[fk378]

A 4.7-L sealed bottle containing 0.33 g of liquid ethanol, C2H6O, is placed in a refrigerator and reaches equilibrium with its vapor at -11 degrees C.

a) What is the mass of ethanol present in the vapor?
b) When the container is removed and warmed to room temperature, 20 degrees C, will all the ethanol vaporize?
c) How much liquid ethanol would be present at 0 degrees C?

The vapor pressure of ethanol is 10 torr at -2.3 degrees C and 40 torr at 19 degrees C.
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My attempt:

a) I have the mass of the substance, .33 grams and I know the L, so I can figure out the molarity. But I don't know if that's the right approach. 

For the rest of the problem, I don't know how to begin or how to figure it out.... Any suggestions would be appreciated, thank you!!

[Rabn]

Molarity is a description of moles of substance per liter of solution.  The problems states that you have liquid ethanol, in other words you should consider it to be pure ethanol. What have you learned about how liquids and vapors relate?