0
$\begingroup$

As we know, evaporation occurs when a liquid molecule has a kinetic energy that is greater than the minimum amount of energy needed to overcome the intermolecular attractive forces holding it in the liquid, allowing it to escape into the vapor phase.

We also know that the pressure of a gas is a measure of the average linear momentum of the moving molecules of a gas.

Does pressure of the gas above the liquid have any impact on the number of liquid molecules escaping into the vapor phase? Is there a gas pressure (linear momentum of gas molecules) high enough that a direct collision of a gas molecule with a liquid molecule would prevent the liquid molecule from vaporizing?

$\endgroup$

1 Answer 1

0
$\begingroup$

Does pressure of the gas above the liquid have any impact on the number of liquid molecules escaping into the vapor phase?

Yes. If the pressure is low enough, the net rate at which molecules in the liquid will leave the liquid phase will be so great the liquid will boil.

Above that pressure, the rapidity with which gaseous molecules of the liquid species are moved away from near the surface will affect the rate of evaporation.

Molecules of the liquid species that do NOT move away from the surface may be reabsorbed into the liquid phase, thus reducing the rate of evaporation.

The two means by which molecules move away from the surface are convection (bulk flow) and diffusion. The greater the number of non-liquid-species molecules per volume, the lower the rate of diffusion.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.