Question

which statement(s) are true for a liquid that is at its boiling point? select all that apply a the vapor pressure of the liquid and the atmospheric pressure are equal. b the molecules all throughout the liquid have enough kinetic energy to enter the gas phase. c the vapor pressure of the liquid is lower than the atmospheric pressure. d the temperature is 100°c or higher.

Explanation:

• Option a: By definition, the boiling point of a liquid is when its vapor pressure equals the atmospheric pressure. So, this statement is true.
• Option b: At the boiling point, molecules throughout the liquid gain enough kinetic energy to escape into the gas phase (not just surface - molecules as in evaporation). This statement is true.
• Option c: If the vapor pressure were lower than the atmospheric pressure, the liquid would not boil. Boiling occurs when vapor pressure equals atmospheric pressure. So, this statement is false.
• Option d: The boiling point of a liquid is substance - specific. For example, ethanol has a boiling point of \(78.37^{\circ}C\) at standard atmospheric pressure. So, the boiling point is not necessarily \(100^{\circ}C\) or higher. This statement is false.

Answer:

A. The vapor pressure of the liquid and the atmospheric pressure are equal.
B. The molecules all throughout the liquid have enough kinetic energy to enter the gas phase.