Vapor Pressure

[Contach]

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I'm so sure I saw this question before.. but I did a search and went back 3 pages.. but couldnt find it..

If someone can explain why D.. would help - thanks. I said A because if you add liquid, you are increasing the mole fraction of the liquid and thus Vapor pressue goes up. and since Vp = (Vp)pure * mole fraction

Increasing the amount of liquid in a sealed container will cause the vapor pressure of the liquid to

increase, regardless of the identity of the liquid.
increase, if the liquid is sufficiently volatile.
decrease, regardless of the identity of the liquid.
remain the same, regardless of the identity of the liquid.
decrease, if the liquid is sufficiently volatile.

 

[Sunshine2]

I think vapor pressure is just the liquids ability to evaporate. It is related to temperature but not volume so that would make D correct. Sound reasonable?

 

[iverson3504]

why do you think that adding liquid would increase the mole fraction... think of a 10 gallon drum of H2O, filled halfway. now add two more gallons of water, does the mole fraction change? how bout if you fill it up to the top?

also, vapor pressure depends on intra molecular forces, which do not change if you simply add more liquid

 

[Contach]

ohh. you know what I just realized.. in the question stem it says it's liquid.. this means 100% of the same substance meaning there are no ions or other particles in it.

If it said solution in the question stem then I would be correct.. right?

 

[joonkimdds]

The wiki says
"The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point (i.e., the boiling point at atmospheric pressure) of the liquid."

If we add something to the pure water, the boiling point increases.
so if we think the vapor pressure is the opposite(inversely proportional) of BP, then i think VP should decrease as we add more ions or other particles in it. And if what I think is right, then I think C should be the answer(assuming that we added other particles).