Colligative property question

[Piepiesuperpie]

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So according to Raoult's Law, impurities will decrease the vapor pressure. Yet another colligative property is that the boiling point will increase. If vapor pressure decreases with impurities, shouldn't boiling point also decrease?

 

[DrillSoHard]

This might clarify things up for you.

http://forums.studentdoctor.net/archive/index.php/t-420849.html

 

[FeralisExtremum]

Boiling point and vapor pressure are directly related - they are inversely proportional.

Think about it conceptually: when you boil something, it is converting from liquid to gas phase and escaping the container. Vapor pressure is essentially measuring how much pressure the escaping gas is exerting.

If you raise the boiling point, it is harder to make something boil - which means that less of it is escaping as gas, and your vapor pressure is lower.

If you lower the boiling point, it is easier to boil, so more of it is escaping as gas - exerting more (vapor) pressure.

Keep in mind - a substance doesn't need to be boiling to exert vapor pressure.

 

[helloworld9]

So according to Raoult's Law, impurities will decrease the vapor pressure. Yet another colligative property is that the boiling point will increase. If vapor pressure decreases with impurities, shouldn't boiling point also decrease?

According to chad's videos, Vapor Pressure is inversely related to Boiling Point (and Melting Point).

If you think about it conceptually, if the boiling point is low, assuming it is a liquid, it will turn into vapor more readily, making the vapor pressure high!

EDIT: I just saw Ferali's response and it's basically the same thing haha sorry! guess we posted at the same time

 

[hope_to_match]

yes what everyone else said...bp and vp are inversely proportional...think about this: when intermolecular forces increases everything increases (mp, bp, viscosity etc...but vapor pressure decreases)