What Determines Equilibrium in a Liquid-Vapor System?

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SUMMARY

The equilibrium between a liquid and its vapor at the boiling point is characterized by equal total energy (C) in both phases. The discussion clarifies that intermolecular forces (A) are significantly stronger in liquids than in gases, ruling it out. Kinetic energy (D) is not equal due to the temperature dependence of gases, leaving total energy as the correct answer. The relationship between potential energy and total energy is also explored, emphasizing the dominance of kinetic energy in gases.

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  • Understanding of thermodynamic concepts, particularly phase equilibrium.
  • Familiarity with kinetic and potential energy principles.
  • Knowledge of the properties of liquids and gases at boiling points.
  • Basic grasp of intermolecular forces and their effects on phase states.
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  • Study the principles of phase transitions in thermodynamics.
  • Learn about the relationship between temperature and kinetic energy in gases.
  • Explore the concept of total energy in thermodynamic systems.
  • Investigate intermolecular forces and their impact on physical states of matter.
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Homework Statement


A liquid is in equilibrium with its vapor at its boiling point. On an average, the molecules in the two phases have equal:
(A) inter-molecular forces
(B) potential energy
(C) total energy
(D) kinetic energy

Homework Equations

The Attempt at a Solution


I know (A) is wrong as intermolecular forces in liquids are much more than those in gases. However, I'm confused between (B) (C) and (D). I know in gases KE is directly proportional to temperature. I'm not really sure about anything beyond this.
 
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Okay --- it's not KE. That leaves PE and TE; do you think TE might be related more to KE than PE? Or, less?
 
Why isn't it KE? Shouldn't KE also be proportional to temperature in liquids?
And I don't know whether TE might be more related to KE or PE.
 

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