quick semantics question: vapor P/ bp

[SaintJude]

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lowering the vapor pressure of a substance = raising boiling point

lowering the atmospheric pressure = lowering boiling point

👍 👎 ?

 

[gettheleadout]

lowering the vapor pressure of a substance = raising boiling point

lowering the atmospheric pressure = lowering boiling point

👍 👎 ?

Well, vapor pressure is inversely proportional to IMF (intermolecular forces), which is directly proportional to boiling point, so a substance with a lower vapor pressure will have a higher boiling point.

Lower VP = higher IMF = higher b.p.

Normal boiling point is defined as the point where vapor pressure is equal to atmospheric pressure, so with a lower atmospheric pressure a lower vapor pressure is needed to "boil."

Normal b.p. = (VP = atmospheric P) so therefore lower atmospheric P = lower VP to boil = lower b.p.

I believe your statements are correct.

 

[chiddler]

agree sounds correct.

 

[BA11]

Yes, you are correct on both counts

 

[MrNeuro]

Well, vapor pressure is inversely proportional to IMF (intermolecular forces), which is directly proportional to boiling point, so a substance with a lower vapor pressure will have a higher boiling point.

Lower VP = higher IMF = higher b.p.

Normal boiling point is defined as the point where vapor pressure is equal to atmospheric pressure, so with a lower atmospheric pressure a lower vapor pressure is needed to "boil."

Normal b.p. = (VP = atmospheric P) so therefore lower atmospheric P = lower VP to boil = lower b.p.

I believe your statements are correct.

👍

 

[MedPR]

lowering the vapor pressure of a substance = raising boiling point

lowering the atmospheric pressure = lowering boiling point

👍 👎 ?

Yes and increasing volatility = decreasing boiling point.

The following is mostly conceptual for me, so ignore if you already have this down.

Vapor pressure is the pressure in the gas phase. Since boiling point is when vapor pressure is greater than atmospheric pressure, the lower the vapor pressure is, the more you have to increase it to get it higher than Patm, thus the greater your boiling point has to be. High vapor pressure means you are relatively closer to Patm than low vapor pressure, so you don't have to increase the temperature very much since by PV=nRT, all else constant, as you increase Temp you also increase Pressure.