Answer:
x = 0.94
Step-by-step explanation:
From Raoult´s law of partial pressure in solution we know
P methanol = X methanol Pº methanol
where P methanol is the partial pressure of methanol in solution, X is the mole fraction of methanol and Pº is its pure vapor pressure.
Given the equation above we can solve for X , mole fraction:
X methanol = P methanol / Pº methanol = 713.8 torr / 760 torr
( key here is that the normal boiling point is defined as the temperature at which a substance boil at one atmosphere pressure (760 torr) which was stated in the question)
X methanol = 0.94