:
Intermolecular forces (IMFs) are the forces of attraction between molecules. The strength of these forces greatly affects the physical properties of a substance. A substance with large intermolecular forces will exhibit the following properties:
- High Boiling Point:
The boiling point is the temperature at which a liquid turns into a gas. When intermolecular forces are strong, more energy (heat) is required to break these forces and convert the liquid into a gas. Therefore, substances with strong IMFs, such as hydrogen bonding (e.g., water) or van der Waals forces in large molecules, have high boiling points. - Low Vapor Pressure:
Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase. A substance with strong intermolecular forces will have fewer molecules escaping into the gas phase at a given temperature, resulting in a lower vapor pressure. This is why liquids like water have much lower vapor pressures compared to substances with weaker IMFs, such as ethanol or acetone. - High Critical Temperatures and Pressures:
The critical temperature is the highest temperature at which a gas can be liquefied by pressure, and the critical pressure is the pressure required to liquefy a gas at its critical temperature. Strong IMFs mean that more energy is needed to overcome these forces, leading to higher critical temperatures and pressures. - High Heats of Fusion and Vaporization:
The heat of fusion is the energy required to convert a solid into a liquid, while the heat of vaporization is the energy needed to convert a liquid into a gas. Strong IMFs require more energy to break, so substances with large IMFs have high heats of fusion and vaporization.
Since all these properties are influenced by strong IMFs, the correct answer is E) all of the above.
