Vapor Pressure & Boiling Point

[G1SG2]

Hey, if the boiling point of a substance is lower than water, should the vapor pressure of that substance near its boiling point be less than that of water or higher than that of water? I have here in my notes that it should be less than that of water but shouldn't it be higher than water, considering water has a higher boiling point, and thus reaches the required level of vapor pressure at a higher temperature?

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[mflee]

Well at each substance's boiling points, their VP is going to be the same as atmospheric pressure. So their VP's at boiling should be the same. The TEMPERATURE of substance w/ lower BP will be lower than water's TEMPERATURE at bp. Maybe that's what you meant in your notes?

Someone correct me if I'm wrong

 

[G1SG2]

Well at each substance's boiling points, their VP is going to be the same as atmospheric pressure. So their VP's at boiling should be the same. The TEMPERATURE of substance w/ lower BP will be lower than water's TEMPERATURE at bp. Maybe that's what you meant in your notes?

Someone correct me if I'm wrong

That's what I thought, too, initially but got bogged down in wording since it says NEAR its boiling point. I'll have to double check, I think I got it from the TPR PS book.

 

[badmintondr]

So, to mflee, he says the boiling point of "its" <--referring to the substance with lower BP than water so I don't think your justification would work.

But ya, G1, I'm positive you should say that it should have a higher VP due to lower BP.

 

[G1SG2]

So, to mflee, he says the boiling point of "its" <--referring to the substance with lower BP than water so I don't think your justification would work.

But ya, G1, I'm positive you should say that it should have a higher VP due to lower BP.

Got it, thanks. I think I should've been more clear about the scenario-we have water and substance x. Substance X is boiling already and water is not, since it has a higher BP. Substance X has the higher vapor pressure. Thanks.

 

[badmintondr]

NP! (Lol the day before my MCAT...and I'm resting..by surfing the SDN boards for mcat stuff) hahahah

 

[G1SG2]

NP! (Lol the day before my MCAT...and I'm resting..by surfing the SDN boards for mcat stuff) hahahah

Good luck!!

 

[mflee]

NP! (Lol the day before my MCAT...and I'm resting..by surfing the SDN boards for mcat stuff) hahahah

me too!!

 

[badmintondr]

lol good luck to both of us! >.< im scurred