[avcww]

Hello everyone! Bear with me if i missed the topic i'm about to raise. I'm new and i did try to find solutions to my problem in the previous posts but could not. So i'm trying to ask now 

I'm having a review for the Board Exams (PRC) and it's been awhile since i graduated form college, so my brain is a bit rusty already  please feel free to enlighten me on this topic...

Problem:  A 750-ml bottle of alcoholic beverage is labeled 100 proof. Assume a headspace of 100 ml and that the rest of the solution is only water.
 given: pressure of  pure EtOH @ 25 deg = 7.87 kPa
          density of EtOH is 0.79 mg/ml

Questions: 1. calculate mole fraction of EtOH
               2. calculate P EtOH over the solution, assuming solution is ideal
               3. if P H2O is 23.76 mmHg, find P total.


I know that for me to solve the mole fraction i will use the density but i am confused of the volume to use. Does the headspace of 100 ml mean i have to use 750-100 volume and proceed to use the conversion on proof?

Secondly, can i use Raoul't law here or dalton's law? in calculating for the pressure of EtOH over the solution? is it different from vapor pressure of EtOH?

Please enlighten me? Thank you in advance...