boiling point and atmospheric pressure

[nickelbackfan]

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Why is there a positive correlation between the two? IE as atmospheric pressure increases, the BP of a solution will increase. TBR talks about this but I don't quite get it.

Thanks

 

[Jepstein30]

Why is there a positive correlation between the two? IE as atmospheric pressure increases, the BP of a solution will increase. TBR talks about this but I don't quite get it.

Thanks

I don't fully understand it either but my take on it is a solution boils once its vapor pressure equals atmospheric pressure (why? I don't know..).

So if vapor pressure decreases, you are getting farther away from boiling and hence an increased boiling point.

If vapor pressure increases, you are getting closer to boiling = lower BP.

 

[BB8730]

Why is there a positive correlation between the two? IE as atmospheric pressure increases, the BP of a solution will increase. TBR talks about this but I don't quite get it.

Thanks

Think of it this way. In a liquid, molecules are close together. In a gas, the molecules are very spread out. Boiling is the act of those molecules separating from each other and spreading out. The harder it is for those molecules to separate, the higher the boiling point will be. That's why the stronger the intermolecular forces, the higher the boiling point. The same thing can be applied to atmospheric pressure. Higher atmospheric pressure makes it harder for those molecules to separate and spread out, thus a higher atmospheric pressure leads to a higher BP.

 

[nickelbackfan]

Think of it this way. In a liquid, molecules are close together. In a gas, the molecules are very spread out. Boiling is the act of those molecules separating from each other and spreading out. The harder it is for those molecules to separate, the higher the boiling point will be. That's why the stronger the intermolecular forces, the higher the boiling point. The same thing can be applied to atmospheric pressure. Higher atmospheric pressure makes it harder for those molecules to separate and spread out, thus a higher atmospheric pressure leads to a higher BP.

Can you think of it like this; the higher ATM act as a "pushing" force against the liquid, thus preventing the molecules from diffusing out, hence making the BP higher?

 

[BB8730]

Can you think of it like this; the higher ATM act as a "pushing" force against the liquid, thus preventing the molecules from diffusing out, hence making the BP higher?

Yep! I'm not sure if that's the perfect technical explanation, but that's basically how I view it.

 

[sports]

Boiling happens when vapour pressure is equal to atmospheric pressure. A high vapour pressure means that something boils easily. If you increase atmospheric pressure, it will take a lot longer to reach a vapour pressure to match that, making it harder to boil, meaning that its boiling point would increase.

Think of of it this way: Atmospheric pressure opposes boiling, increasing pressure being exerted on a liquid will make it harder for the molecules to escape as a gas.