How many grams of C12H22O11 must be added to 552 g of H2O to give a solution with..?

Question

a vapor pressure 2 mmHg less than that of pure water at 20 degree? ( the vapor pressure of water at 20 degree is 17.5 mmHg)

Answer 1

15.5 = 17.5 X

X = mole fraction water = 0.886

Moles water = 552 / 18 = 30.7

0.886 = 30.7 / 30.7 + moles C12H22O11

27.2 + 0.886 moles sucrose = 30.7

3.5 = 0.886 moles sucrose

moles sucrose =  3.95

Mass = 3.95 mol x 342.3 =1352 g