[Sheryl]

Question: A solid substance has a vapor pressure of 100 mmHg at the melting point (100C). Assuming an atmospheric pressure of 760 mmHg, describe the behavior of this solid as the temperature is raised from room temperature to its melting point.

I know that the answer to this question is that the solid vaporizes as it is heated, then when it gets to the melting point it melts and will still vaporize.  I don't understand why.

It seems to me that the vapor pressure of 760 is too high to allow vaporization, that it should be below 10 mmHg for this to happen.   Where is my reasoning wrong?  And if it vaporizes, why wouldn't it completely vaporize before hits the melting point?

Thanks from Sheryl

[Yggdrasil]

Sublimation or vaporization take place when the vapor pressure of the solid or liquid exceeds atmospheric pressure.  Also, I think you may have confused the pressures.  The vapor pressure is 100mmHg and the atmospheric pressure is 760mmHg.

[Sheryl]

You're absolutely right.  I had the vapor pressures reversed in my mind.

Thank you,

Sheryl