Finding the mole fraction

[Katelyn]

Acetone, C3H6O, is the main ingredient of nail polish remover.  A solution is made by adding 35.0 mL of aceton (density=0.790 g/mL) to 50.0 mL of ethyl alcohol, C2H6O (density=0.789 g/mL).  Assuming volumes are additive, calculate

a. The volume percent of acetone in the solution:   

b. The volume percent of ethyl alcohol in the solution: 

c. The mole fraction of acetone in the solution:

Help! I don't get how to get the mole fraction

[kingchemist]

Use density of acetone to find the mass of 35.0 mL. (mass = density x volume)
Use the molar mass of acetone to find the number of moles of acetone in the calculated mass (no. of moles = mass/molar mass)

Do the same for ethyl alcohol.

Add moles of acetone to moles of ethyl alcohol to give total moles present.
Mole fraction of acetone = moles of acetone/total moles.
Mole fraction of ethyl alcohol = moles of ethyl alcohol/total moles