Answer:
59.9 g/mol is the molar mass for the solute
Explanation:
Lowering vapor pressure → ΔP = P° . Xm
P° → Vapor pressure of pure solvent
ΔP = P° - Vapor pressure of solution
Xm = Mole fraction of solute
17.54 Torr - 17.344 Torr = 17.54 Torr . Xm
0.196 Torr / 17.54 Torr = Xm → 0.0112
These are the moles of solute / Total moles
Total moles = Moles of solute + Moles of solvent
We determine the moles of solvent → 150 g . 1mol/ 18 g = 8.33 moles
Now we can make this equation:
0.0112 = Moles of solute / Moles of solute + 8.33 mol
0.0112 Moles of solute + 0.0933 = Moles of solute
0.0933 = Moles of solute - 0.0112 Moles of solute
0.0933 = 0.9888 moles of solute → 0.0933 / 0.9888 = 0.0947 moles
Finally we can determine the molar mass (mol/g)
5.678 g / 0.0947 mol = 59.9 g/mol
