Dr. Romano, I have a question

[marianirj]

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Can you explain to me why boiling point is inversely proportional to vapor pressure?

Thanks,
Bob

 

[Lonely Sol]

Can you explain to me why boiling point is inversely proportional to vapor pressure?

Thanks,
Bob Mariani (in your 2-4 pm class)

I hope you don't mind if I try to explain, maybe Dr. Romano can correct me if I am wrong but here is what I think:

Well, first you should know that vapor pressure is equal to the pressure in the system. So, from le chatelier's principle we know that as pressure is exerted on the system, the temperature of the system rises. There for as vapor pressure increases, boiling point decreases. Just think of it as a piston in the car, when piston is compressed, then the temperature inside the piston rises high enough to cause a combustion rxn.

*I might be completely wrong, This is the best reasoning I can come up with, without searching the internet.

 

[bkim]

I hope you don't mind if I try to explain, maybe Dr. Romano can correct me if I am wrong but here is what I think:

Well, first you should know that vapor pressure is equal to the pressure in the system. So, from le chatelier's principle we know that as pressure is exerted on the system, the temperature of the system rises. There for as vapor pressure increases, boiling point decreases. Just think of it as a piston in the car, when piston is compressed, then the temperature inside the piston rises high enough to cause a combustion rxn.

*I might be completely wrong, This is the best reasoning I can come up with, without searching the internet.

Also, high vapor pressure means weak intermolecular forces(or low viscosity) -> low boiling point.

Low vapor pressure -> Strong intermolecular forces ( high viscosity) -> high B.P.

 

[artsyme]

I think about it like this:

A substance boils when the vapor pressure = atmospheric pressure.
If the vapor pressure is high, not many molecules of liquid need to escape into the gas/vapor phase(remember the aim is to get the vapor pressure equal to the atmospheric pressure). Thus, not as much heat (temperature increase) needs to be added for this to be achieved.